Changes in Equity (Details) - USD ($) $ in Thousands	3 Months Ended
	Nov. 30, 2016	Nov. 30, 2015
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance - September 1 (Beginning of period)	$ 501,432	$ 538,551
Net income (loss)	(708)	(4,967)
Other comprehensive loss, net of tax	(1,099)	(728)
Distributions to noncontrolling interests	(522)	(827)
Share repurchases	0	(3,479)
Restricted stock withheld for taxes	(3,301)	(1,887)
Share-based compensation	3,408	2,937
Dividends	(5,143)	(5,152)
Balance - November 30 (End of period)	494,067	524,448
SSI Shareholders’ Equity
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance - September 1 (Beginning of period)	497,721	534,535
Net income (loss)	(1,326)	(5,296)
Other comprehensive loss, net of tax	(1,099)	(728)
Distributions to noncontrolling interests	0	0
Share repurchases	0	(3,479)
Restricted stock withheld for taxes	(3,301)	(1,887)
Share-based compensation	3,408	2,937
Dividends	(5,143)	(5,152)
Balance - November 30 (End of period)	490,260	520,930
Noncontrolling Interests
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance - September 1 (Beginning of period)	3,711	4,016
Net income (loss)	618	329
Other comprehensive loss, net of tax	0	0
Distributions to noncontrolling interests	(522)	(827)
Share repurchases	0	0
Restricted stock withheld for taxes	0	0
Share-based compensation	0	0
Dividends	0	0
Balance - November 30 (End of period)	$ 3,807	$ 3,518