| Document and Entity Information | Nov. 03, 2023 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Amendment Flag | false |
| Document Period End Date | Nov. 03, 2023 |
| Entity Registrant Name | FULGENT GENETICS, INC. |
| Entity Central Index Key | 0001674930 |
| Securities Act File Number | 001-37894 |
| Entity Incorporation, State or Country Code | DE |
| Entity Tax Identification Number | 81-2621304 |
| Entity Address, Address Line One | 4399 Santa Anita Avenue |
| Entity Address, City or Town | El Monte |
| Entity Address, State or Province | CA |
| Entity Address, Postal Zip Code | 91731 |
| City Area Code | 626 |
| Local Phone Number | 350-0537 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Entity Emerging Growth Company | false |
| Title of 12(b) Security | Common Stock, par value $0.0001 per share |
| Trading Symbol | FLGT |
| Security Exchange Name | NASDAQ |
