Consolidated Statements of Income - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Aug. 31, 2020	Aug. 31, 2019	Aug. 31, 2018
Income Statement [Abstract]
Revenue	$ 1,494,111	$ 1,435,351	$ 1,350,145
Operating expenses
Cost of services	695,446	663,446	659,296
Selling, general and administrative	359,005	333,870	324,645
Total operating expenses	1,054,451	997,316	983,941
Operating income	439,660	438,035	366,204
Other expenses
Interest expense, net	(9,829)	(16,624)	(16,286)
Other (expense) income, net	(2,697)	554	1,920
Total other expense	(12,526)	(16,070)	(14,366)
Income before income taxes	427,134	421,965	351,838
Provision for income taxes	54,196	69,175	84,753
Net income	$ 372,938	$ 352,790	$ 267,085
Basic earnings per common share (in dollars per share)	$ 9.83	$ 9.25	$ 6.90
Diluted earnings per common share (in dollars per share)	$ 9.65	$ 9.08	$ 6.78
Basic weighted average common shares (in shares)	37,936	38,144	38,733
Diluted weighted average common shares (in shares)	38,646	38,873	39,377