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Document and Entity Information - shares	3 Months Ended
Document and Entity Information - shares	Mar. 31, 2018	May 01, 2018
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Mar. 31, 2018
Document Fiscal Year Focus	2018
Document Fiscal Period Focus	Q1
Trading Symbol	FLGT
Entity Registrant Name	Fulgent Genetics, Inc.
Entity Central Index Key	0001674930
Current Fiscal Year End Date	--12-31
Entity Filer Category	Smaller Reporting Company
Entity Common Stock, Shares Outstanding		17,889,082

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Current assets
Cash and cash equivalents	$ 5,274	$ 6,490
Marketable securities	23,211	19,994
Trade accounts receivable, net of allowance for doubtful accounts of $335 and $287, as of March 31, 2018 and December 31, 2017, respectively	4,969	4,005
Other current assets	2,621	2,438
Total current assets	36,075	32,927
Marketable securities, long term	10,285	14,883
Equity method investments	1,692	1,937
Fixed assets, net	6,853	7,272
Deferred tax asset	505	126
Other long-term assets	30	39
Total assets	55,440	57,184
Current liabilities
Accounts payable	1,347	2,089
Accrued liabilities	1,062	911
Total current liabilities	2,409	3,000
Other long-term liabilities	6	6
Total liabilities	2,415	3,006
Commitments and contingencies (Note 8)
Stockholders’ equity
Common stock, $0.0001 par value per share, 50,000 shares authorized, 17,876 and 17,847 shares issued and outstanding at March 31, 2018 and December 31, 2017, respectively.	2	2
Preferred stock, $0.0001 par value per share, 1,000 shares authorized, no shares issued or outstanding at March 31, 2018 and December 31, 2017
Additional paid-in capital	112,431	111,884
Accumulated other comprehensive income (loss)	(87)	(44)
Accumulated deficit	(59,321)	(57,664)
Total stockholders’ equity	53,025	54,178
Total liabilities and stockholders’ equity	$ 55,440	$ 57,184

Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Statement Of Financial Position [Abstract]
Allowance for doubtful accounts receivable	$ 335	$ 287
Common stock, par value	$ 0.0001	$ 0.0001
Common stock, shares authorized	50,000,000	50,000,000
Common stock, shares issued	17,876,000	17,847,000
Common stock, shares outstanding	17,876,000	17,847,000
Preferred stock, par value	$ 0.0001	$ 0.0001
Preferred stock, shares authorized	1,000,000	1,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0

Condensed Consolidated Statements of Operations (unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Income Statement [Abstract]
Revenue	$ 4,653	$ 5,306
Cost of revenue	2,772	1,859
Gross profit	1,881	3,447
Operating expenses:
Research and development	1,458	851
Selling and marketing	1,130	891
General and administrative	1,487	1,486
Total operating expenses	4,075	3,228
Operating income (loss)	(2,194)	219
Interest and other income (expense)	95	119
Income (loss) before income taxes and equity loss in investee	(2,099)	338
Provision for (benefit from) income taxes	(434)	106
Income (loss) before equity loss in investee	(1,665)	232
Equity loss in investee	(245)	0
Net income (loss)	$ (1,910)	$ 232
Net income (loss) per common share:
Basic	$ (0.11)	$ 0.01
Diluted	$ (0.11)	$ 0.01
Weighted-average common shares:
Basic	17,864	17,676
Diluted	17,864	18,178

Condensed Consolidated Statements of Comprehensive Income (Loss) (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Statement Of Income And Comprehensive Income [Abstract]
Net income (loss)	$ (1,910)	$ 232
Other comprehensive income (loss), net of tax:
Foreign currency translation gain (loss)	22
Net unrealized gain (loss) on marketable securities	(65)	(18)
Comprehensive income (loss)	$ (1,953)	$ 214

Condensed Consolidated Statements of Stockholders' Equity (unaudited) - 3 months ended Mar. 31, 2018 - USD ($) $ in Thousands	Total	Stockholders' Equity	Additional Paid-In Capital	Accumulated Other Comprehensive Loss	Accumulated Deficit
Beginning Balance at Dec. 31, 2017	$ 54,178	$ 2	$ 111,884	$ (44)	$ (57,664)
Beginning Balance, Shares at Dec. 31, 2017	17,847,000	17,847,000
Equity-based compensation	$ 545		545
Exercise of common stock options	2		2
Exercise of common stock options, Shares		5,000
Restricted stock awards, Shares		24,000
Cumulative effect of accounting change	327				327
Cumulative tax effect of accounting change	(74)				(74)
Other comprehensive income, net	(43)			(43)
Net income (loss)	(1,910)				(1,910)
Ending Balance at Mar. 31, 2018	$ 53,025	$ 2	$ 112,431	$ (87)	$ (59,321)
Ending Balance, Shares at Mar. 31, 2018	17,876,000	17,876,000

Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Cash flow from operating activities:
Net income (loss)	$ (1,910)	$ 232
Adjustments to reconcile net income (loss) to net cash provided by (used in) operating activities:
Equity-based compensation	545	565
Depreciation and amortization	516	412
Loss on disposal of fixed asset	51
Amortization of premium of marketable securities	82	95
Provision for bad debt	48
Deferred taxes	(434)
Equity loss in investee	245	0
Other	28
Changes in operating assets and liabilities:
Accounts receivable	(713)	(237)
Other current assets	(125)	(343)
Accounts payable	218	(241)
Taxes payable		106
Accrued liabilities	158	919
Net cash (used in) provided by operations	(1,291)	1,508
Cash flow from investing activities:
Purchases of fixed assets	(1,116)	(90)
Purchase of marketable securities	(4,683)	(2,780)
Maturities of marketable securities	5,850	1,000
Net cash provided by (used in) investing activities	51	(1,870)
Cash flow from financing activities:
Payment of initial public offering costs		(801)
Proceeds from exercise of stock options	2
Net cash provided by (used in) financing activities	2	(801)
Effect of exchange rate changes on cash and cash equivalents	22
Net decrease in cash	(1,216)	(1,163)
Cash balance at beginning of period	6,490	7,897
Cash balance at end of period	5,274	6,734
Supplemental disclosures of non-cash investing and financing activities:
Fixed assets included in accounts payable	$ 6	$ 11

Overview and Basis of Presentation	3 Months Ended
Overview and Basis of Presentation	Mar. 31, 2018
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Overview and Basis of Presentation	Note 1. Overview and Basis of Presentation The accompanying condensed consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America (“U.S. GAAP”). These financial statements include the assets, liabilities, revenues and expenses of all wholly-owned subsidiaries and entities in which the Company has a controlling financial interest or is deemed to be the primary beneficiary. In determining whether the Company is the primary beneficiary of an entity, the Company applies a qualitative approach that determines whether it has both (1) the power to direct the economically significant activities of the entity and (2) the obligation to absorb losses of, or the right to receive benefits from, the entity that could potentially be significant to that entity. The Company uses the equity method to account for its investments in entities that it does not control, but in which it has the ability to exercise significant influence over operating and financial policies. All significant intercompany accounts and transactions are eliminated from the accompanying condensed consolidated financial statements. Nature of the Business Fulgent Genetics, Inc., together with its subsidiaries (collectively referred to as the “Company,” unless otherwise noted or the context otherwise requires), is a growing technology company with an initial focus on offering comprehensive genetic testing to provide physicians with clinically actionable diagnostic information they can use to improve the quality of patient care (the “Diagnostics business”). The Company has developed a proprietary technology platform that allows it to offer a broad and flexible test menu and continually expand and improve its proprietary genetic reference library. The Company’s current test menu offers single-gene tests and pre-established, multi-gene, disease-specific panels that collectively test for many genetic conditions, including various cancers, cardiovascular diseases, neurological disorders and pediatric conditions. The Company’s existing customer base consists primarily of hospitals and medical institutions, which are frequent and high-volume users of genetic tests and which typically pay the Company directly for its tests. Unaudited Interim Financial Information The accompanying interim condensed consolidated financial statements have been prepared on the same basis as the Company’s audited consolidated financial statements as of and for the fiscal year ended December 31, 2017, which are included in the Company’s annual report on Form 10-K filed with the Securities and Exchange Commission on March 19, 2018 (the “2017 Annual Report”), and, in the opinion of management, include all adjustments, which are normal and recurring in nature, necessary for a fair presentation of the Company's financial position and results of operations. Operating results for interim periods are not necessarily indicative of the results that may be expected for a full fiscal year or any other period. The accompanying condensed consolidated balance sheet as of December 31, 2017 has been derived from the Company’s audited consolidated financial statements at that date but does not include all of the disclosures required by U.S. GAAP. As such, the information included in this quarterly report on Form 10-Q should be read in conjunction with the Company’s audited consolidated financial statements included in the 2017 Annual Report, including the notes thereto. Consolidated Statements of Cash Flows Error Subsequent to the issuance of its consolidated financial statements for the three-month period ended March 31, 2017, the Company discovered an error in the Consolidated Statements of Cash Flows. A cash payment of $801,000, for costs in connection with the Company’s initial public offering was previously reported within changes in accounts payable and accrued liabilities under operating activities in the Company’s consolidated statement of cash flows for the three months ended March 31, 2017. Accordingly, the Company restated such consolidated statement of cash flows to correct the misstatement, which increased net cash provided by operating activities to $1.5 million, previously reported as $707,000, and increased net cash used in financing activities to $801,000, previously reported as zero. The Company evaluated the materiality of this misstatement from quantitative and qualitative perspectives and concluded that it was immaterial to the prior periods.

