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Capital Stock (Details) - USD ($) $ / shares in Units, $ in Thousands				1 Months Ended				3 Months Ended		9 Months Ended
	Sep. 09, 2020	Jun. 10, 2020	Mar. 11, 2020	Oct. 30, 2020	Jul. 31, 2020	Apr. 30, 2020	Feb. 29, 2020	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Dividends per Share [Abstract]
Payment of cash dividends										$ 59,287	$ 61,636
Repurchases of Common Stock [Abstract]
Class A common stock repurchased								$ 19,994	$ 0	127,361	$ 825
Amount available for repurchases								$ 342,800		$ 342,800
Treasury Stock [Member]
Repurchases of Common Stock [Abstract]
Class A common stock repurchased (in shares)								400,000	0	4,800,000	14,000
Class A common stock repurchased								$ 19,994	$ 0	$ 127,361	$ 825
Dividend Declared 2020-Q1 [Member]
Dividends per Share [Abstract]
Dividend payable, date declared								2020-02		2020-02
Dividend payable per share (in dollars per share)							$ 0.375
Payment of cash dividends			$ 20,700
Dividend payable, date paid										Mar. 11, 2020
Dividend payable, date of record										Feb. 28, 2020
Dividend Declared 2020-Q2 [Member]
Dividends per Share [Abstract]
Dividend payable, date declared								2020-04		2020-04
Dividend payable per share (in dollars per share)						$ 0.375
Payment of cash dividends		$ 19,400
Dividend payable, date paid										Jun. 10, 2020
Dividend payable, date of record										May 29, 2020
Dividend Declared 2020-Q3 [Member]
Dividends per Share [Abstract]
Dividend payable, date declared								2020-07		2020-07
Dividend payable per share (in dollars per share)					$ 0.375
Payment of cash dividends	$ 19,200
Dividend payable, date paid										Sep. 09, 2020
Dividend payable, date of record										Aug. 28, 2020
Dividend Declared 2020-Q4 [Member] \| Subsequent Event [Member]
Dividends per Share [Abstract]
Dividend payable, date declared				2020-10
Dividend payable per share (in dollars per share)				$ 0.375
Dividend payable, date paid				Dec. 09, 2020
Dividend payable, date of record				Nov. 27, 2020
Stock Options [Member]
Net Income per Share [Abstract]
Anti-dilutive shares excluded from calculation of diluted earnings per share (in shares)								200,000	1,300,000	600,000	1,200,000