Consolidated Statements of Income - Unaudited (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Feb. 28, 2013	Feb. 29, 2012	Feb. 28, 2013	Feb. 29, 2012
Revenues	$ 213,083	$ 199,371	$ 424,167	$ 395,819
Operating expenses
Cost of services	75,842	67,531	149,427	134,364
Selling, general and administrative	81,077	64,723	147,492	127,585
Total operating expenses	156,919	132,254	296,919	261,949
Operating income	56,164	67,117	127,248	133,870
Other income	357	496	785	773
Income before income taxes	56,521	67,613	128,033	134,643
Provision for income taxes	11,982	20,867	33,726	42,353
Net income	$ 44,539	$ 46,746	$ 94,307	$ 92,290
Basic earnings per common share (in Dollars per share)	$ 1.02	$ 1.04	$ 2.14	$ 2.05
Diluted earnings per common share (in Dollars per share)	$ 1.00	$ 1.02	$ 2.11	$ 2.01
Basic weighted average common shares (in Shares)	43,813	44,880	44,065	44,993
Diluted weighted average common shares (in Shares)	44,455	45,707	44,788	45,972