Approach to Calculate Diluted Earning Per Share (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended
	Nov. 30, 2014		Nov. 30, 2013
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Net earnings attributable to Greenbrier	$ 32,786		$ 15,388
Weighted average diluted common shares outstanding	33,713		34,462
Diluted earnings per share	$ 1.01	[1]	$ 0.49	[1]
2018 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		1,416
Earnings before interest and debt issuance costs on convertible notes	$ 34,202		$ 16,804

[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