Schedule of Summarized Financial Data (Detail) - USD ($) $ in Thousands		3 Months Ended								12 Months Ended
		Aug. 31, 2017	May 31, 2017	Feb. 28, 2017	Nov. 30, 2016	Aug. 31, 2016	May 31, 2016	Feb. 28, 2016	Nov. 30, 2015	Aug. 31, 2017		Aug. 31, 2016		Aug. 31, 2015
Schedule of Equity Method Investments [Line Items]
Total assets		$ 2,397,705				$ 1,835,774				$ 2,397,705		$ 1,835,774		$ 1,787,452
Revenue		611,407	$ 439,161	$ 566,282	$ 552,314	595,190	$ 612,866	$ 669,079	$ 802,389	2,169,164	[1]	2,679,524	[1]	2,605,278	[1]
Margin		99,922	89,701	118,925	112,751	119,683	127,098	119,891	184,765	421,299		551,437		537,353
Net income (loss)		23,746	$ 32,823	$ 34,536	$ 24,962	33,560	$ 35,352	$ 44,868	$ 69,433	116,067		183,213		192,832
GBW Railcar Services LLC
Schedule of Equity Method Investments [Line Items]
Current assets		81,860				109,651				81,860		109,651
Total assets	[2]	206,009				247,610				206,009		247,610		239,871
Current liabilities		33,033				37,123				33,033		37,123
Total liabilities		111,384				116,077				111,384		116,077
Revenue										253,436		373,490		349,849
Margin										(4,058)		33,929		21,752
Net income (loss)	[3]									(36,947)		4,006		(2,551)
Greenbrier-Maxion
Schedule of Equity Method Investments [Line Items]
Current assets		48,012				49,104				48,012		49,104
Total assets		71,455				70,788				71,455		70,788
Current liabilities		38,055				59,967				38,055		59,967
Total liabilities		42,197				63,242				42,197		63,242
Revenue										228,510		168,465		71,204
Margin										24,372		14,245		6,323
Net income (loss)										1,378		(4,051)		805
Amsted-Maxion Cruzeiro
Schedule of Equity Method Investments [Line Items]
Current assets		23,777				22,944				23,777		22,944
Total assets		142,583				164,182				142,583		164,182
Current liabilities		28,084				59,696				28,084		59,696
Total liabilities		94,846				100,872				94,846		100,872
Revenue										90,114		87,833		36,696
Margin										5,983		8,256		4,083
Net income (loss)										(20,114)		(12,640)		48,113
Other Unconsolidated Affiliates
Schedule of Equity Method Investments [Line Items]
Current assets		16,996				19,852				16,996		19,852
Total assets		283,895				162,073				283,895		162,073
Current liabilities		3,003				6,586				3,003		6,586
Total liabilities		$ 90,064				$ 6,951				90,064		6,951
Revenue										39,161		75,851		98,385
Margin										8,015		11,087		14,025
Net income (loss)										$ 5,202		$ 6,051		$ 10,022

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

[2] Includes goodwill and intangible assets of $78.8 million, $93.4 million and $96.9 million as of August 31, 2017, 2016 and 2015, respectively. In 2017, GBW recorded a pre-tax goodwill impairment loss of $11.2 million which reduced the goodwill balance to $41.5 million.

[3] In 2017, GBW recorded a pre-tax goodwill impairment loss of $11.2 million which reduced the goodwill balance to $41.5 million. The Company's portion of the non-cash goodwill impairment was $3.5 million after-tax.