Changes in Equity (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Feb. 28, 2017	Feb. 29, 2016	Feb. 28, 2017	Feb. 29, 2016
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance - September 1 (Beginning of period)			$ 501,432	$ 538,551
Net income (loss)	$ 11,699	$ (40,970)	10,991	(45,937)
Other comprehensive loss, net of tax	320	(828)	(779)	(1,556)
Distributions to noncontrolling interests			(852)	(971)
Share repurchases			0	(3,479)
Restricted stock withheld for taxes			(3,301)	(1,895)
Share-based compensation			5,570	2,627
Dividends			(10,377)	(10,268)
Balance - February 28, 2017 and February 29, 2016 (End of period)	502,684	477,072	502,684	477,072
SSI Shareholders’ Equity
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance - September 1 (Beginning of period)			497,721	534,535
Net income (loss)			9,711	(46,541)
Other comprehensive loss, net of tax			(779)	(1,556)
Distributions to noncontrolling interests			0	0
Share repurchases			0	(3,479)
Restricted stock withheld for taxes			(3,301)	(1,895)
Share-based compensation			5,570	2,627
Dividends			(10,377)	(10,268)
Balance - February 28, 2017 and February 29, 2016 (End of period)	498,545	473,423	498,545	473,423
Noncontrolling Interests
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance - September 1 (Beginning of period)			3,711	4,016
Net income (loss)			1,280	604
Other comprehensive loss, net of tax			0	0
Distributions to noncontrolling interests			(852)	(971)
Share repurchases			0	0
Restricted stock withheld for taxes			0	0
Share-based compensation			0	0
Dividends			0	0
Balance - February 28, 2017 and February 29, 2016 (End of period)	$ 4,139	$ 3,649	$ 4,139	$ 3,649