Income per Share - Reconciliation of Basic and Diluted Income Per Share Computations (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Earnings Per Share [Abstract]
Net income attributable to Fulgent	$ 11,537	$ 79,812	$ 165,516	$ 280,503
Weighted-average common shares—outstanding, basic	30,362	29,150	30,298	28,991
Weighted-average common shares—outstanding, diluted	31,189	30,830	31,225	30,809
Net income per common share, basic	$ 0.38	$ 2.74	$ 5.46	$ 9.68
Net income per common share, diluted	$ 0.37	$ 2.59	$ 5.30	$ 9.10