Condensed Consolidated Statements of Equity - USD ($) shares in Thousands, $ in Thousands	Total	Cumulative Effect, Period of Adoption, Adjustment	Cumulative Effect, Period of Adoption, Adjusted Balance	Class A Common Stock	Class B Common Stock	Common Stock Class A Common Stock	Common Stock Class A Common Stock Cumulative Effect, Period of Adoption, Adjusted Balance	Common Stock Class B Common Stock	Common Stock Class B Common Stock Cumulative Effect, Period of Adoption, Adjusted Balance	Additional Paid-in Capital	Additional Paid-in Capital Cumulative Effect, Period of Adoption, Adjusted Balance	Retained Earnings	Retained Earnings Cumulative Effect, Period of Adoption, Adjustment	Retained Earnings Cumulative Effect, Period of Adoption, Adjusted Balance	Accumulated Other Comprehensive Loss	Accumulated Other Comprehensive Loss Cumulative Effect, Period of Adoption, Adjusted Balance	Total SSI Shareholders' Equity	Total SSI Shareholders' Equity Cumulative Effect, Period of Adoption, Adjustment	Total SSI Shareholders' Equity Cumulative Effect, Period of Adoption, Adjusted Balance	Noncontrolling Interests	Noncontrolling Interests Cumulative Effect, Period of Adoption, Adjusted Balance
Beginning balance at Aug. 31, 2019	$ 701,296	$ (463)	$ 700,833			$ 26,464	$ 26,464	$ 200	$ 200	$ 33,700	$ 33,700	$ 675,363	$ (463)	$ 674,900	$ (38,763)	$ (38,763)	$ 696,964	$ (463)	$ 696,501	$ 4,332	$ 4,332
Beginning balance (in shares) at Aug. 31, 2019						26,464	26,464	200	200
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	(6,565)											(6,995)					(6,995)			430
Other comprehensive income, net of tax	238														238		238
Distributions to noncontrolling interests	(579)																			(579)
Restricted stock withheld for taxes	(5,845)					$ (274)				(5,571)							(5,845)
Restricted stock withheld for taxes (in shares)						(274)
Issuance of restricted stock						$ 753				(753)
Issuance of restricted stock (in shares)						753
Share-based compensation cost	2,152									2,152							2,152
Dividends	(5,198)											(5,198)					(5,198)
Ending balance at Nov. 30, 2019	685,036					$ 26,943		$ 200		29,528		662,707			(38,525)		680,853			4,183
Ending balance (in shares) at Nov. 30, 2019						26,943		200
Beginning balance at Aug. 31, 2020	680,436					$ 26,899		$ 200		36,616		649,863			(36,871)		676,707			3,729
Beginning balance (in shares) at Aug. 31, 2020				26,899	200	26,899		200
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	15,064											14,104					14,104			960
Other comprehensive income, net of tax	(21)														(21)		(21)
Distributions to noncontrolling interests	(723)																			(723)
Restricted stock withheld for taxes	(3,970)					$ (188)				(3,782)							(3,970)
Restricted stock withheld for taxes (in shares)						(188)
Issuance of restricted stock						$ 543				(543)
Issuance of restricted stock (in shares)						543
Share-based compensation cost	3,019									3,019							3,019
Dividends	(5,257)											(5,257)					(5,257)
Ending balance at Nov. 30, 2020	$ 688,548					$ 27,254		$ 200		$ 35,310		$ 658,710			$ (36,892)		$ 684,582			$ 3,966
Ending balance (in shares) at Nov. 30, 2020				27,254	200	27,254		200