Approach to Calculate Diluted Earning Per Share (Detail) - Entity [Domain] - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands		3 Months Ended		9 Months Ended
		May. 31, 2015	May. 31, 2014	May. 31, 2015	May. 31, 2014
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Net earnings attributable to Greenbrier		$ 42,811	$ 33,588	$ 125,948	$ 64,563
Weighted average diluted common shares outstanding		33,000	34,001	33,262	34,268
Diluted earnings per share	[1]	$ 1.33	$ 1.03	$ 3.91	$ 2.01
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		$ 1,234	$ 1,416	$ 4,066	$ 4,248
Earnings before interest and debt issuance costs on convertible notes		$ 44,045	$ 35,004	$ 130,014	$ 68,811

[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