Summary of Significant Accounting Policies

3 Months Ended

Mar. 31, 2018

Accounting Policies [Abstract]

Summary of Significant Accounting Policies

Note 2. Summary of Significant Accounting Policies

See the summary of the Company’s significant accounting policies set forth in the notes to its consolidated financial statements included in the 2017 Annual Report.

Use of Estimates

The preparation of consolidated financial statements in conformity with U.S. GAAP requires management to make certain estimates, judgments and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements, as well as the reported amounts of revenue and expenses during the reporting periods. These estimates, judgments and assumptions are based on historical data and experience available at the date of the accompanying condensed consolidated financial statements, as well as various other factors management believes to be reasonable under the circumstances. Actual results could differ from these estimates.

On an on-going basis, management evaluates its estimates, primarily those related to: (i) revenue recognition criteria, (ii) accounts receivable and allowances for doubtful accounts, (iii) the useful lives of fixed assets, (iv) estimates of tax liabilities and (v) equity method investments.

Foreign Currency Translation and Foreign Currency Transactions

The Company translates the assets and liabilities of its non-U.S. dollar functional currency subsidiaries into U.S. dollars using exchange rates in effect at the end of each period. Expenses for these subsidiaries are translated using rates that approximate those in effect during the period. Gains and losses from these translations are recognized in foreign currency translation included in other comprehensive income (loss) in the accompanying condensed consolidated statements of stockholders’ equity. The Company’s subsidiaries that use the U.S. dollar as their functional currency remeasure monetary assets and liabilities at exchange rates in effect at the end of each period, and inventories, property and nonmonetary assets and liabilities at historical rates. Income from these remeasurements were $22,000 in the first quarter of 2018, and gains and losses from these remeasurements were not significant in the in the first quarter of 2017.

Concentration of Customers

In certain periods, a small number of customers has accounted for a significant portion of the Company’s revenue. In the first quarter of 2018, after aggregating customers that are under common control or are affiliates, one customer contributed 13% of our revenue. In the first quarter of 2017, after aggregating customers that are under common control or are affiliates, four customers contributed 15%, 14%, 11% and 10% of our total revenue, respectively, of which the first two customers represent one customer for concentration disclosure purposes as they are managed by the same foreign governmental body.

Revenue Recognition

Effective January 1, 2018, the Company began recognizing revenue in accordance with FASB ASC Topic 606, Revenue from Contracts with Customers (“ASC 606”). The Company adopted ASC 606 utilizing the modified retrospective method, meaning the cumulative effect of applying the standard was recognized to opening retained earnings as of January 1, 2018. To reflect the impact of the adoption, the Company recorded an adjustment of $327,000 to beginning accumulated deficit and accounts receivable and an adjustment of ($74,000) to beginning accumulated deficit and deferred taxes. ASC 606 provides for a five-step model that includes identifying the contract with a customer, identifying the performance obligations in the contract, determining the transaction price, allocating the transaction price to the performance obligations, and recognizing revenue when, or as, an entity satisfies a performance obligation.

Performance Obligations

Genetic Testing Services

Clinical – Institutional

Our clinical institutional contracts included within genetic testing services typically have a single performance obligation to deliver genetic testing services to the ordering facility or patient. Some arrangements involve the delivery of genetic testing services to research institutions, which we refer to as “sequencing as a service.” In arrangements with hospitals, medical or research institutions, the transaction price is stated within the contract and is therefore fixed consideration. For most of our clinical volume, we identified the hospital, medical, or research institution as the customer in Step 1 of the model and have determined a contract exists with the institution in Step 1. As these contracts typically have a single performance obligation, no allocation of the transaction price is required in Step 4 of the model. Control over genetic testing services is transferred to our ordering institutions at a point in time. Specifically, we determined the customer obtains control of the promised service upon our delivery of test results.

Clinical – Insurance

Our clinical insurance contracts included within genetic testing services typically have a single performance obligation to deliver genetic testing services to the ordering facility or patient. For most of our clinical insurance volume, we identified the patient as the customer in Step 1 of the model and have determined a contract exists with the patient in Step 1. In arrangements with insurance patients, the transaction price is stated within the contract, however, we accept payments from third-party payors that are less than the contractually stated price and is therefore variable consideration. In developing the estimate of variable consideration, we utilize the expected value method under a portfolio approach. Our estimate requires significant judgment and is developed using historical reimbursement data from payors and patients, as well as known current reimbursement trends not reflected in the historical data. As these contracts typically have a single performance obligation, no allocation of the transaction price is required in Step 4 of the model. Control over genetic testing services is transferred to our ordering physicians at a point in time. Specifically, we determined the customer obtains control of the promised service upon our delivery of the test results.

Certain incremental costs pertaining to both clinical insurance and institutional, such as commissions, are incurred in obtaining clinical contracts. Historically contract costs have not been significant to the financial statements. We have elected to utilize the practical expedient to expense incremental costs of obtaining a contract that meet the capitalization criteria, as the amortization period of any contract acquisition asset would be one year or less due to the short-term nature of the customer life.

Significant Judgments and Contract Estimates

Genetic Testing Services

Accounting for clinical insurance contracts includes estimation of the transaction price, defined as the amount we expect to be entitled to receive in exchange for providing the services under the contract. Due to our out-of-network status with the majority of payors, estimation of the transaction price represents variable consideration. In order to estimate variable consideration, we utilize a portfolio approach in which payors with similar reimbursement experience are grouped into portfolios. Our estimates of variable consideration are based primarily on historical reimbursement data. Certain assumptions will also be adjusted based on known and anticipated factors not reflected in the historical reimbursement data. We monitor these accrual estimates at each reporting period based on actual cash collections in order to assess whether a revision to the estimate is required. Both the initial accrual estimate and any subsequent revision to the estimate contain uncertainty and require the use of judgment in the estimation of the transaction price and application of the constraint for variable consideration. If actual results in the future vary from the Company’s estimates, the Company will adjust these estimates, which would affect revenue and earnings in the period such variances become known.

Accounting Pronouncements Recently Adopted

ASU 2014-09

The Company adopted ASU 2014-09 Revenue from Contracts with Customers and all related amendments (collectively codified as ASC 606) on January 1, 2018 utilizing the modified retrospective method, meaning the cumulative effect of applying the standard to all contracts completed as of the date of initial application was recognized to opening retained earnings as of January 1, 2018. Comparative information from prior periods has not been restated and continues to be reported under the accounting standards in effect for those periods.

Financial Statement Impact of Adoption ASC 606

The cumulative effect of changes made to the Condensed Consolidated Balance Sheet at January 1, 2018 for the adoption of ASC 606 were as follows (in thousands):

	Balance at December 31, 2017			Adjustments Due to ASC 606			Balance at January 1, 2018
Condensed Consolidated Balance Sheet data
Assets:
Accounts receivable	$	4,005		$	327		$	4,332
Deferred tax asset / (liability)	$	126		$	(74	)	$	52

Equity:
Accumulated deficit	$	(57,664	)	$	253		$	(57,411	)

In accordance with ASC 606 requirements under the modified retrospective method of adoption, the disclosure of the impacts to condensed consolidated financial statements as of and for the three months ended March 31, 2018 were as follows (in thousands):

	As reported			Adjustments Due to ASC 606				Balances without the adoption of Topic 606
Condensed Consolidated Balance Sheet data
Assets:
Accounts receivable	$	4,969		$	(150	)		$	4,819
Deferred tax asset	$	505		$	74			$	579

Equity:
Accumulated deficit	$	(59,321	)	$	(76	)		$	(59,397	)

Condensed Consolidated Statements of Operations data
Revenue:
Revenue	$	4,653		$	177		*	$	4,830
_______________________________
* Q1 2018 revenue under ASC 605 would have been greater than under ASC 606 because the amount of cash receipts in Q1 2018 from current and prior period insurance billings was greater than the estimated collections for services delivered and billed in Q1 2018.

There was no impact on the condensed consolidated statements of cash flows for the three months ended March 31, 2018.

Disaggregation of Revenue

The Company classifies its customers by payor type, including them in either Clinical Institutional or Clinical Insurance, as we believe this best depicts how the nature, amount, timing, and uncertainty of our revenue and cash flows are affected by economic factors. The following table summarizes revenue from contracts with customers by payor type for the three months ended March 31, 2018.

	Three months ended
	March 31, 2018
Genetic Testing Services by payor
Institutional	$	4,580
Insurance		73
Total Revenue	$	4,653

There was no material variable consideration recognized in the current period that relates to performance obligations that were completed in the prior period.

Transaction Price Allocated to Future Performance Obligations

ASC 606 requires that the Company disclose the aggregate amount of transaction price that is allocated to performance obligations that have not yet been satisfied as March 31, 2018. ASC 606 provides certain practical expedients that limit the requirement to disclose the aggregate amount of transaction price allocated to unsatisfied performance obligations.

The Company applied the practical expedient to not disclose the amount of transaction price allocated to unsatisfied performance obligations when the performance obligation is part of a contract that has an original expected duration of one year or less. The Company does not have material future obligations associated with Genetic Testing Services that extend beyond one year.

