Approach to Calculate Diluted Earning Per Share (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended			9 Months Ended
	May 31, 2013	May 31, 2012		May 31, 2013	May 31, 2012
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Net earnings attributable to Greenbrier	$ (56,030)	$ 19,117		$ (31,764)	$ 51,303
Earnings before interest and debt issuance costs on convertible notes		20,533			55,565
Weighted average diluted common shares outstanding	26,619	33,862		26,510	33,640
Diluted earnings per share	$ (2.10)	$ 0.61	[1]	$ (1.20)	$ 1.65	[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		$ 1,416			$ 4,262

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