Earnings per Share and Shareholders' Equity Share Repurchase (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	May 31, 2021	May 31, 2020	May 31, 2021	May 31, 2020	Feb. 28, 2021	Aug. 31, 2020	Feb. 29, 2020	Aug. 31, 2019
Equity [Abstract]
Stock Repurchased During Period, Value		$ 17,800		$ 27,500
Treasury Stock, Shares	22,799,230		22,799,230			22,799,230
Stock Repurchase Program, Authorized Amount	$ 667,700		$ 667,700
Stock Repurchase Program, Remaining Number of Shares Authorized to be Repurchased	5,200,770		5,200,770
Stock Repurchased During Period, Shares		839,789		1,343,662
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	$ 416,911	$ 336,282	$ 416,911	$ 336,282	$ 381,393	$ 359,226	$ 354,365	$ 301,179
Net (loss) earnings	25,031	(4,999)	32,811	(716)
Other Comprehensive (Loss) Income, Net of Tax	6,538	(6,586)	17,324	51,289
Stock Issued During Period, Value, Employee Benefit Plan	97	97	279	354
Stock Issued During Period, Value, Restricted Stock Award, Gross	0	0	0	0
APIC, Share-based Payment Arrangement, Increase for Cost Recognition	2,157	3,184	7,384	12,814
Adjustments to Additional Paid in Capital, Income Tax Benefit from Share-based Compensation	(356)	(147)	(2,337)	(4,210)
Stock Value Issued to Acquired For and Distributed From Rabbi Trust	25	83	198	255
Stock Issued During Period, Value, Stock Options Exercised	2,026	0	2,026	2,631
Retained earnings	$ 950,482		$ 950,482			$ 917,671
Treasury Stock, Value, Acquired, Cost Method		$ 9,715		$ 27,520
Stock Repurchased During Period, Shares		839,789		1,343,662
Accounting Standards Update [Domain]
Retained earnings		$ 206		$ 206
Common Stock [Member]
Stock Issued During Period, Shares, New Issues	82,991,000	82,563,000	82,991,000	82,563,000	82,879,000	82,594,000	82,540,000	81,919,000
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	$ 16,598	$ 16,513	$ 16,598	$ 16,513	$ 16,576	$ 16,519	$ 16,508	$ 16,384
Stock Issued During Period, Shares, Employee Benefit Plan	5,000	6,000	15,000	17,000
Stock Issued During Period, Value, Employee Benefit Plan	$ 1	$ 1	$ 3	$ 3
Stock Issued During Period, Shares, Restricted Stock Award, Gross	17,000	13,000	272,000	462,000
Stock Issued During Period, Value, Restricted Stock Award, Gross	$ 3	$ 3	$ 54	$ 93
Stock Issued To Acquired For And Distributed From Rabbi Trust	1,000	4,000	21,000	20,000
Stock Value Issued to Acquired For and Distributed From Rabbi Trust	$ 0	$ 1	$ 4	$ 4
Shares Issued, Shares, Share-based Payment Arrangement, after Forfeiture	89,000	0	89,000	145,000
Stock Issued During Period, Value, Stock Options Exercised	$ 18	$ 0	$ 18	$ 29
Additional Paid-in Capital [Member]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	200,963	192,928	200,963	192,928	197,036	193,492	189,716	181,213
Stock Issued During Period, Value, Employee Benefit Plan	96	96	276	351
Stock Issued During Period, Value, Restricted Stock Award, Gross	(3)	(3)	(54)	(93)
APIC, Share-based Payment Arrangement, Increase for Cost Recognition	2,157	3,184	7,384	12,814
Adjustments to Additional Paid in Capital, Income Tax Benefit from Share-based Compensation	(356)	(147)	(2,337)	(4,210)
Stock Value Issued to Acquired For and Distributed From Rabbi Trust	25	82	194	251
Stock Issued During Period, Value, Stock Options Exercised	2,008	0	2,008	2,602
Treasury Stock [Member]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	(667,732)	(667,732)	(667,732)	(667,732)	(667,732)	(667,732)	(658,017)	(640,212)
Treasury Stock, Value, Acquired, Cost Method		(9,715)		(27,520)
Retained Earnings [Member]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	950,482	918,623	950,482	918,623	925,451	917,671	923,622	915,466
Net (loss) earnings	25,031	(4,999)	32,811	(716)
Retained Earnings [Member] | Accounting Standards Update [Domain]
Retained earnings		3,873		3,873
AOCI Attributable to Parent [Member]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	(83,400)	(124,050)	(83,400)	(124,050)	(89,938)	(100,724)	(117,464)	(171,672)
Other Comprehensive (Loss) Income, Net of Tax	6,538	(6,586)	17,324	51,289
AOCI Attributable to Parent [Member] | Accounting Standards Update [Domain]
Retained earnings		(3,667)		(3,667)
Stock held in trust [member] [Member]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	(2,999)	(2,517)	(2,999)	(2,517)	(2,996)	(2,562)	(2,434)	(3,070)
Stock Value Issued to Acquired For and Distributed From Rabbi Trust	(3)	(83)	(437)	553
Deferred Compensation, Share-based Payments [Member]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	2,999	2,517	2,999	2,517	$ 2,996	$ 2,562	$ 2,434	$ 3,070
Stock Value Issued to Acquired For and Distributed From Rabbi Trust	$ 3	$ 83	$ 437	$ (553)