ASU No. 2016-01

In January 2016, the FASB issued ASU No. 2016-01, Financial Instruments Overall (Subtopic 825-10): Recognition and Measurement of Financial Assets and Financial Liabilities, which addresses certain aspects of recognition, measurement, presentation, and disclosure of financial instruments, including a provision that requires equity investments (except for investments accounted for under the equity method of accounting) to be measured at fair value, with changes in fair value recognized in current earnings. The ASU is effective for the Company in the first quarter of 2018, with early adoption permitted. The adoption of this update did not have a material impact on our Consolidated Financial Statements.

ASU No. 2016-15

In August 2016, the FASB issued ASU No. 2016-15, Statement of Cash Flows (Topic 230). The standard clarifies the way certain cash receipts and cash payments are classified with the objective of reducing the existing diversity in practice. The standard is effective for fiscal years and interim periods beginning after December 15, 2017. Early adoption is permitted for all periods beginning after December 15, 2016. The adoption of this update did not have a material impact on our Consolidated Financial Statements.

Recent Accounting Pronouncements

We evaluate all Accounting Standards Updates (ASUs) issued by the Financial Accounting Standards Board (FASB) for consideration of their applicability. ASUs not included in our disclosures were assessed and determined to be either not applicable or are not expected to have a material impact on our Consolidated Financial Statements.

ASU No. 2016-02

In February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842). The update is aimed at making leasing activities more transparent and comparable and requires substantially all leases be recognized by lessees on their balance sheet as a right-of-use asset and corresponding lease liability, including leases currently accounted for as operating leases. This guidance will become effective for interim and annual reporting periods beginning with the year ending December 31, 2019. The standard requires the use of a modified retrospective transition approach for existing leases. Early adoption is permitted. The Company is still performing its assessment of ASU 2016-02, however expects that substantially all of its operating lease commitments will be subject to the new guidance.

ASU No. 2016-13

In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments-Credit Losses: Measurement of Credit Losses on Financial Instruments. ASU No. 2016-13 replaces the incurred loss impairment methodology in current U.S. GAAP with a methodology that reflects expected credit losses. The update is intended to provide financial statement users with more decision-useful information about the expected credit losses on financial instruments and other commitments to extend credit held by a reporting entity at each reporting date. Entities will apply the standard’s provisions as a cumulative-effect adjustment to retained earnings as of the beginning of the first reporting period in which the guidance is effective. The standard will be effective for annual reporting periods beginning after December 15, 2019, including interim periods within those reporting periods. Early adoption is permitted. The Company has not yet evaluated the effect this ASU will have on its consolidated financial statements and related disclosures.

ASU No. 2017-08

In March 2017, the FASB issued ASU No. 2017-08, Receivables–Nonrefundable Fees and Other Costs (Subtopic 310-20). Under the ASU, entities must amortize to the earliest call date the premium on certain purchased callable debt securities. The ASU does not require any accounting change for debt securities held at a discount. The guidance calls for a modified retrospective transition approach under which a cumulative-effect adjustment will be made to retained earnings as of the beginning of the first reporting period in which the guidance is adopted. The ASU is effective for public business entities for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2018. Early adoption is permitted for all entities, including in an interim period. The Company has not yet evaluated the effect this ASU will have on its consolidated financial statements and related disclosures.

ASU No. 2018-02

In February 2018, the FASB issued ASU No. 2018-02, Income Statement–Reporting Comprehensive Income (Topic 220): Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income, which allows a reclassification from accumulated other comprehensive income to retained earnings for stranded tax effects resulting from the Tax Cuts and Jobs Act enacted by the U.S. federal government on December 22, 2017 (the “2017 Tax Act”). Consequently, the amendments eliminate the stranded tax effects resulting from the 2017 Tax Act and will improve the usefulness of information reported to financial statement users. The amendments in this ASU are effective for all entities for fiscal years beginning after December 15, 2018, and interim periods within those fiscal years. Early adoption is permitted, including adoption in any interim period, (1) for public business entities for reporting periods for which financial statements have not yet been issued and (2) for all other entities for reporting periods for which financial statements have not yet been made available for issuance. The Company is currently evaluating the effect this ASU will have on its consolidated financial statements and related disclosures.

Marketable Securities

3 Months Ended

Mar. 31, 2018

Investments Debt And Equity Securities [Abstract]

Marketable Securities

Note 3. Marketable Securities

The Company’s marketable securities consisted of the following:

	March 31, 2018
	Amortized Cost Basis		Unrealized Gains		Unrealized Losses			Aggregate Fair Value
	(in thousands)
Marketable securities:
Short-term
Cash equivalents	$	893	$	—	$	—		$	893
Corporate debt securities		23,310		2		(101	)		23,211
Total short-term marketable securities		24,203		2		(101	)		24,104
Corporate debt securities		10,431		—		(146	)		10,285
Total long-term marketable securities		10,431		—		(146	)		10,285
Total marketable securities	$	34,634	$	2	$	(247	)	$	34,389

	December 31, 2017
	Amortized Cost Basis		Unrealized Gains		Unrealized Losses			Aggregate Fair Value
	(in thousands)
Marketable securities:
Short-term
Cash equivalents	$	723	$	—	$	—		$	723
Corporate debt securities		20,040		2		(48	)		19,994
Total short-term marketable securities		20,763		2		(48	)		20,717
Corporate debt securities		14,999		—		(116	)		14,883
Total long-term marketable securities		14,999		—		(116	)		14,883
Total marketable securities	$	35,762	$	2	$	(164	)	$	35,600

Management determined that the gross unrealized losses of $247,000 on the Company’s marketable securities as of March 31, 2018 were temporary in nature. Gross unrealized losses on the Company’s marketable securities were $164,000 as of December 31, 2017. The Company currently does not intend to sell these securities prior to maturity and does not consider these investments to be other-than-temporarily impaired as of March 31, 2018.

Fair Value Measurements

3 Months Ended

Mar. 31, 2018

Fair Value Disclosures [Abstract]

Fair Value Measurements

Note 4. Fair Value Measurements

The authoritative guidance on fair value measurements establishes a framework with respect to measuring assets and liabilities at fair value on a recurring basis and non-recurring basis. Under the framework, fair value is defined as the exit price, or the amount that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants, as of the measurement date. The framework also establishes a three-tier hierarchy for inputs used in measuring fair value that maximizes the use of observable inputs and minimizes the use of unobservable inputs by requiring that the most observable inputs be used when available. Observable inputs are inputs market participants would use in valuing the asset or liability and are developed based on market data obtained from sources independent of our Company. Unobservable inputs are inputs that reflect the Company’s assumptions about the factors market participants would use in valuing the asset or liability and are developed based on the best information available in the circumstances. The hierarchy consists of the following three levels:

Level 1:

Inputs are quoted prices (unadjusted) in active markets for identical assets or liabilities that the

reporting entity can access at the measurement date.

Level 2:

Inputs are inputs other than quoted prices included within Level 1 that are observable for the

asset or liability, either directly or indirectly.

Level 3:

Inputs are unobservable inputs for the asset or liability.

The following table presents information about our financial assets measured at fair value on a recurring basis, based on the three-tier fair value hierarchy:

	March 31, 2018
	Total		Level 1		Level 2		Level 3
	(in thousands)
Marketable securities:
Cash equivalents:
Money market funds	$	94	$	94	$	—	$	—
Corporate debt securities		799		—		799		—
Marketable securities:
Corporate debt securities		33,496		—		33,496		—
Total marketable securities	$	34,389	$	94	$	34,295	$	—

	December 31, 2017
	Total		Level 1		Level 2		Level 3
	(in thousands)
Marketable securities:
Cash equivalents	$	723	$	723	$	—	$	—
Corporate debt securities		34,877		—		34,877		—
Total marketable securities	$	35,600	$	723	$	34,877	$	—

The Company’s Level 1 assets include money market instruments and are valued based upon observable market prices. Level 2 assets consist of marketable investment securities consisting of corporate bonds. Level 2 securities are valued based upon observable inputs that include reported trades, broker/dealer quotes, bids and offers. As of March 31, 2018, the Company had no investments that were measured using unobservable (Level 3) inputs.

There were no transfers between fair value measurement levels during the three months ended March 31, 2018.

Gross unrealized gains or losses for cash equivalents and marketable securities as of March 31, 2018 were not material. As of March 31, 2018, unrealized losses for securities in an unrealized loss position for more than 12 months were $198,000. During the three months ending March 31, 2018 the Company did not recognize other-than-temporary impairment losses related to its marketable securities.

Fixed Assets

3 Months Ended

Mar. 31, 2018

Property Plant And Equipment [Abstract]

Fixed Assets

Note 5. Fixed Assets

Major classes of fixed assets consisted of the following:

		March 31,			December 31,
	Useful Lives	2018			2017
		(in thousands)
Computer hardware	3 Years	$	1,500		$	1,435
Computer software	3 Years		468			463
Medical lab equipment	5 Years		8,136			7,145
Furniture and fixtures	5 Years		199			159
Leasehold improvements	Shorter of lease term or estimated useful life		803			763
Assets not yet placed in service			31			1,074
Total			11,137			11,039
Less: Accumulated depreciation			(4,284	)		(3,767	)
Property and equipment, net		$	6,853		$	7,272

Depreciation expense on fixed assets totaled $516,000 and $412,000 for the first quarters of 2018 and 2017, respectively.

