Consolidated Statements of Changes in Stockholders' Equity - Unaudited - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Treasury Stock	Retained Earnings	Accumulated Other Comprehensive Loss
Beginning balance (in shares) at Aug. 31, 2019		40,104,192		1,986,352
Beginning balance at Aug. 31, 2019	$ 672,256	$ 401	$ 806,973	$ (433,799)	$ 373,225	$ (74,544)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	182,643				182,643
Other comprehensive income (loss)	8,065					8,065
Common stock issued for employee stock plans (in shares)		331,683		43
Common stock issued for employee stock plans	50,480	$ 4	50,487	$ (11)
Vesting of restricted stock (in shares)		16,476		6,209
Vesting of restricted stock	$ (1,575)			$ (1,575)
Repurchase of common stock (in shares)	610,500			610,500
Repurchases of common stock	$ (158,595)			$ (158,595)
Stock-based compensation	18,028		18,028
Dividends declared	(54,542)				(54,542)
Ending balance (in shares) at Feb. 29, 2020		40,452,351		2,603,104
Ending balance at Feb. 29, 2020	716,760	$ 405	875,488	$ (593,980)	501,326	(66,479)
Beginning balance (in shares) at Nov. 30, 2019		40,239,308		2,335,130
Beginning balance at Nov. 30, 2019	691,877	$ 402	835,968	$ (519,678)	439,891	(64,706)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	88,686				88,686
Other comprehensive income (loss)	(1,773)					(1,773)
Common stock issued for employee stock plans (in shares)		211,943		43
Common stock issued for employee stock plans	31,298	$ 3	31,306	$ (11)
Vesting of restricted stock (in shares)		1,100		431
Vesting of restricted stock	$ (119)			$ (119)
Repurchase of common stock (in shares)	267,500			267,500
Repurchases of common stock	$ (74,172)			$ (74,172)
Stock-based compensation	8,214		8,214
Dividends declared	(27,251)				(27,251)
Ending balance (in shares) at Feb. 29, 2020		40,452,351		2,603,104
Ending balance at Feb. 29, 2020	716,760	$ 405	875,488	$ (593,980)	501,326	(66,479)
Beginning balance (in shares) at Aug. 31, 2020		40,767,708		2,737,456
Beginning balance at Aug. 31, 2020	896,375	$ 408	939,067	$ (636,956)	633,149	(39,293)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	197,849				197,849
Other comprehensive income (loss)	10,797					10,797
Common stock issued for employee stock plans (in shares)		157,009		318
Common stock issued for employee stock plans	28,421	$ 1	28,524	$ (104)
Vesting of restricted stock (in shares)		18,943		7,129
Vesting of restricted stock	$ (2,254)			$ (2,254)
Repurchase of common stock (in shares)	353,759			353,759
Repurchases of common stock	$ (114,640)			$ (114,640)
Stock-based compensation	22,327		22,327
Dividends declared	(58,407)				(58,407)
Ending balance (in shares) at Feb. 28, 2021		40,943,660		3,098,662
Ending balance at Feb. 28, 2021	980,468	$ 409	989,918	$ (753,954)	772,591	(28,496)
Beginning balance (in shares) at Nov. 30, 2020		40,884,113		2,875,984
Beginning balance at Nov. 30, 2020	952,573	$ 409	968,375	$ (682,224)	705,089	(39,076)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	96,643				96,643
Other comprehensive income (loss)	10,580					10,580
Common stock issued for employee stock plans (in shares)		58,550		318
Common stock issued for employee stock plans	10,429		10,533	$ (104)
Vesting of restricted stock (in shares)		997		401
Vesting of restricted stock	$ (131)			$ (131)
Repurchase of common stock (in shares)	221,959			221,959
Repurchases of common stock	$ (71,495)			$ (71,495)
Stock-based compensation	11,010		11,010
Dividends declared	(29,141)				(29,141)
Ending balance (in shares) at Feb. 28, 2021		40,943,660		3,098,662
Ending balance at Feb. 28, 2021	$ 980,468	$ 409	$ 989,918	$ (753,954)	$ 772,591	$ (28,496)