Business Combinations (Details) (USD $)	3 Months Ended		9 Months Ended		12 Months Ended
	May 31, 2011		May 31, 2011		Aug. 31, 2011 acquisition
Business Acquisition [Line Items]
Number of Acquisitions Accounted For As Business Combinations					10
Business Acquisition, Cost of Acquired Entity, Purchase Price					$ 316,000,000
Business Acquisition, Cost of Acquired Entity, Cash Paid					294,000,000
Business Acquisition, Cost of Acquired Entity, Other Consideration					22,000,000
Business Acquisition, Contingent Consideration, at Fair Value					2,000,000
Business Acquisition, Purchase Price Allocation, Goodwill Amount					253,000,000
Unaudited pro forma financial information [Abstract]
Revenues	991,979,000		2,458,491,000
Operating income	58,201,000	[1]	149,539,000	[1]
Net income	36,309,000	[1]	98,315,000	[1]
Net income attributable to SSI	34,617,000	[1]	92,715,000	[1]
Wholly Owned Acquisition Subsidiary [Member]
Business Acquisition [Line Items]
Business Acquisition, Cost of Acquired Entity, Equity Interests Issued and Issuable					$ 20,000,000

[1] Excludes nonrecurring executive compensation paid to the management of acquired companies that will not be incurred in the future.