Selected Quarterly Financial Data (Unaudited) - Unaudited Quarterly Data (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2022	Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2022	Dec. 31, 2021	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Statement of Operations Data:
Revenue	$ 67,704	$ 105,655	$ 125,341	$ 320,268	$ 251,671	$ 227,868	$ 153,616	$ 359,429	$ 618,968	$ 992,584	$ 421,712
Cost of revenue	54,717	59,560	60,065	77,725	62,134	43,466	35,858	74,075	252,067	215,533	89,807
Gross profit	12,987	46,095	65,276	242,543	189,537	184,402	117,758	285,354	366,901	777,051	331,905
Operating expenses:
Research and development	8,509	7,507	6,905	5,989	7,464	6,021	5,312	5,422	28,910	24,219	11,580
Selling and marketing	10,253	9,859	10,866	7,940	8,200	6,012	5,219	5,008	38,918	24,439	14,952
General and administrative	28,793	26,266	30,240	25,775	22,102	12,299	8,329	8,002	111,074	50,732	15,215
Amortization of intangible assets	2,010	2,006	1,575	906	911	797			6,497	1,708
Restructuring costs	(26)	105	2,896						2,975
Total operating expenses	49,539	45,743	52,482	40,610	38,677	25,129	18,860	18,432	188,374	101,098	41,747
Operating (loss) income	(36,552)	352	12,794	201,933	150,860	159,273	98,898	266,922	178,527	675,953	290,158
Interest and other income (expense), net	3,090	1,405	958	45	(35)	496	604	282
(Loss) Income before income taxes, equity loss in investee and gain (loss) on equity-method investments	(33,462)	1,757	13,752	201,978	150,825	159,769	99,502	267,204	184,025	677,300	291,684
(Benefit from) provision for income taxes	(9,386)	414	2,653	48,421	47,148	37,545	23,589	66,513	42,102	174,795	72,532
(Loss) income before gain on equity method investment	(24,076)	1,343	11,099	153,557	103,677	122,224	75,913	200,691
Gain on equity method investment							3,734
Net (loss) income from consolidated operations	(24,076)	1,343	11,099	153,557	103,677	122,224	79,647	200,691	141,923	506,239	214,310
Net loss attributable to noncontrolling interests	244	376	438	422	662	298	165		1,480	1,125
Net (loss) income attributable to Fulgent	$ (23,832)	$ 1,719	$ 11,537	$ 153,979	$ 104,339	$ 122,522	$ 79,812	$ 200,691	$ 143,403	$ 507,364	$ 214,310
Net (loss) income per common share attributable to Fulgent:
Basic	$ (0.80)	$ 0.06	$ 0.38	$ 5.09	$ 3.48	$ 4.13	$ 2.74	$ 6.96	$ 4.76	$ 17.25	$ 9.44
Diluted	$ (0.80)	$ 0.06	$ 0.37	$ 4.93	$ 3.34	$ 3.93	$ 2.59	$ 6.52	$ 4.63	$ 16.38	$ 8.91