Other Current Assets

3 Months Ended

Mar. 31, 2018

Deferred Costs Capitalized Prepaid And Other Assets Disclosure [Abstract]

Other Current Assets

Note 6. Other Current Assets

Other current assets consisted of the following:

	March 31,		December 31,
	2018		2017
	(in thousands)
Reagents	$	398	$	231
Prepaid expenses		635		624
Prepaid income taxes		1,313		1,313
Marketable securities interest receivable		239		204
Other receivable		36		66
Total	$	2,621	$	2,438

Reagents are used for DNA sequencing applications in the Company’s DNA sequencing equipment.

Reporting Segment and Geographic Information

3 Months Ended

Mar. 31, 2018

Segment Reporting [Abstract]

Reporting Segment and Geographic Information

Note 7. Reporting Segment and Geographic Information

The Company views its operations and manages its business in one reporting segment. All long-lived assets were located in the United States during the first quarters of 2018 and 2017. Revenue by region was as follows:

	Three Months Ended March 31,
	2018		2017
	(in thousands)
Revenue:
United States	$	2,527	$	2,090
Foreign:
Canada		970		1,083
People's Republic of China ("PRC")		24		1,525
Other Countries		1,132		608
Total	$	4,653	$	5,306

Commitments and Contingencies	3 Months Ended
Commitments and Contingencies	Mar. 31, 2018
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	Note 8. Commitments and Contingencies Operating Leases The Company has commitments under various non-cancelable operating leases with varying terms through January 2023. The Company has options to renew some of these leases for three years after their expiration. The Company’s headquarters is located in Temple City, California, which is comprised of various corporate offices and a laboratory certified under the Clinical Laboratory Improvement Amendments of 1988 (“CLIA”), accredited by the College of American Pathologists (“CAP”) and licensed by the State of California Department of Public Health (“CA DPH”). Additional offices are located in El Monte, California and Atlanta, Georgia and are used for certain research and development, customer service, report generation and other administrative functions. Rent expense was approximately $109,000 and $53,000 for the first quarters of 2018 and 2017, respectively. On January 31, 2018, we entered into a lease renewal of our headquarters in Temple City, California, which commenced on February 1, 2018 and expires January 31, 2021. The total annual rent under the lease is approximately $269,000. FF Gene Biotech See Note 14 for a description of the Company’s commitments related to its joint venture, FF Gene Biotech (as defined in Note 14). Purchase Obligations As of March 31, 2018, the Company had purchase obligations of $2.3 million for reagents and equipment. Contingencies From time to time, the Company may be subject to legal proceedings and claims arising in the ordinary course of business. Management does not believe that the outcome of any of these matters will have a material effect on the Company’s consolidated financial position, results of operations or cash flows.

Stockholders' Equity	3 Months Ended
Stockholders' Equity	Mar. 31, 2018
Equity [Abstract]
Stockholders' Equity	Note 9. Stockholders’ Equity Components of Comprehensive Income (Loss) Comprehensive income (loss) consists of two components: net income (loss), and other comprehensive income (loss) (“OCI”). OCI refers to revenue, expenses, gains and losses that, in conformity with U.S. GAAP, are recorded as in the Company’s consolidated statements of stockholders’ equity but are excluded from the Company’s consolidated statements of operations, and as a result, its net income (loss). The Company’s OCI consists of foreign currency translation adjustments from its subsidiaries not using the U.S. dollar as their functional currency and unrealized gains and losses on marketable securities classified as available-for-sale, net of taxes. The tax effects related to unrealized holding gains (losses) on marketable securities were $55,000 and $48,000 for the first quarters of 2018 and 2017, respectively.

Equity-Based Compensation

3 Months Ended

Mar. 31, 2018

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Equity-Based Compensation

Note 10. Equity-Based Compensation

Equity-based compensation expense for awards granted to employees is measured based on the fair value of the award on the grant date and recognized in the Company’s consolidated statements of operations over the period during which the employee is required to perform services in exchange for the award (generally, the vesting period of the award). Compensation expense for awards with both a service and performance condition is recognized over the period required to achieve both conditions using the accelerated attribution method. The Company estimates the fair value of stock options using the Black-Scholes option valuation model. The Company measures the fair value of RSUs and share awards based on the fair value of the underlying shares on the date of grant. For awards of Fulgent LLC profits interests that were granted before the Reorganization, the fair value was measured using the Black-Scholes option valuation model.

The Company has included equity-based compensation expense as part of cost of revenue and operating expenses in the accompanying condensed consolidated statements of operations as follows:

	Three Months Ended March 31,
	2018		2017
	(in thousands)
Cost of revenue	$	124	$	146
Research and development		132		211
Selling and marketing		108		69
General and administrative		181		139
Total	$	545	$	565

Award Activity

The below discussions of equity-based award activity, including all share numbers and weighted-average exercise prices, have been adjusted to give retroactive effect to the Reorganization as if it occurred at the beginning of each period presented.

Option Awards

The following table summarizes activity for options to acquire shares of the Company’s common stock in the three months ended March 31, 2018:

	Number of Shares Subject to Options (in thousands)			Weighted- Average Exercise Price		Weighted- Average Remaining Contractual Life (in years)		Aggregate Intrinsic Value (in thousands) (1)
Balance at December 31, 2017		465		$	0.84		8.0	$	1,785
Authorized		—
Granted		—
Exercised		(5	)	$	0.38				17
Canceled		(5	)	$	2.37
Balance at March 31, 2018		455		$	0.82		7.8	$	1,584
Exercisable as of March 31, 2018		230		$	0.77		7.7	$	804
(1) Aggregate intrinsic value is calculated as the difference between (i) the exercise price of options that, as of the applicable date, have an exercise price in excess of the fair value of the Company’s common stock, and (ii) the fair value of the Company’s common stock as of the applicable date.

The Company granted no option awards in the three months ended March 31, 2018. The total fair value of options that vested during the three months ended March 31, 2018 was $163,000. As of March 31, 2018, the remaining unrecognized compensation expense of $374,000 related to outstanding stock options is expected to be recognized over a weighted-average period of 1.6 years.

RSU Awards

RSUs are awards that entitle the holder to receive shares of the Company’s common stock upon satisfaction of vesting conditions. Each RSU represents the contingent right to receive one share of the Company’s common stock upon vesting and settlement.

The following table summarizes activity for RSUs relating to shares of the Company’s common stock in the three months ended March 31, 2018:

	Number of Shares (in thousands)			Weighted-Average Grant-Date Fair Value
Balance at December 31, 2017		937		$	7.39
Granted		175		$	4.70
Vested and settled		(24	)	$	9.69
Forfeited		(20	)	$	8.56
Balance at March 31, 2018		1,068		$	6.88

The RSU awards granted in the three months ended March 31, 2018 will result in aggregate equity-based compensation expense of $818,000, in each case to be recognized over four years from the grant date of each award granted in the period. As of March 31, 2018, the remaining unrecognized compensation expense of $6.3 million related to outstanding RSUs is expected to be recognized over a weighted-average period of 3.3 years.

Income Taxes	3 Months Ended
Income Taxes	Mar. 31, 2018
Income Tax Disclosure [Abstract]
Income Taxes	Note 11. Income Taxes Provision for income taxes consists of U.S. federal and state income taxes. A deferred tax liability is recognized for all taxable temporary differences, and a deferred tax asset is recognized for all deductible temporary differences, operating losses and tax credit carryforwards. A valuation allowance is provided when it is more likely than not that some portion or all of a deferred tax asset will not be realized. The 2017 Tax Act, which was signed into law on December 22, 2017, has resulted in significant changes to the U.S. corporate income tax system. These changes include, among others, a federal statutory rate reduction from 35% to 21%, the elimination or reduction of certain domestic deductions and credits and limitations on the deductibility of interest expenses and executive compensation expenses. The 2017 Tax Act also transitions international taxation from a worldwide system to a modified territorial system and includes base erosion prevention measures on non-U.S. earnings. These changes are effective beginning in 2018. The Company accounts for changes in tax rates and tax laws in the period of enactment. On December 22, 2017, SEC Staff Accounting Bulletin No. 118, Income Tax Accounting Implications of the Tax Cuts and Jobs Act ("SAB 118"), was issued to address the application of generally accepted accounting principles in the United States of America in situations when a registrant does not have the necessary information available, prepared, or analyzed (including computations) in reasonable detail to complete the accounting for certain income tax effects of the 2017 Act. In accordance with SAB 118, for 2017, due to the reduction in the corporate income tax rate with the enactment of the 2017 Tax Act, the Company recorded a tax expense of $22,000 related to the revaluation of its net deferred tax assets. The Company has determined that the various other provisions of the 2017 Tax Act are not expected to have a material impact on the Company’s results of operations or financial condition, largely because of the amount of the Company’s net operating loss carryover and the Company has no unrepatriated foreign earnings. In order to determine the Company’s quarterly provision for income taxes, the Company used an estimated annual effective tax rate for the full fiscal year ending December 31, 2018, which is based on expected annual income and statutory tax rates in the various jurisdictions in which the Company operates, adjusted for discrete items recognized during the period. Certain significant or unusual items are separately recognized in the quarter during which they occur and can cause the effective tax rate to vary from quarter to quarter. The Company's effective income tax rate was 21% and 31% for the three months ended March 31, 2018 and 2017. The effective rate for March 31, 2018 includes the reduction in the U.S. federal corporate rate from 35% to 21% for tax years beginning after December 31, 2017. The difference in the effective tax rate from the statutory tax rate was primarily attributable to the net effect of state income taxes and certain expenses or adjustments related to equity-based compensation. The Company will file income tax returns in the U.S. federal jurisdiction, and various states and foreign jurisdictions for the year ending December 31, 2018. As of March 31, 2018, there were no pending tax audits in any jurisdiction.

