Consolidated Statements of Equity - USD ($) shares in Thousands, $ in Thousands	Total	Contingently Redeemable Noncontrolling Interest	Common Stock Shares	Additional Paid-in Capital	Retained Earnings	Accumulated Other Comprehensive Income (Loss)	Total Attributable to Greenbrier	Attributable to Noncontrolling Interest	Equity Excluding Contingently Redeemable Noncontrolling Interest [Member]	2024 Convertible Senior Notes Additional Paid-in Capital	2024 Convertible Senior Notes Total Attributable to Greenbrier	2024 Convertible Senior Notes Equity Excluding Contingently Redeemable Noncontrolling Interest [Member]	2024 Convertible Senior Notes Issuance Costs Additional Paid-in Capital	2024 Convertible Senior Notes Issuance Costs Total Attributable to Greenbrier	2024 Convertible Senior Notes Issuance Costs Equity Excluding Contingently Redeemable Noncontrolling Interest [Member]
Beginning balance (in shares) at Aug. 31, 2015			28,907
Beginning balance at Aug. 31, 2015				$ 295,444	$ 458,599	$ (21,205)	$ 732,838	$ 130,651	$ 863,489
Net earnings	$ 284,824
Net earnings					183,213		183,213	101,611	284,824
Other comprehensive income, net	(5,586)					(5,548)	(5,548)	(38)	(5,586)
Noncontrolling interest adjustments								526	526
Noncontrolling interest acquired								(1,195)	(1,195)
Joint venture partner distribution declared								(94,439)	(94,439)
Investment by joint venture partner								5,400	5,400
Restricted stock awards (net of cancellations) (in shares)			353
Restricted stock awards (net of cancellations)				6,055			6,055		6,055
Unamortized restricted stock				(11,555)			(11,555)		(11,555)
Restricted stock amortization				22,502			22,502		22,502
Excess tax benefit from restricted stock awards				2,813			2,813		2,813
Dividends					(23,634)		(23,634)		(23,634)
Repurchase of stock (in shares)			(1,055)
Repurchase of stock				(32,373)			(32,373)		(32,373)
Ending Balance (in shares) at Aug. 31, 2016			28,205
Ending Balance at Aug. 31, 2016				282,886	618,178	(26,753)	874,311	142,516	1,016,827
Net earnings	160,462				116,067		116,067	46,535	162,602
Beginning balance at Aug. 31, 2016		$ (2,140)
Contingently redeemable noncontrolling interest		38,288
Other comprehensive income, net	$ 20,496					20,474	20,474	22	20,496
Noncontrolling interest adjustments								(677)	(677)
Joint venture partner distribution declared								(28,027)	(28,027)
Acquisition of minority interest								394	394
Restricted stock awards (net of cancellations) (in shares)			298
Restricted stock awards (net of cancellations)				5,520			5,520		5,520
Unamortized restricted stock				(10,734)			(10,734)		(10,734)
Restricted stock amortization				19,826			19,826		19,826
Tax deficiency from restricted stock awards				(2,339)			(2,339)		(2,339)
Dividends					(25,142)		(25,142)		(25,142)
2024 Convertible Senior Notes - equity component, net of tax										$ 20,818	$ 20,818	$ 20,818	$ (671)	$ (671)	$ (671)
Ending Balance (in shares) at Aug. 31, 2017	28,503		28,503
Ending Balance at Aug. 31, 2017	$ 1,178,893	36,148		315,306	709,103	(6,279)	1,018,130	160,763	1,178,893
Net earnings	172,063				151,781		151,781	26,662	178,443
Beginning balance at Aug. 31, 2017		(6,380)
Other comprehensive income, net	$ (17,106)					(17,087)	(17,087)	(19)	(17,106)
Noncontrolling interest adjustments								2,864	2,864
Noncontrolling interest acquired								(7)	(7)
Joint venture partner distribution declared								(62,649)	(62,649)
Investment by joint venture partner								6,500	6,500
Restricted stock awards (net of cancellations) (in shares)			336
Restricted stock awards (net of cancellations)				7,334			7,334		7,334
Unamortized restricted stock				(15,058)			(15,058)		(15,058)
Restricted stock amortization				16,100			16,100		16,100
Dividends					(29,986)		(29,986)		(29,986)
Conversion of 2018 Convertible Senior Notes (in shares)			3,352
Conversion of 2018 Convertible Senior Notes				118,887			118,887		118,887
Ending Balance (in shares) at Aug. 31, 2018	32,191		32,191
Ending Balance at Aug. 31, 2018	$ 1,384,215	$ 29,768		$ 442,569	$ 830,898	$ (23,366)	$ 1,250,101	$ 134,114	$ 1,384,215