Net Income Per Share (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Feb. 28, 2013	Feb. 29, 2012	Feb. 28, 2013	Feb. 29, 2012
Earnings Per Share [Abstract]
Net income	$ 8,743	$ 10,365	$ 7,299	$ 18,107
Net income attributable to noncontrolling interests	(100)	(735)	(329)	(1,462)
Net income attributable to SSI	$ 8,643	$ 9,630	$ 6,970	$ 16,645
Computation of shares:
Weighted average common shares outstanding, basic	26,640,000	27,509,000	26,597,000	27,480,000
Incremental common shares attributable to dilutive stock options, performance share awards, DSUs and RSUs	141,000	272,000	154,000	254,000
Weighted average common shares outstanding, diluted	26,781,000	27,781,000	26,751,000	27,734,000
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	599,184,000	57,364,000	622,664,000	92,107,000