Consolidated Statements of Changes In Stockholders' Equity - USD ($) $ in Thousands	Common Stock [Member]	Additional Paid-in Capital [Member]	Treasury Stock [Member]	Retained Earnings [Member]	AOCI Attributable to Parent [Member]	Total
Balance, beginning of year at Aug. 31, 2014	$ 491	$ 413,754	$ (734,746)	$ 849,504	$ (17,921)	$ 511,082
Common stock issued for employee stock plans	12	72,381				72,393
Stock-based compensation expense		26,371				26,371
Tax benefits from share-based payment arrangements		28,948				28,948
Accelerated share repurchase
Stock-based compensation adjustment associated with disposition
Stock issued for acquisition of business		901	2,090			2,991
Repurchases of common stock			(253,076)			(253,076)
Accelerated share repurchase
Purchases of common stock upon restricted stock vesting			(3,141)			(3,141)
Net income				241,051		241,051
Dividends				(68,904)		(68,904)
Foreign currency translation adjustments					(25,263)	(25,263)
Net unrealized gain (loss) on cash flow hedges, net of tax					(868)	(868)	[1]
Balance, end of year at Aug. 31, 2015	503	542,355	(988,873)	1,021,651	(44,052)	531,584
Common stock issued for employee stock plans	9	57,784				57,793
Stock-based compensation expense		29,793				29,793
Tax benefits from share-based payment arrangements		18,205				18,205
Accelerated share repurchase		(24,000)
Stock-based compensation adjustment associated with disposition		(942)				(942)
Stock issued for acquisition of business
Repurchases of common stock			(328,283)			(352,283)
Accelerated share repurchase
Purchases of common stock upon restricted stock vesting			(4,544)			(4,544)
Net income				338,815		338,815
Dividends				(76,539)		(76,539)
Foreign currency translation adjustments					(23,644)	(23,644)
Net unrealized gain (loss) on cash flow hedges, net of tax					(857)	(857)	[1]
Balance, end of year at Aug. 31, 2016	512	623,195	(1,321,700)	1,283,927	(68,553)	517,381
Common stock issued for employee stock plans	6	50,039				50,045
Stock-based compensation expense		34,183				34,183
Tax benefits from share-based payment arrangements		10,331				10,331
Accelerated share repurchase		24,000
Stock-based compensation adjustment associated with disposition
Stock issued for acquisition of business
Repurchases of common stock			(253,131)			(253,131)
Accelerated share repurchase			(24,000)
Purchases of common stock upon restricted stock vesting			(7,847)			(7,847)
Net income				258,259		258,259
Dividends				(83,363)		(83,363)
Foreign currency translation adjustments					28,816	28,816
Net unrealized gain (loss) on cash flow hedges, net of tax					5,017	5,017	[1]
Balance, end of year at Aug. 31, 2017	$ 518	$ 741,748	$ (1,606,678)	$ 1,458,823	$ (34,720)	$ 559,691

[1] The unrealized gain (loss) on cash flow hedges disclosed above was net of tax (expense) benefit of ($3,049), $498 and $512 for the fiscal years ended August 31, 2017, 2016 and 2015, respectively.