Approach to Calculate Diluted Earning Per Share (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended
	Nov. 30, 2012		Nov. 30, 2011
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Net earnings attributable to Greenbrier	$ 10,427		$ 14,517
Earnings before interest and debt issuance costs on convertible notes	$ 11,857,000		$ 15,893,000
Weighted average diluted common shares outstanding	33,991		33,389
Diluted earnings per share	$ 0.35	[1]	$ 0.48	[1]
2026 Senior Notes
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Interest and debt issuance costs on the 2018 Convertible notes, net of tax	$ 1,430		$ 1,376

[1] Diluted earnings per share was calculated as follows: Earnings before interest and debt issuance costs on convertible notes Weighted average diluted common shares outstanding