Condensed Consolidated Statements of Equity - USD ($) shares in Thousands, $ in Millions	Total	Common Stock Shares	Additional Paid-in Capital	Additional Paid-in Capital Cumulative Effect Adjustment Due to Adoption	Retained Earnings	Retained Earnings Cumulative Effect Adjustment Due to Adoption	Accumulated Other Comprehensive (Loss)	Total Equity - Greenbrier	Total Equity - Greenbrier Cumulative Effect Adjustment Due to Adoption	Noncontrolling Interest	Equity Excluding Contingently Redeemable Noncontrolling Interest	Equity Excluding Contingently Redeemable Noncontrolling Interest Cumulative Effect Adjustment Due to Adoption	Contingently Redeemable Noncontrolling Interest
Beginning balance at Aug. 31, 2021			$ 469.7	$ (58.8)	$ 881.7	$ 4.9	$ (43.7)	$ 1,307.7	$ (53.9)	$ 168.7	$ 1,476.4	$ (53.9)
Beginning balance (in shares) at Aug. 31, 2021		32,400
Beginning balance at Aug. 31, 2021													$ 29.7
Accounting Standards Update [Extensible List]			us-gaap:AccountingStandardsUpdate202006Member		us-gaap:AccountingStandardsUpdate202006Member			us-gaap:AccountingStandardsUpdate202006Member			us-gaap:AccountingStandardsUpdate202006Member
Net earnings	$ 16.8				$ 23.6			$ 23.6		(5.6)	$ 18.0		(1.2)
Other comprehensive income, net	(9.6)						(9.6)	(9.6)			(9.6)
Noncontrolling interest adjustments										(0.6)	(0.6)
Joint venture partner distribution declared										(8.4)	(8.4)
Restricted stock awards (net of cancellations)			$ 11.9					11.9			11.9
Restricted stock awards (net of cancellations) (in shares)		200
Unamortized restricted stock			(15.3)					(15.3)			(15.3)
Stock based compensation expense			5.9					5.9			5.9
Cash dividends					(17.7)			(17.7)			(17.7)
Ending balance at Feb. 28, 2022			413.4		892.5		(53.3)	1,252.6		154.1	1,406.7
Ending Balance (in shares) at Feb. 28, 2022		32,600
Ending Balance at Feb. 28, 2022													28.5
Beginning balance at Nov. 30, 2021			408.5		888.7		(59.9)	1,237.3		162.7	1,400.0
Beginning balance (in shares) at Nov. 30, 2021		32,500
Beginning balance at Nov. 30, 2021													29.7
Net earnings	11.2				12.8			12.8		(0.4)	12.4		(1.2)
Other comprehensive income, net	6.6						6.6	6.6			6.6
Noncontrolling interest adjustments										(0.4)	(0.4)
Joint venture partner distribution declared										(7.8)	(7.8)
Restricted stock awards (net of cancellations)			1.4					1.4			1.4
Restricted stock awards (net of cancellations) (in shares)		100
Unamortized restricted stock			(1.3)					(1.3)			(1.3)
Restricted stock amortization			4.8					4.8			4.8
Cash dividends					(9.0)			(9.0)			(9.0)
Ending balance at Feb. 28, 2022			413.4		892.5		(53.3)	1,252.6		154.1	1,406.7
Ending Balance (in shares) at Feb. 28, 2022		32,600
Ending Balance at Feb. 28, 2022													28.5
Beginning balance at Aug. 31, 2022	$ 1,429.1		424.8		897.7		(45.6)	1,276.9		152.2	1,429.1
Beginning balance (in shares) at Aug. 31, 2022	32,603	32,600
Beginning balance at Aug. 31, 2022													27.7
Net earnings	$ 19.5				16.4			16.4		3.3	19.7		(0.2)
Other comprehensive income, net	23.9						23.9	23.9			23.9
Noncontrolling interest adjustments			(7.9)					(7.9)		(2.0)	(9.9)
Joint venture partner distribution declared										(8.9)	(8.9)
Restricted stock awards (net of cancellations)			9.0					9.0			9.0
Restricted stock awards (net of cancellations) (in shares)		200
Unamortized restricted stock			(11.4)					(11.4)			(11.4)
Stock based compensation expense			5.9					5.9			5.9
Repurchase of stock			(17.4)					(17.4)			(17.4)
Repurchase of stock (in shares)		(500)
Cash dividends					(18.1)			(18.1)			(18.1)
Ending balance at Feb. 28, 2023	$ 1,421.9		403.0		896.0		(21.7)	1,277.3		144.6	1,421.9
Ending Balance (in shares) at Feb. 28, 2023	32,262	32,300
Ending Balance at Feb. 28, 2023													27.5
Beginning balance at Nov. 30, 2022			425.6		871.9		(31.7)	1,265.8		152.1	1,417.9
Beginning balance (in shares) at Nov. 30, 2022		32,800
Beginning balance at Nov. 30, 2022													27.7
Net earnings	$ 36.8				33.1			33.1		3.9	37.0		(0.2)
Other comprehensive income, net	10.0						10.0	10.0			10.0
Noncontrolling interest adjustments			(7.9)					(7.9)		(7.5)	(15.4)
Joint venture partner distribution declared										(3.9)	(3.9)
Restricted stock awards (net of cancellations)			0.5					0.5			0.5
Unamortized restricted stock			(0.5)					(0.5)			(0.5)
Stock based compensation expense			2.7					2.7			2.7
Repurchase of stock			(17.4)					(17.4)			(17.4)
Repurchase of stock (in shares)		(500)
Cash dividends					(9.0)			(9.0)			(9.0)
Ending balance at Feb. 28, 2023	$ 1,421.9		$ 403.0		$ 896.0		$ (21.7)	$ 1,277.3		$ 144.6	$ 1,421.9
Ending Balance (in shares) at Feb. 28, 2023	32,262	32,300
Ending Balance at Feb. 28, 2023													$ 27.5