Approach to Calculate Diluted Earning Per Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands		3 Months Ended
		Nov. 30, 2016	Nov. 30, 2015
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Net earnings attributable to Greenbrier		$ 24,962	$ 69,433
Earnings before interest and debt issuance costs on convertible notes		$ 25,695	$ 69,929
Weighted average diluted common shares outstanding		32,412	32,578
Diluted earnings per share	[1]	$ 0.79	$ 2.15
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	$ 496

[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