Document and Entity Information - shares	6 Months Ended
	Feb. 28, 2019	Mar. 29, 2019
Document and Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Feb. 28, 2019
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q2
Entity Registrant Name	GREENBRIER COMPANIES INC
Entity Central Index Key	0000923120
Current Fiscal Year End Date	--08-31
Entity Filer Category	Large Accelerated Filer
Trading Symbol	GBX
Entity Emerging Growth Company	false
Entity Small Business	false
Entity Common Stock, Shares Outstanding		32,406,264