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, 2020			$ 460.4		$ 885.5	$ (0.5)	$ (52.8)	$ 1,293.1	$ (0.5)	$ 180.0	$ 1,473.1	$ (0.5)
Beginning balance (in shares) at Aug. 31, 2020		32,700
Beginning balance at Aug. 31, 2020													$ 31.1
Accounting Standards Update [Extensible List]					ASU 2016-13			ASU 2016-13			ASU 2016-13
Net earnings (loss)	$ (20.6)				$ (19.1)			$ (19.1)		(0.4)	$ (19.5)		(1.1)
Other comprehensive income (loss), net	6.1						6.1	6.1			6.1
Noncontrolling interest adjustments										(1.3)	(1.3)
Joint venture partner distribution declared										(2.4)	(2.4)
Restricted stock awards (net of cancellations)			15.5					15.5			15.5
Restricted stock awards (net of cancellations) (in shares)		100
Unamortized restricted stock			(17.9)					(17.9)			(17.9)
Restricted stock amortization			9.0					9.0			9.0
Cash dividends					(17.7)			(17.7)			(17.7)
Ending balance at Feb. 28, 2021			467.0		848.2		(46.7)	1,268.5		175.9	1,444.4
Ending Balance (in shares) at Feb. 28, 2021		32,800
Ending Balance at Feb. 28, 2021													30.0
Beginning balance at Nov. 30, 2020			462.5		866.4		(48.5)	1,280.4		180.5	1,460.9
Beginning balance (in shares) at Nov. 30, 2020		32,800
Beginning balance at Nov. 30, 2020													30.7
Net earnings (loss)	(13.9)				(9.1)			(9.1)		(4.2)	(13.3)		(0.7)
Other comprehensive income (loss), net	1.8						1.8	1.8			1.8
Joint venture partner distribution declared										(0.4)	(0.4)
Restricted stock awards (net of cancellations)			1.3					1.3			1.3
Unamortized restricted stock			(1.3)					(1.3)			(1.3)
Restricted stock amortization			4.5					4.5			4.5
Cash dividends					(9.1)			(9.1)			(9.1)
Ending balance at Feb. 28, 2021			467.0		848.2		(46.7)	1,268.5		175.9	1,444.4
Ending Balance (in shares) at Feb. 28, 2021		32,800
Ending Balance at Feb. 28, 2021													30.0
Beginning balance at Aug. 31, 2021	$ 1,476.4		$ 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	32,397	32,400
Beginning balance at Aug. 31, 2021													29.7
Accounting Standards Update [Extensible List]			ASU 2020-06		ASU 2020-06			ASU 2020-06			ASU 2020-06
Net earnings (loss)	$ 16.8				$ 23.6			$ 23.6		(5.6)	$ 18.0		(1.2)
Other comprehensive income (loss), 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)
Restricted stock amortization			5.9					5.9			5.9
Cash dividends					(17.7)			(17.7)			(17.7)
Ending balance at Feb. 28, 2022	$ 1,406.7	$ 32.6	413.4		892.5		(53.3)	1,252.6		154.1	1,406.7		28.5
Ending Balance (in shares) at Feb. 28, 2022	32,588	32,600
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 (loss)	$ 11.2				12.8			12.8		(0.4)	12.4		(1.2)
Other comprehensive income (loss), 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
Repurchase of stock								9.0			9.0
Cash dividends					(9.0)
Ending balance at Feb. 28, 2022	$ 1,406.7	$ 32.6	$ 413.4		$ 892.5		$ (53.3)	$ 1,252.6		$ 154.1	$ 1,406.7		$ 28.5
Ending Balance (in shares) at Feb. 28, 2022	32,588	32,600