Income (Loss) Per Share

3 Months Ended

Mar. 31, 2018

Earnings Per Share [Abstract]

Income (Loss) per Share

Note 12. Income (Loss) per Share

The following table presents the calculation of basic and diluted income (loss) per share for the three months ended March 31, 2018 and 2017:

	Three Months Ended March 31,
	2018			2017
	(in thousands, except per share data)
Net income (loss)	$	(1,910	)	$	232
Weighted-average common shares—outstanding, basic		17,864			17,676
Weighted-average common shares—outstanding, diluted		17,864			18,178
Net income (loss) per common share, basic	$	(0.11	)	$	0.01
Net income (loss) per common share, diluted	$	(0.11	)	$	0.01

The following securities have been excluded from the calculation of diluted income (loss) per share because their effect would have been anti-dilutive:

	Three Months Ended March 31,
	2018		2017
	(in thousands)
Options		454		22
RSUs		955		—

The anti-dilutive shares described above were calculated using the treasury stock method. During the three months ended March 31, 2018, the Company had outstanding stock options and RSUs that were excluded from the weighted-average share calculation due to the Company’s net loss position.

Related Party	3 Months Ended
Related Party	Mar. 31, 2018
Related Party Transactions [Abstract]
Related Party	Note 13. Related Party Dr. Yun Yen, who is a member of the Company’s Board of Directors and a stockholder, serves as the President and Chairman of the Board for the Sino-American Cancer Foundation (the “Foundation”) and served as the President for the Taipei Medical University (the “University”), from August 1, 2011 through July 31, 2016 and currently serves as a Chair Professor for the University. From time to time, the Company performs research testing services for the Foundation. The Company did not recognize any revenue during the three months ended March 31, 2018 or 2017 as consideration for such services. Additionally, the Company subleases certain of its headquarters facilities to the Foundation. The Company recognized $8,000 and zero in the three months ended March 31, 2018 and 2017, respectively, as consideration for such sublease. As of March 31, 2018, and December 31, 2017, zero was owed to the Company by the Foundation in connection with these relationships. From time to time, the Company performs genetic sequencing services for the University. The Company recognized $9,000 and $12,000 as consideration for such services in the three months ended March 31, 2018 and 2017, respectively. As of March 31, 2018, and December 31, 2017, $33,000 and $40,000, respectively, was owed to the Company by the University in connection with this relationship. As more fully described in Note 14, in April 2017, the Company, through an affiliated company formed for the purpose of the relationship, entered into a cooperation agreement (the “JV Agreement”) with Xilong Scientific Co., Ltd. (“Xilong Scientific”) and Fuzhou Jinqiang Investment Partnership (LP) (“FJIP”) to form a joint venture under the laws of the People’s Republic of China (“PRC”) called Fujian Fujun Gene Biotech Co., Ltd. (“FF Gene Biotech”). Xilong Scientific is an affiliate of Xi Long USA, Inc., a large stockholder of the Company that, as of March 31, 2018, owned 11% of the outstanding shares of the Company’s common stock, and FJIP is owned by key management of FF Gene Biotech, including Dr. Han Lin Gao, the Chief Scientific Officer and a large stockholder of the Company and the owner of approximately 25% of FJIP. Fulgent Pharma utilizes space in the facility at which our laboratory and corporate headquarters are located. Since the completion of the Pharma Split-Off, Fulgent Pharma reimburses us for the portion of the rent we pay that is attributable to the space it uses, which amounts are not significant. As of March 31, 2018, and December 31, 2017, $9,000 and $3,000, respectively, was due from Fulgent Pharma as a result of this arrangement, which is recorded in Other receivable in Other current assets in the accompanying condensed consolidated balance sheets.

Equity Method Investments

3 Months Ended

Mar. 31, 2018

Equity Method Investments And Joint Ventures [Abstract]

Equity Method Investments

Note 14. Equity Method Investments

In April 2017, the Company, through an affiliated company formed for the purpose of the relationship, entered into the JV Agreement with Xilong Scientific and FJIP to form FF Gene Biotech, a joint venture formed under the laws of the PRC to offer genetic testing services to customers in the PRC. Pursuant to the terms of the JV Agreement, the Company has agreed to contribute to FF Gene Biotech genetic sequencing and other equipment with a total cost of 60,000,000 renminbi (“RMB”) over a three-year period for a 30% ownership interest in FF Gene Biotech, Xilong Scientific has agreed to contribute to FF Gene Biotech 102,000,000 RMB over a three-year period for a 51% ownership interest in the FF Gene Biotech, and FJIP has agreed to contribute to FF Gene Biotech 19,000,000 RMB over a five-year period for a 19% ownership interest in FF Gene Biotech. The Company’s maximum exposure to fund losses of FF Gene Biotech as a result of its minority ownership of this entity is equal to its contribution obligation under the JV Agreement as described above. As of March 31, 2018, 43,600,000 RMB (or approximately $6.9 million U.S. dollars) remains to be contributed to the investee under the terms of the JV agreement. The Company has purchased and contributed equipment with an aggregate fair value of $2.5 million pursuant to its contribution commitment under the JV Agreement, all of which was contributed in 2017. The Company accounted for this contribution in accordance with ASC 845, Nonmonetary Transactions, and recorded an investment based on the fair value of the contributed equipment, which is the same as carryover basis.

The Company concluded FF Gene Biotech is a variable interest entity as FF Gene Biotech lacks sufficient capital to operate independently. The Company concluded that it alone does not have the power to direct the most significant activities of FF Gene Biotech and therefore is not the primary beneficiary of the entity. Judgment regarding the level of influence over FF Gene Biotech includes consideration of key factors such as the Company's ownership interest, representation on the board of directors or other management body and participation in policy-making decisions.

The Company accounts for its 30% interest in FF Gene Biotech using the equity method of accounting. The Company recorded its proportionate share of the losses of FF Gene Biotech in the first quarter of 2018 in the accompanying condensed consolidated statements of operations, and recorded its contribution to date, net of its proportionate share in the accumulated losses of FF Gene Biotech, in the accompanying condensed consolidated balance sheet as of March 31, 2018.

The Company entered into a license agreement with FF Gene Biotech, pursuant to which it granted FF Gene Biotech a license to use certain of the Company’s clinical molecular diagnostic gene detection technology and related software and proprietary reference library of genetic information, along with any improvements on this technology that they may develop during the term of the license agreement. Under the license agreement, FF Gene Biotech will pay to the Company, on a quarterly basis, certain royalties based on the revenues of FF Gene Biotech. The Company earned $18,000 for royalties under the license agreement for the first quarter of 2018.

In November 2017, FF Gene Biotech invested and formed a majority-owned subsidiary that focuses on sales and marketing for FF Gene Biotech.

Equity method investments as of March 31, 2018 and December 31, 2017 consisted of the following:

	March 31, 2018					December 31, 2017
	Carrying Value		Ownership Percentage			Carrying Value		Ownership Percentage
	(in thousands)					(in thousands)
FF Gene Biotech	$	1,692		30	%	$	1,937		30	%
Total equity method investments	$	1,692		30	%	$	1,937		30	%

Summary of Significant Accounting Policies (Policies)

3 Months Ended

Mar. 31, 2018

Accounting Policies [Abstract]

Use of Estimates

Foreign Currency Translation and Foreign Currency Transactions

Concentration of Customers

Revenue Recognition

Performance Obligations

Genetic Testing Services

Clinical – Institutional

Clinical – Insurance

Significant Judgments and Contract Estimates

Genetic Testing Services

Accounting Pronouncements Recently Adopted and Recent Accounting Pronouncements

Accounting Pronouncements Recently Adopted

ASU 2014-09

Financial Statement Impact of Adoption ASC 606

The cumulative effect of changes made to the Condensed Consolidated Balance Sheet at January 1, 2018 for the adoption of ASC 606 were as follows (in thousands):

	Balance at December 31, 2017			Adjustments Due to ASC 606			Balance at January 1, 2018
Condensed Consolidated Balance Sheet data
Assets:
Accounts receivable	$	4,005		$	327		$	4,332
Deferred tax asset / (liability)	$	126		$	(74	)	$	52

Equity:
Accumulated deficit	$	(57,664	)	$	253		$	(57,411	)

	As reported			Adjustments Due to ASC 606				Balances without the adoption of Topic 606
Condensed Consolidated Balance Sheet data
Assets:
Accounts receivable	$	4,969		$	(150	)		$	4,819
Deferred tax asset	$	505		$	74			$	579

Equity:
Accumulated deficit	$	(59,321	)	$	(76	)		$	(59,397	)

Condensed Consolidated Statements of Operations data
Revenue:
Revenue	$	4,653		$	177		*	$	4,830
_______________________________
* Q1 2018 revenue under ASC 605 would have been greater than under ASC 606 because the amount of cash receipts in Q1 2018 from current and prior period insurance billings was greater than the estimated collections for services delivered and billed in Q1 2018.

There was no impact on the condensed consolidated statements of cash flows for the three months ended March 31, 2018.

Disaggregation of Revenue

	Three months ended
	March 31, 2018
Genetic Testing Services by payor
Institutional	$	4,580
Insurance		73
Total Revenue	$	4,653

There was no material variable consideration recognized in the current period that relates to performance obligations that were completed in the prior period.

