Cover Page - shares	3 Months Ended
	Mar. 31, 2020	Apr. 28, 2020
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Mar. 31, 2020
Document Transition Report	false
Entity File Number	001-36067
Entity Registrant Name	FireEye, Inc.
Entity Incorporation, State or Country Code	DE
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
Title of 12(b) Security	Common Stock, $0.0001 par value per share
Trading Symbol	FEYE
Security Exchange Name	NASDAQ
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		222,844,478
Entity Central Index Key	0001370880
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q1
Amendment Flag	false