Document and Entity Information - shares	3 Months Ended
	Nov. 30, 2018	Jan. 03, 2019
Document Information [Line Items]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Nov. 30, 2018
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q1
Trading Symbol	GBX
Entity Registrant Name	GREENBRIER COMPANIES INC
Entity Central Index Key	0000923120
Current Fiscal Year End Date	--08-31
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Common Stock, Shares Outstanding		32,350,212