Consolidated Statements of Changes in Stockholders' Equity (Unaudited) - USD ($) $ in Thousands		Common Stock [Member]	Additional Paid-in Capital [Member]	Treasury Stock [Member]	Retained Earnings [Member]	AOCI Attributable to Parent [Member]	Total
Balance (in shares) at Aug. 31, 2017		51,845,132		12,822,100
Balance at Aug. 31, 2017		$ 518	$ 741,748	$ (1,606,678)	$ 1,458,823	$ (34,720)	$ 559,691
Net income					198,262		198,262
Other comprehensive (loss) income						(6,365)	(6,365)
Common stock issued for employee stock plans (in shares)		557,075		106
Common stock issued for employee stock plans		$ 6	64,634	$ (19)			64,621
Vesting of restricted stock (in shares)		15,063		5,563
Vesting of restricted stock				$ (1,014)			$ (1,014)
Repurchases of common stock (in shares)				1,204,920			1,204,920
Repurchases of common stock				$ (234,836)			$ (234,836)
Stock-based compensation expense			23,241				23,241
Dividends declared					(68,267)		(68,267)
Retirement of treasury shares (in shares)		(13,292,689)		(13,292,689)
Retirement of treasury shares		$ (133)	(186,717)	$ 1,697,205	(1,510,355)
Balance (in shares) at May. 31, 2018		39,124,581		740,000
Balance at May. 31, 2018		$ 391	642,906	$ (145,342)	78,463	(41,085)	535,333
Balance (in shares) at Feb. 28, 2018		39,047,153		120,000
Balance at Feb. 28, 2018		$ 390	625,394	$ (23,379)	28,283	(18,598)	612,090
Net income					74,746		74,746
Other comprehensive (loss) income						(22,487)	(22,487)
Common stock issued for employee stock plans (in shares)		77,204
Common stock issued for employee stock plans		$ 1	9,691				9,692
Vesting of restricted stock (in shares)		224
Vesting of restricted stock
Repurchases of common stock (in shares)				620,000			620,000
Repurchases of common stock				$ (121,963)			$ (121,963)
Stock-based compensation expense			7,821				7,821
Dividends declared					(24,566)		(24,566)
Retirement of treasury shares (in shares)
Retirement of treasury shares
Balance (in shares) at May. 31, 2018		39,124,581		740,000
Balance at May. 31, 2018		$ 391	642,906	$ (145,342)	78,463	(41,085)	535,333
Balance (in shares) at Aug. 31, 2018		39,264,849		1,072,263
Balance at Aug. 31, 2018		$ 393	667,531	$ (213,428)	122,843	(51,439)	525,900
Net income					261,263		261,263
Other comprehensive (loss) income						(14,399)	(14,399)
Common stock issued for employee stock plans (in shares)		642,444
Common stock issued for employee stock plans		$ 7	90,039				90,046
Vesting of restricted stock (in shares)		75,530		27,852
Vesting of restricted stock				$ (6,155)			$ (6,155)
Repurchases of common stock (in shares)				664,945			664,945
Repurchases of common stock				$ (152,139)			$ (152,139)
Stock-based compensation expense			24,135				24,135
Dividends declared					(76,263)		(76,263)
Cumulative effect of adoption of accounting standards*	[1]				1,304	717	2,021
Balance (in shares) at May. 31, 2019		39,982,823		1,765,060
Balance at May. 31, 2019		$ 400	781,705	$ (371,722)	309,147	(65,121)	654,409
Balance (in shares) at Feb. 28, 2019		39,690,225		1,590,060
Balance at Feb. 28, 2019		$ 397	732,538	$ (324,167)	244,388	(53,635)	599,521
Net income					92,265		92,265
Other comprehensive (loss) income						(11,486)	(11,486)
Common stock issued for employee stock plans (in shares)		292,598
Common stock issued for employee stock plans		$ 3	41,172				41,175
Vesting of restricted stock (in shares)
Vesting of restricted stock
Repurchases of common stock (in shares)				175,000			175,000
Repurchases of common stock				$ (47,555)			$ (47,555)
Stock-based compensation expense			7,995				7,995
Dividends declared					(27,506)		(27,506)
Balance (in shares) at May. 31, 2019		39,982,823		1,765,060
Balance at May. 31, 2019		$ 400	$ 781,705	$ (371,722)	$ 309,147	$ (65,121)	$ 654,409

[1] Includes the cumulative effect of adoption of accounting standards primarily due to both the adoption of the new revenue recognition standard (ASC 606) resulting in a cumulative increase to retained earnings related to certain fulfillment costs and the accounting standard update related to the U.S. Tax Cuts and Jobs Act ("TCJA") providing for the reclassification from accumulated other comprehensive loss to retained earnings for stranded tax effects. See Notes 3 and 4 for additional information.