Transaction Price Allocated to Future Performance Obligations

ASU No. 2016-01

ASU No. 2016-15

Recent Accounting Pronouncements

ASU No. 2016-02

ASU No. 2016-13

ASU No. 2017-08

ASU No. 2018-02

Summary of Significant Accounting Policies (Tables) - Accounting Standards Update 2014-09

3 Months Ended

Mar. 31, 2018

Summary of Impact on Financial Statement

The cumulative effect of changes made to the Condensed Consolidated Balance Sheet at January 1, 2018 for the adoption of ASC 606 were as follows (in thousands):

	Balance at December 31, 2017			Adjustments Due to ASC 606			Balance at January 1, 2018
Condensed Consolidated Balance Sheet data
Assets:
Accounts receivable	$	4,005		$	327		$	4,332
Deferred tax asset / (liability)	$	126		$	(74	)	$	52

Equity:
Accumulated deficit	$	(57,664	)	$	253		$	(57,411	)

	As reported			Adjustments Due to ASC 606				Balances without the adoption of Topic 606
Condensed Consolidated Balance Sheet data
Assets:
Accounts receivable	$	4,969		$	(150	)		$	4,819
Deferred tax asset	$	505		$	74			$	579

Equity:
Accumulated deficit	$	(59,321	)	$	(76	)		$	(59,397	)

Condensed Consolidated Statements of Operations data
Revenue:
Revenue	$	4,653		$	177		*	$	4,830
_______________________________
* Q1 2018 revenue under ASC 605 would have been greater than under ASC 606 because the amount of cash receipts in Q1 2018 from current and prior period insurance billings was greater than the estimated collections for services delivered and billed in Q1 2018.

Summary of Revenue from Contracts with Customers by Payor Type

The following table summarizes revenue from contracts with customers by payor type for the three months ended March 31, 2018.

	Three months ended
	March 31, 2018
Genetic Testing Services by payor
Institutional	$	4,580
Insurance		73
Total Revenue	$	4,653

Marketable Securities (Tables)

3 Months Ended

Mar. 31, 2018

Investments Debt And Equity Securities [Abstract]

Summary of Marketable Securities

The Company’s marketable securities consisted of the following:

	March 31, 2018
	Amortized Cost Basis		Unrealized Gains		Unrealized Losses			Aggregate Fair Value
	(in thousands)
Marketable securities:
Short-term
Cash equivalents	$	893	$	—	$	—		$	893
Corporate debt securities		23,310		2		(101	)		23,211
Total short-term marketable securities		24,203		2		(101	)		24,104
Corporate debt securities		10,431		—		(146	)		10,285
Total long-term marketable securities		10,431		—		(146	)		10,285
Total marketable securities	$	34,634	$	2	$	(247	)	$	34,389

	December 31, 2017
	Amortized Cost Basis		Unrealized Gains		Unrealized Losses			Aggregate Fair Value
	(in thousands)
Marketable securities:
Short-term
Cash equivalents	$	723	$	—	$	—		$	723
Corporate debt securities		20,040		2		(48	)		19,994
Total short-term marketable securities		20,763		2		(48	)		20,717
Corporate debt securities		14,999		—		(116	)		14,883
Total long-term marketable securities		14,999		—		(116	)		14,883
Total marketable securities	$	35,762	$	2	$	(164	)	$	35,600

Fair Value Measurements (Tables)

3 Months Ended

Mar. 31, 2018

Fair Value Disclosures [Abstract]

Information about Financial Assets Measured at Fair Value on Recurring Basis Based on Three-Tier Fair Value Hierarchy

The following table presents information about our financial assets measured at fair value on a recurring basis, based on the three-tier fair value hierarchy:

	March 31, 2018
	Total		Level 1		Level 2		Level 3
	(in thousands)
Marketable securities:
Cash equivalents:
Money market funds	$	94	$	94	$	—	$	—
Corporate debt securities		799		—		799		—
Marketable securities:
Corporate debt securities		33,496		—		33,496		—
Total marketable securities	$	34,389	$	94	$	34,295	$	—

	December 31, 2017
	Total		Level 1		Level 2		Level 3
	(in thousands)
Marketable securities:
Cash equivalents	$	723	$	723	$	—	$	—
Corporate debt securities		34,877		—		34,877		—
Total marketable securities	$	35,600	$	723	$	34,877	$	—

Fixed Assets (Tables)

3 Months Ended

Mar. 31, 2018

Property Plant And Equipment [Abstract]

Major Classes of Fixed Assets

Major classes of fixed assets consisted of the following:

		March 31,			December 31,
	Useful Lives	2018			2017
		(in thousands)
Computer hardware	3 Years	$	1,500		$	1,435
Computer software	3 Years		468			463
Medical lab equipment	5 Years		8,136			7,145
Furniture and fixtures	5 Years		199			159
Leasehold improvements	Shorter of lease term or estimated useful life		803			763
Assets not yet placed in service			31			1,074
Total			11,137			11,039
Less: Accumulated depreciation			(4,284	)		(3,767	)
Property and equipment, net		$	6,853		$	7,272

Other Current Assets (Tables)

3 Months Ended

Mar. 31, 2018

Deferred Costs Capitalized Prepaid And Other Assets Disclosure [Abstract]

Schedule of Other Current Assets

Other current assets consisted of the following:

	March 31,		December 31,
	2018		2017
	(in thousands)
Reagents	$	398	$	231
Prepaid expenses		635		624
Prepaid income taxes		1,313		1,313
Marketable securities interest receivable		239		204
Other receivable		36		66
Total	$	2,621	$	2,438

Reporting Segment and Geographic Information (Tables)

3 Months Ended

Mar. 31, 2018

Segment Reporting [Abstract]

Summary of Revenue by Geographic Region

Revenue by region was as follows:

	Three Months Ended March 31,
	2018		2017
	(in thousands)
Revenue:
United States	$	2,527	$	2,090
Foreign:
Canada		970		1,083
People's Republic of China ("PRC")		24		1,525
Other Countries		1,132		608
Total	$	4,653	$	5,306

Equity-Based Compensation (Tables)

3 Months Ended

Mar. 31, 2018

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Summary of Equity-Based Compensation

The Company has included equity-based compensation expense as part of cost of revenue and operating expenses in the accompanying condensed consolidated statements of operations as follows:

	Three Months Ended March 31,
	2018		2017
	(in thousands)
Cost of revenue	$	124	$	146
Research and development		132		211
Selling and marketing		108		69
General and administrative		181		139
Total	$	545	$	565

Summary of Activity for Options to Acquire Common Shares

The following table summarizes activity for options to acquire shares of the Company’s common stock in the three months ended March 31, 2018:

	Number of Shares Subject to Options (in thousands)			Weighted- Average Exercise Price		Weighted- Average Remaining Contractual Life (in years)		Aggregate Intrinsic Value (in thousands) (1)
Balance at December 31, 2017		465		$	0.84		8.0	$	1,785
Authorized		—
Granted		—
Exercised		(5	)	$	0.38				17
Canceled		(5	)	$	2.37
Balance at March 31, 2018		455		$	0.82		7.8	$	1,584
Exercisable as of March 31, 2018		230		$	0.77		7.7	$	804
(1) Aggregate intrinsic value is calculated as the difference between (i) the exercise price of options that, as of the applicable date, have an exercise price in excess of the fair value of the Company’s common stock, and (ii) the fair value of the Company’s common stock as of the applicable date.

Summary of Activity for RSUs Relating to Shares of Company's Common Stock

The following table summarizes activity for RSUs relating to shares of the Company’s common stock in the three months ended March 31, 2018:

	Number of Shares (in thousands)			Weighted-Average Grant-Date Fair Value
Balance at December 31, 2017		937		$	7.39
Granted		175		$	4.70
Vested and settled		(24	)	$	9.69
Forfeited		(20	)	$	8.56
Balance at March 31, 2018		1,068		$	6.88

Income (Loss) Per Share (Tables)

3 Months Ended

Mar. 31, 2018

Earnings Per Share [Abstract]

Reconciliation of the Basic and Diluted Income (Loss) Per Share Computations

The following table presents the calculation of basic and diluted income (loss) per share for the three months ended March 31, 2018 and 2017:

	Three Months Ended March 31,
	2018			2017
	(in thousands, except per share data)
Net income (loss)	$	(1,910	)	$	232
Weighted-average common shares—outstanding, basic		17,864			17,676
Weighted-average common shares—outstanding, diluted		17,864			18,178
Net income (loss) per common share, basic	$	(0.11	)	$	0.01
Net income (loss) per common share, diluted	$	(0.11	)	$	0.01

Anti-dilutive Securities Excluded from Calculation of Diluted Income (Loss) Per Share

The following securities have been excluded from the calculation of diluted income (loss) per share because their effect would have been anti-dilutive:

	Three Months Ended March 31,
	2018		2017
	(in thousands)
Options		454		22
RSUs		955		—

Equity Method Investments (Tables)

3 Months Ended

Mar. 31, 2018

Equity Method Investments And Joint Ventures [Abstract]

Schedule of Equity Method Investments

Equity method investments as of March 31, 2018 and December 31, 2017 consisted of the following:

	March 31, 2018					December 31, 2017
	Carrying Value		Ownership Percentage			Carrying Value		Ownership Percentage
	(in thousands)					(in thousands)
FF Gene Biotech	$	1,692		30	%	$	1,937		30	%
Total equity method investments	$	1,692		30	%	$	1,937		30	%

