Approach to Calculate Diluted Earning Per Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands		3 Months Ended		9 Months Ended
		May 31, 2016	May 31, 2015	May 31, 2016	May 31, 2015
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Net earnings attributable to Greenbrier		$ 35,352	$ 42,811	$ 149,653	$ 125,948
Earnings before interest and debt issuance costs on convertible notes		$ 36,085	$ 44,045	$ 151,615	$ 130,014
Weighted average diluted common shares outstanding		32,342	33,000	32,475	33,262
Diluted earnings per share	[1]	$ 1.12	$ 1.33	$ 4.67	$ 3.91
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		$ 733	$ 1,234	$ 1,962	$ 4,066

[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