Shareholders' Equity (Details) - USD ($) $ / shares in Units, $ in Thousands		1 Months Ended			12 Months Ended
	Oct. 20, 2020	Nov. 30, 2018	Oct. 31, 2018	Sep. 30, 2018	Aug. 29, 2020	Aug. 31, 2019	Sep. 01, 2018
Components Of Shareholders Equity [Line Items]
Repurchase and retirement of common stock, Shares						8,212,000
Repurchase and retirement of common stock, Value						$ 493,612
Purchase of treasury stock						$ 84,611
Shares repurchased						44,000
Preferred stock, shares authorized					5,000,000	5,000,000
Preferred stock, shares issued					0	0
Preferred stock, shares outstanding					0	0
Subsequent Event [Member]
Components Of Shareholders Equity [Line Items]
Dividends declared date	Oct. 20, 2020
Dividends payable per share	$ 0.75
Dividend payable date	Nov. 24, 2020
Dividends record date	Nov. 10, 2020
Dividend payable amount	$ 41,706
Class A Common Stock [Member]
Components Of Shareholders Equity [Line Items]
Repurchase and retirement of common stock, Shares		123,000	2,000	113,000
Cost of repurchase, per share		$ 81.22	$ 85.00	$ 84.29
Common stock, votes per share					one
Class B Common Stock [Member]
Components Of Shareholders Equity [Line Items]
Common stock, votes per share					10
Treasury Stock [Member]
Components Of Shareholders Equity [Line Items]
Common stock shares repurchased						1,055,000
Treasury stock repurchased, and treasury stock repurchased and retired, shares					48,000
Treasury stock repurchased, and treasury stock repurchased and retired, amount					$ 3,444
Number of shares authorized for repurchase					5,000,000
Maximum number of shares that can be repurchased					1,157,000
Treasury stock reissued to fund plan, shares					69,000	64,000
Treasury Stock [Member] | Class A Common Stock [Member]
Components Of Shareholders Equity [Line Items]
Purchase of treasury stock					$ 3,444	$ 24,284	$ 25,432