| Document and Entity Information | Dec. 11, 2020 |
| Cover [Abstract] | |
| Amendment Flag | false |
| Entity Central Index Key | 0001370880 |
| Document Type | 8-K |
| Document Period End Date | Dec. 11, 2020 |
| Entity Registrant Name | FireEye, Inc. |
| Entity Incorporation State Country Code | DE |
| Entity File Number | 001-36067 |
| Entity Tax Identification Number | 20-1548921 |
| Entity Address, Address Line One | 601 McCarthy Blvd. |
| Entity Address, City or Town | Milpitas |
| Entity Address, State or Province | CA |
| Entity Address, Postal Zip Code | 95035 |
| City Area Code | (408) |
| Local Phone Number | 321-6300 |
| Written Communications | false |
| Soliciting Material | false |
| Pre Commencement Tender Offer | false |
| Pre Commencement Issuer Tender Offer | false |
| Security 12b Title | Common Stock, par value $0.0001 per share |
| Trading Symbol | FEYE |
| Security Exchange Name | NASDAQ |
| Entity Emerging Growth Company | false |