Overview and Basis of Presentation - Additional Information (Details) - USD ($)	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Description Of Business And Basis Of Presentation [Line Items]
Payment of initial public offering costs		$ 801,000
Net cash (used in) provided by operations	$ (1,291,000)	1,508,000
Net cash provided by (used in) financing activities	$ 2,000	(801,000)
Previoulsy Reported
Description Of Business And Basis Of Presentation [Line Items]
Net cash (used in) provided by operations		707,000
Net cash provided by (used in) financing activities		$ 0

Summary of Significant Accounting Policies - Additional Information (Detail)	3 Months Ended
	Mar. 31, 2018 USD ($) Customer	Mar. 31, 2017 Customer	Jan. 01, 2018 USD ($)
Summary Of Significant Accounting Policies [Line Items]
Foreign currency translation gain (loss)	$ 22,000
Adjustment to accumulated deficit and deferred taxes			$ 74,000
Practical expedient not to disclose amount of transaction price allocated to unsatisfied performance obligations	true
Accounting Standards Update 2014-09
Summary Of Significant Accounting Policies [Line Items]
Change in accounting principle, adjustment to accumulated deficit and accounts receivable			$ 327,000
Revenue \| Customer Concentration Risk
Summary Of Significant Accounting Policies [Line Items]
Number of customers \| Customer	1	4
Revenue \| Customer Concentration Risk \| Customer One
Summary Of Significant Accounting Policies [Line Items]
Concentration risk, percentage	13.00%	15.00%
Revenue \| Customer Concentration Risk \| Customer Two
Summary Of Significant Accounting Policies [Line Items]
Concentration risk, percentage		14.00%
Revenue \| Customer Concentration Risk \| Customer Three
Summary Of Significant Accounting Policies [Line Items]
Concentration risk, percentage		11.00%
Revenue \| Customer Concentration Risk \| Customer Four
Summary Of Significant Accounting Policies [Line Items]
Concentration risk, percentage		10.00%

Summary of Significant Accounting Policies -Summary of Cumulative Effect of Changes Made to the Condensed Consolidated Balance Sheet (Detail) - USD ($) $ in Thousands	Mar. 31, 2018	Jan. 01, 2018	Dec. 31, 2017
Assets
Accounts receivable	$ 4,969		$ 4,005
Deferred tax asset / (liability)	505		126
Equity:
Accumulated deficit	(59,321)		$ (57,664)
Accounting Standards Update 2014-09
Assets
Accounts receivable		$ 4,332
Deferred tax asset / (liability)		52
Equity:
Accumulated deficit		(57,411)
Accounting Standards Update 2014-09 \| Adjustments due to ASC 606
Assets
Accounts receivable	(150)	327
Deferred tax asset / (liability)	74	(74)
Equity:
Accumulated deficit	$ (76)	$ 253

Summary of Significant Accounting Policies -Summary of Disclosure of the Impacts to Condensed Consolidated Financial Statements (Detail) - USD ($)
$ in Thousands

3 Months Ended

Mar. 31, 2018

Mar. 31, 2017

Jan. 01, 2018

Dec. 31, 2017

Assets

Accounts receivable

$ 4,969

$ 4,005

Deferred tax asset

505

126

Equity:

Accumulated deficit

(59,321)

$ (57,664)

Revenue:

Revenue

4,653

$ 5,306

Accounting Standards Update 2014-09

Assets

Accounts receivable

$ 4,332

Deferred tax asset

Equity:

Accumulated deficit

(57,411)

Accounting Standards Update 2014-09 | Adjustments due to ASC 606

Assets

Accounts receivable

(150)

327

Deferred tax asset

(74)

Equity:

Accumulated deficit

(76)

$ 253

Revenue:

Revenue

^[1]

177

Accounting Standards Update 2014-09 | Balances without the Adoption of Topic 606

Assets

Accounts receivable

4,819

Deferred tax asset

579

Equity:

Accumulated deficit

(59,397)

Revenue:

Revenue

$ 4,830

[1]	Q1 2018 revenue under ASC 605 would have been greater than under ASC 606 because the amount of cash receipts in Q1 2018 from current and prior period insurance billings was greater than the estimated collections for services delivered and billed in Q1 2018.

Summary of Significant Accounting Policies - Summary of Revenue from Contracts with Customers by Payor Type (Detail) - Accounting Standards Update 2014-09 $ in Thousands	3 Months Ended
	Mar. 31, 2018 USD ($)
Disaggregation Of Revenue [Line Items]
Revenue from contracts with customers by payor type	$ 4,653
Genetic Testing Services \| Institutional
Disaggregation Of Revenue [Line Items]
Revenue from contracts with customers by payor type	4,580
Genetic Testing Services \| Insurance
Disaggregation Of Revenue [Line Items]
Revenue from contracts with customers by payor type	$ 73

Marketable Securities - Summary of Marketable Securities (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Schedule of Available For Sale Securities [Line Items]
Marketable securities, Amortized Cost Basis	$ 34,634	$ 35,762
Marketable securities, Unrealized Gains	2	2
Marketable securities, Unrealized Loses	(247)	(164)
Marketable securities, Aggregate Fair Value	34,389	35,600
Short-Term Marketable Securities
Schedule of Available For Sale Securities [Line Items]
Marketable securities, Amortized Cost Basis	24,203	20,763
Marketable securities, Unrealized Gains	2	2
Marketable securities, Unrealized Loses	(101)	(48)
Marketable securities, Aggregate Fair Value	24,104	20,717
Short-Term Marketable Securities \| Cash Equivalents
Schedule of Available For Sale Securities [Line Items]
Marketable securities, Amortized Cost Basis	893	723
Marketable securities, Aggregate Fair Value	893	723
Short-Term Marketable Securities \| Corporate Debt Securities
Schedule of Available For Sale Securities [Line Items]
Marketable securities, Amortized Cost Basis	23,310	20,040
Marketable securities, Unrealized Gains	2	2
Marketable securities, Unrealized Loses	(101)	(48)
Marketable securities, Aggregate Fair Value	23,211	19,994
Long-Term Marketable Securities
Schedule of Available For Sale Securities [Line Items]
Marketable securities, Amortized Cost Basis	10,431	14,999
Marketable securities, Unrealized Loses	(146)	(116)
Marketable securities, Aggregate Fair Value	10,285	14,883
Long-Term Marketable Securities \| Corporate Debt Securities
Schedule of Available For Sale Securities [Line Items]
Marketable securities, Amortized Cost Basis	10,431	14,999
Marketable securities, Unrealized Loses	(146)	(116)
Marketable securities, Aggregate Fair Value	$ 10,285	$ 14,883

Marketable Securities - Additional Information (Details) - USD ($)	3 Months Ended	12 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Investments Debt And Equity Securities [Abstract]
Gross unrealized loss	$ 247,000	$ 164,000

Fair Value Measurements - Information about Financial Assets Measured at Fair Value on Recurring Basis Based on Three-Tier Fair Value Hierarchy (Details) - Fair Value Measurements Recurring - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total marketable securities	$ 34,389	$ 35,600
Corporate Debt Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total marketable securities	33,496	34,877
Cash Equivalents
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total marketable securities		723
Cash Equivalents \| Corporate Debt Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total marketable securities	799
Cash Equivalents \| Money market funds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total marketable securities	94
Level 1
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total marketable securities	94	723
Level 1 \| Cash Equivalents
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total marketable securities		723
Level 1 \| Cash Equivalents \| Money market funds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total marketable securities	94
Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total marketable securities	34,295	34,877
Level 2 \| Corporate Debt Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total marketable securities	33,496	$ 34,877
Level 2 \| Cash Equivalents \| Corporate Debt Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total marketable securities	$ 799

Fair Value Measurements - Additional Information (Details)	3 Months Ended
	Mar. 31, 2018 USD ($)
Fair Value Disclosures [Abstract]
Fair value asset, investments measured using unobservable inputs	$ 0
Fair value assets, transfers between levels, amount	0
Unrealized losses for securities in an unrealized loss position for more than 12 months	198,000
Other-than-temporary impairment losses related to marketable securities	$ 0

Fixed Assets - Major Classes of Fixed Assets (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Property Plant And Equipment [Line Items]
Fixed assets, gross	$ 11,137	$ 11,039
Less: Accumulated depreciation	(4,284)	(3,767)
Fixed assets, net	6,853	7,272
Computer Hardware
Property Plant And Equipment [Line Items]
Fixed assets, gross	$ 1,500	1,435
Useful life in years	3 years
Computer Software
Property Plant And Equipment [Line Items]
Fixed assets, gross	$ 468	463
Useful life in years	3 years
Medical Lab Equipment
Property Plant And Equipment [Line Items]
Fixed assets, gross	$ 8,136	7,145
Useful life in years	5 years
Furniture and Fixtures
Property Plant And Equipment [Line Items]
Fixed assets, gross	$ 199	159
Useful life in years	5 years
Leasehold Improvements
Property Plant And Equipment [Line Items]
Fixed assets, gross	$ 803	763
Useful life in years	Shorter of lease term or estimated useful life
Assets Not Yet Placed in Service
Property Plant And Equipment [Line Items]
Fixed assets, gross	$ 31	$ 1,074

Fixed Assets - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Property Plant And Equipment [Abstract]
Depreciation expense on fixed assets	$ 516	$ 412

