Note 18 - Unaudited Quarterly Financial Data (Details) - Quarterly Financial Data (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Aug. 31, 2013	May 31, 2013	Feb. 28, 2013	Nov. 30, 2012	Aug. 31, 2012	May 31, 2012	Feb. 29, 2012	Nov. 30, 2011	Aug. 31, 2013		Aug. 31, 2012		Aug. 31, 2011
Quarterly Financial Data [Abstract]
Revenues	$ 219,332	$ 214,613	$ 213,083	$ 211,085	$ 207,663	$ 202,311	$ 199,371	$ 196,448	$ 858,112	[1]	$ 805,793	[1]	$ 726,510	[1]
Cost of services	80,231	76,721	75,842	73,586	72,295	68,878	67,531	66,833	306,379		275,537		244,623
Selling, general and administrative	68,567	66,255	81,077	66,414	64,741	64,939	64,723	62,862	282,314		257,266		243,552
Operating income	70,534	71,637	56,164	71,085	70,627	68,494	67,117	66,753	269,419		272,990		238,335
Net income	$ 50,964	$ 53,367	$ 44,539	$ 49,769	$ 48,539	$ 47,980	$ 46,746	$ 45,544	$ 198,637		$ 188,809		$ 171,046
Diluted earnings per common share (in Dollars per share)	$ 1.16	$ 1.20	$ 1.00	$ 1.11	$ 1.08	$ 1.05	$ 1.02	$ 0.99	$ 4.45		$ 4.12		$ 3.61
Weighted average common shares (diluted) (in Shares)	44,043	44,485	44,455	44,984	45,152	45,736	45,707	46,103	44,624		45,810		47,355

[1] Revenues are attributed to countries based on the location of the client.