Acquisitions - Additional Information (Detail) € in Millions		3 Months Ended								12 Months Ended
	Jun. 01, 2017 EUR (€)	Aug. 31, 2017 USD ($)	May 31, 2017 USD ($)	Feb. 28, 2017 USD ($)	Nov. 30, 2016 USD ($)	Aug. 31, 2016 USD ($)	May 31, 2016 USD ($)	Feb. 28, 2016 USD ($)	Nov. 30, 2015 USD ($)	Aug. 31, 2017 USD ($)		Aug. 31, 2016 USD ($)		Aug. 31, 2015 USD ($)		Jun. 01, 2017 USD ($)
Business Acquisition [Line Items]
Revenue		$ 611,407,000	$ 439,161,000	$ 566,282,000	$ 552,314,000	$ 595,190,000	$ 612,866,000	$ 669,079,000	$ 802,389,000	$ 2,169,164,000	[1]	$ 2,679,524,000	[1]	$ 2,605,278,000	[1]
Earnings (loss) from operations		$ 57,780,000	$ 48,472,000	$ 81,520,000	$ 72,660,000	$ 83,545,000	$ 84,129,000	$ 92,393,000	$ 148,485,000	$ 260,432,000		$ 408,552,000		$ 386,892,000
Greenbrier-Astra Rail
Business Acquisition [Line Items]
Ownership percentage by parent		75.00%								75.00%						75.00%
Amount to be paid at closing | €	€ 30
Amount to be paid 12 months after closing by providing a guarantee | €	€ 30
Percentage of noncontrolling interest																25.00%
Net assets acquired																$ 114,595,000
Noncontrolling interest, fair value of acquisition																$ 38,300,000
Adjustments to reconcile carrying value of redemption amount to recorded retained earnings										$ 0
Revenue										23,900,000
Earnings (loss) from operations										$ 3,000,000

[1] Revenue is presented on the basis of geographic location of customers.