Consolidated Statements of Equity - USD ($) shares in Thousands, $ in Thousands	Total	Additional Paid-in Capital	Retained Earnings	Accumulated Other Comprehensive Loss	Total SSI Shareholders’ Equity	Noncontrolling Interests	Class A Common Stock	Class A Common Stock Common Stock	Class B Common Stock	Class B Common Stock Common Stock
Beginning balance at Aug. 31, 2016	$ 501,432	$ 30,948	$ 480,100	$ (40,115)	$ 497,721	$ 3,711		$ 26,482		$ 306
Beginning balance (in shares) at Aug. 31, 2016								26,482		306
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	46,978		44,511		44,511	2,467
Other comprehensive income (loss), net of tax	4,822			4,822	4,822
Distributions to noncontrolling interests	(2,271)					(2,271)
Conversion of common stock								$ 106		$ (106)
Conversion of common stock (in shares)								106		(106)
Restricted stock withheld for taxes	(3,474)	(3,326)			(3,474)			$ (148)
Restricted stock withheld for taxes (in shares)								(148)
Issuance of restricted stock		(419)						$ 419
Issuance of restricted stock (in shares)								419
Share-based compensation expense	10,847	10,847			10,847
Dividends	(20,841)		(20,841)		(20,841)
Ending balance at Aug. 31, 2017	537,493	38,050	503,770	(35,293)	533,586	3,907		$ 26,859		$ 200
Ending balance (in shares) at Aug. 31, 2017								26,859		200
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	159,789		156,451		156,451	3,338
Other comprehensive income (loss), net of tax	(1,944)			(1,944)	(1,944)
Reclassification of stranded tax effects of the Tax Act	517		517		517
Distributions to noncontrolling interests	(2,796)					(2,796)
Purchase of noncontrolling interest	(600)		(183)		(183)	(417)
Share repurchases	(17,361)	(16,845)			(17,361)			$ (516)
Share repurchase (in shares)								(516)
Restricted stock withheld for taxes	(3,082)	(2,979)			(3,082)			$ (103)
Restricted stock withheld for taxes (in shares)								(103)
Issuance of restricted stock		(262)						$ 262
Issuance of restricted stock (in shares)								262
Share-based compensation expense	18,965	18,965			18,965
Dividends	(20,871)		(20,871)		(20,871)
Ending balance at Aug. 31, 2018	670,110	36,929	639,684	(37,237)	666,078	4,032		$ 26,502		$ 200
Ending balance (in shares) at Aug. 31, 2018							26,502	26,502	200	200
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	58,322		56,345		56,345	1,977
Other comprehensive income (loss), net of tax	(1,526)			(1,526)	(1,526)
Distributions to noncontrolling interests	(1,677)					(1,677)
Share repurchases	(13,083)	(12,556)			(13,083)			$ (527)
Share repurchase (in shares)								(527)
Restricted stock withheld for taxes	(7,484)	(7,206)			(7,484)			$ (278)
Restricted stock withheld for taxes (in shares)								(278)
Issuance of restricted stock		(767)						$ 767
Issuance of restricted stock (in shares)								767
Share-based compensation expense	17,300	17,300			17,300
Dividends	(20,666)		(20,666)		(20,666)
Ending balance at Aug. 31, 2019	$ 701,296	$ 33,700	$ 675,363	$ (38,763)	$ 696,964	$ 4,332		$ 26,464		$ 200
Ending balance (in shares) at Aug. 31, 2019							26,464	26,464	200	200