Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2018	Oct. 31, 2018
Document and Entity Information [Abstract]
Entity Registrant Name	FIREEYE, INC.
Entity Central Index Key	0001370880
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Document Type	10-Q
Document Period End Date	Sep. 30, 2018
Document Fiscal Year Focus	2018
Document Fiscal Period Focus	Q3
Emerging Growth Company	false
Small Business	false
Amendment Flag	false
Entity Common Stock, Shares Outstanding		197,014,986