Earnings per Share and Shareholders' Equity Shareholders' Equity (Details) - USD ($) shares in Thousands	3 Months Ended		9 Months Ended
	May 31, 2020	May 31, 2019	May 31, 2020	May 31, 2019	Feb. 29, 2020	Aug. 31, 2019	Feb. 28, 2019	Aug. 31, 2018
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	$ 336,282,000	$ 607,424,000	$ 336,282,000	$ 607,424,000	$ 354,365,000	$ 301,179,000	$ 585,630,000	$ 558,712,000
Net (loss) earnings	(4,999,000)	32,418,000	(716,000)	17,719,000
Other Comprehensive (Loss) Income, Net of Tax	(6,586,000)	(13,800,000)	51,289,000	20,693,000
Stock Issued During Period, Value, Employee Benefit Plan	97,000	115,000	354,000	359,000
Stock Issued During Period, Value, Restricted Stock Award, Gross	0	0	0	0
Stock Repurchased During Period, Value	9,715,000
Payments for Repurchase of Common Stock	9,700,000		27,520,000	0
APIC, Share-based Payment Arrangement, Increase for Cost Recognition	3,184,000	3,091,000	12,814,000	10,253,000
Stock Issued During Period, Value, Stock Options Exercised	0	206,000	2,631,000	993,000
Adjustments to Additional Paid in Capital, Income Tax Benefit from Share-based Compensation	(147,000)	(322,000)	(4,210,000)	(1,811,000)
Stock Value Issued to Acquired For and Distributed From Rabbi Trust	83,000	86,000	255,000	431,000
Adoption of Accounting Standards	918,623,000		918,623,000			$ 915,466,000
Revision of Prior Period, Accounting Standards Update, Adjustment [Member]
Adoption of Accounting Standards	$ 206,000	$ 75,000	$ 206,000	$ 75,000
Common Stock [Member]
Stock Issued During Period, Shares, New Issues	82,563	81,880	82,563	81,880	82,540	81,919	81,832	81,424
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	$ 16,513,000	$ 16,374,000	$ 16,513,000	$ 16,374,000	$ 16,508,000	$ 16,384,000	$ 16,364,000	$ 16,285,000
Stock Issued During Period, Shares, Employee Benefit Plan	6	5	17	15
Stock Issued During Period, Value, Employee Benefit Plan	$ 1,000	$ 1,000	$ 3,000	$ 3,000
Stock Issued During Period, Shares, Restricted Stock Award, Gross	13	28	462	366
Stock Issued During Period, Value, Restricted Stock Award, Gross	$ 3,000	$ 6,000	$ 93,000	$ 71,000
Shares Issued, Shares, Share-based Payment Arrangement, after Forfeiture	0	10	145	45
Stock Issued During Period, Value, Stock Options Exercised	$ 0	$ 2,000	$ 29,000	$ 9,000
Stock Issued To Acquired For And Distributed From Rabbi Trust	4	5	20	30
Stock Value Issued to Acquired For and Distributed From Rabbi Trust	$ 1,000	$ 1,000	$ 4,000	$ 6,000
Additional Paid-in Capital [Member]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	192,928,000	177,584,000	192,928,000	177,584,000	189,716,000	181,213,000	174,418,000	167,448,000
Stock Issued During Period, Value, Employee Benefit Plan	96,000	114,000	351,000	356,000
Stock Issued During Period, Value, Restricted Stock Award, Gross	(3,000)	(6,000)	(93,000)	(71,000)
APIC, Share-based Payment Arrangement, Increase for Cost Recognition	3,184,000	3,091,000	12,814,000	10,253,000
Stock Issued During Period, Value, Stock Options Exercised	0	204,000	2,602,000	984,000
Adjustments to Additional Paid in Capital, Income Tax Benefit from Share-based Compensation	(147,000)	(322,000)	(4,210,000)	(1,811,000)
Stock Value Issued to Acquired For and Distributed From Rabbi Trust	82,000	85,000	251,000	425,000
Treasury Stock [Member]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	(667,732,000)	(617,731,000)	(667,732,000)	(617,731,000)	(658,017,000)	(640,212,000)	(617,731,000)	(617,731,000)
Stock Repurchased During Period, Value	9,715,000		27,520,000
Retained Earnings [Member]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	918,623,000	1,184,749,000	918,623,000	1,184,749,000	923,622,000	915,466,000	1,152,331,000	1,166,955,000
Net (loss) earnings	(4,999,000)	32,418,000	(716,000)	17,719,000
Retained Earnings [Member] | Revision of Prior Period, Accounting Standards Update, Adjustment [Member]
Adoption of Accounting Standards	3,873,000	75,000	3,873,000	75,000
AOCI Attributable to Parent [Member]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	(124,050,000)	(153,552,000)	(124,050,000)	(153,552,000)	(117,464,000)	(171,672,000)	(139,752,000)	(174,245,000)
Other Comprehensive (Loss) Income, Net of Tax	(6,586,000)	(13,800,000)	51,289,000	20,693,000
AOCI Attributable to Parent [Member] | Revision of Prior Period, Accounting Standards Update, Adjustment [Member]
Adoption of Accounting Standards	(3,667,000)		(3,667,000)
Stock held in trust [member] [Member]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	(2,517,000)	(3,075,000)	(2,517,000)	(3,075,000)	(2,434,000)	(3,070,000)	(2,989,000)	(2,450,000)
Stock Value Issued to Acquired For and Distributed From Rabbi Trust	(83,000)	(86,000)	553,000	(625,000)
Deferred Compensation, Share-based Payments [Member]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	2,517,000	3,075,000	2,517,000	3,075,000	$ 2,434,000	$ 3,070,000	$ 2,989,000	$ 2,450,000
Stock Value Issued to Acquired For and Distributed From Rabbi Trust	$ 83,000	$ 86,000	$ (553,000)	$ 625,000