Other Current Assets - Schedule of Other Current Assets (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Deferred Costs Capitalized Prepaid And Other Assets Disclosure [Abstract]
Reagents	$ 398	$ 231
Prepaid expenses	635	624
Prepaid income taxes	1,313	1,313
Marketable securities interest receivable	239	204
Other receivable	36	66
Total	$ 2,621	$ 2,438

Reporting Segment and Geographical Information - Additional Information (Details)	3 Months Ended
	Mar. 31, 2018 Segment
Segment Reporting [Abstract]
Number of reporting segments	1

Reporting Segment and Geographical Information - Summary of Revenue by Geographic Region (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Segment Reporting Information [Line Items]
Revenue	$ 4,653	$ 5,306
United States
Segment Reporting Information [Line Items]
Revenue	2,527	2,090
Canada
Segment Reporting Information [Line Items]
Revenue	970	1,083
People's Republic of China ("PRC")
Segment Reporting Information [Line Items]
Revenue	24	1,525
Other Countries
Segment Reporting Information [Line Items]
Revenue	$ 1,132	$ 608

Commitments and Contingencies - Additional Information (Details) - USD ($)		3 Months Ended
	Jan. 31, 2018	Mar. 31, 2018	Mar. 31, 2017
Commitments And Contingencies [Line Items]
Operating leases, rent expense		$ 109,000	$ 53,000
Reagents and Equipment
Commitments And Contingencies [Line Items]
Purchase obligations		$ 2,300,000
California
Commitments And Contingencies [Line Items]
Operating leases, rent expense	$ 269,000
Lease commencement date	Feb. 01, 2018
Lease expiration date	Jan. 31, 2021
Non Cancelable Operating Lease
Commitments And Contingencies [Line Items]
Operating leases term of expiration		2023-01
Operating leases, renewal term		3 years

Stockholders' Equity - Additional Information (Details) - USD ($)	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Equity [Abstract]
Unrealized holding gains (losses) on marketable securities	$ 55,000	$ 48,000

Equity-Based Compensation - Summary of Equity-Based Compensation Expenses as Part of Cost of Revenue and Operating Expenses (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Equity-based compensation expense	$ 545	$ 565
Cost of Revenue
Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Equity-based compensation expense	124	146
Research and Development
Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Equity-based compensation expense	132	211
Selling and Marketing
Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Equity-based compensation expense	108	69
General and Administrative
Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Equity-based compensation expense	$ 181	$ 139

Equity-Based Compensation - Summary of Activity for Options to Acquire Common Shares (Details) - Options - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of Units/Shares Subject to Options, Beginning Balance	465,000
Number of Units/Shares Subject to Options, Granted	0
Number of Units/Shares Subject to Options, Exercised	(5,000)
Number of Units/Shares Subject to Options, Canceled	(5,000)
Number of Units/Shares Subject to Options, Ending Balance	455,000	465,000
Number of Units/Shares Subject to Options, Exercisable	230,000
Weighted-Average Exercise Price Per Shares, Beginning Balance	$ 0.84
Weighted-Average Exercise Price Per Shares, Exercised	0.38
Weighted-Average Exercise Price Per Shares, Canceled	2.37
Weighted-Average Exercise Price Per Shares, Ending Balance	0.82	$ 0.84
Weighted-Average Exercise Price Per Shares, Exercisable	$ 0.77
Weighted-Average Remaining Contractual Life (in years)	7 years 9 months 18 days	8 years
Weighted-Average Remaining Contractual Life (in years), Exercisable	7 years 8 months 12 days
Aggregate Intrinsic Value, Balance	$ 1,584	$ 1,785
Aggregate Intrinsic Value, Exercised	17
Aggregate Intrinsic Value, Exercisable	$ 804

Equity-Based Compensation - Additional Information (Details)	3 Months Ended
	Mar. 31, 2018 USD ($) shares
Options
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Option granted \| shares	0
Total fair value of options vested	$ 163,000
Unrecognized compensation expense	$ 374,000
Expected to be recognized, weighted-average period	1 year 7 months 6 days
Restricted Stock Units (RSUs)
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected to be recognized, weighted-average period	3 years 3 months 18 days
Total compensation cost not yet recognized on grant date	$ 818,000
Compensation cost not yet recognized on grant date, period for recognition	4 years
Unrecognized compensation expense	$ 6,300,000

Equity-Based Compensation - Summary of Activity for RSUs Relating to Shares of Company's Common Stock (Details) - Restricted Stock Units (RSUs) - 2016 Omnibus Incentive Plan shares in Thousands	3 Months Ended
	Mar. 31, 2018 $ / shares shares
Number of Shares
Number of Shares, Beginning Balance \| shares	937
Number of Shares, Granted \| shares	175
Number of Shares, Vested and settled \| shares	(24)
Number of Shares, Forfeited \| shares	(20)
Number of Shares, Ending Balance \| shares	1,068
Weighted-Average Grant-Date Fair Value, Balance \| $ / shares	$ 7.39
Weighted-Average Grant-Date Fair Value, Granted \| $ / shares	4.70
Weighted-Average Grant-Date Fair Value, Vested and settled \| $ / shares	9.69
Weighted-Average Grant-Date Fair Value, Forfeited \| $ / shares	8.56
Weighted-Average Grant-Date Fair Value, Balance \| $ / shares	$ 6.88

Income Taxes - Additional Information (Details) - USD ($)	3 Months Ended		12 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Federal statutory income tax rate	21.00%		35.00%
Tax Cuts and Jobs Act of 2017, income tax expense related to revaluation of net deferred tax assets	$ 22,000
Tax Cuts and Jobs Act of 2017, unrepatriated foreign earnings	$ 0
Effective income tax rate	21.00%	31.00%

Income (Loss) Per Share - Reconciliation of Basic and Diluted Income (Loss) Per Share Computations (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Earnings Per Share [Abstract]
Net income (loss)	$ (1,910)	$ 232
Weighted-average common shares—outstanding, basic	17,864	17,676
Weighted-average common shares—outstanding, diluted	17,864	18,178
Net income (loss) per common share, basic	$ (0.11)	$ 0.01
Net income (loss) per common share, diluted	$ (0.11)	$ 0.01

- Definition

The amount of net income (loss) from continuing operations per each share of common stock or unit outstanding during the reporting period.

+ References + Details

- Definition

The amount of net income (loss) derived from continuing operations during the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period.

+ References + Details

Income (Loss) Per Share - Anti-dilutive Securities Excluded from Calculation of Diluted Income (Loss) Per Share (Details) - shares shares in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Options
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from continuing operations of diluted income (loss) per share	454	22
Restricted Stock Units (RSUs)
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from continuing operations of diluted income (loss) per share	955

Related Party - Additional Information (Details) - USD ($)	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Xilong Scientific
Related Party Transaction [Line Items]
Ownership percentage	11.00%
Fulgent Pharma
Related Party Transaction [Line Items]
Due from related parties	$ 9,000		$ 3,000
Dr. Han Lin Gao \| FF Gene Biotech \| FJIP
Related Party Transaction [Line Items]
Ownership percentage	25.00%
Research Testing Services
Related Party Transaction [Line Items]
Revenue from related parties	$ 0	$ 0
Foundation
Related Party Transaction [Line Items]
Revenue from related parties	8,000	0
Due from related parties	0		0
University
Related Party Transaction [Line Items]
Revenue from related parties	9,000	$ 12,000
Due from related parties	$ 33,000		$ 40,000

Equity Method Investments - Additional Information (Details)	1 Months Ended	3 Months Ended
	Apr. 30, 2017 CNY (¥)	Mar. 31, 2018 USD ($)	Mar. 31, 2018 CNY (¥)	Dec. 31, 2017 USD ($)
Schedule Of Equity Method Investments [Line Items]
Contribution to be made in joint venture		$ 1,692,000		$ 1,937,000
Ownership interest to be made in joint venture		30.00%	30.00%	30.00%
License Agreement
Schedule Of Equity Method Investments [Line Items]
Royalty earned		$ 18,000
FF Gene Biotech
Schedule Of Equity Method Investments [Line Items]
Contribution to be made in joint venture	¥ 60,000,000	$ 1,692,000		$ 1,937,000
Contribution period in joint venture	3 years
Ownership interest to be made in joint venture	30.00%	30.00%	30.00%	30.00%
Contributions remain for joint venture		$ 6,900,000	¥ 43,600,000
FF Gene Biotech \| Equipment
Schedule Of Equity Method Investments [Line Items]
Contributions made to joint venture		$ 2,500,000
Xilong Scientific \| FF Gene Biotech
Schedule Of Equity Method Investments [Line Items]
Contribution period in joint venture	3 years
Ownership interest to be made in joint venture	51.00%
Contribution to be made in joint venture \| ¥	¥ 102,000,000
FJIP \| FF Gene Biotech
Schedule Of Equity Method Investments [Line Items]
Contribution period in joint venture	5 years
Ownership interest to be made in joint venture	19.00%
Contribution to be made in joint venture \| ¥	¥ 19,000,000

Equity Method Investments - Schedule of Equity Method Investments (Details) $ in Thousands	Mar. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Apr. 30, 2017 CNY (¥)
Schedule Of Equity Method Investments [Line Items]
Carrying Value	$ 1,692	$ 1,937
Ownership Percentage	30.00%	30.00%
FF Gene Biotech
Schedule Of Equity Method Investments [Line Items]
Carrying Value	$ 1,692	$ 1,937	¥ 60,000,000
Ownership Percentage	30.00%	30.00%	30.00%