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Capital Stock (Details) - USD ($) $ / shares in Units, $ in Thousands					1 Months Ended			3 Months Ended		9 Months Ended
	Nov. 05, 2019	Sep. 11, 2019	Jun. 12, 2019	Mar. 13, 2019	Aug. 31, 2019	Apr. 30, 2019	Feb. 28, 2018	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Dividends per Share [Abstract]
Payment of cash dividends										$ 61,636	$ 60,395
Repurchases of Common Stock [Abstract]
Class A common stock repurchased								$ 0	$ 12,399	825	$ 48,222
Amount available for repurchases								$ 470,200		$ 470,200
Treasury Stock [Member]
Repurchases of Common Stock [Abstract]
Class A common stock repurchased (in shares)								0	200,000	14,000	600,000
Class A common stock repurchased								$ 0	$ 12,399	$ 825	$ 48,222
Dividend Declared 2019 Q1 [Member]
Dividends per Share [Abstract]
Dividend payable, date declared								2019-02		2019-02
Dividend payable per share (in dollars per share)							$ 0.37
Payment of cash dividends				$ 20,500
Dividend payable, date paid										Mar. 13, 2019
Dividend payable, date of record										Feb. 25, 2019
Dividend Declared 2019 Q2 [Member]
Dividends per Share [Abstract]
Dividend payable, date declared								2019-04		2019-04
Dividend payable per share (in dollars per share)						$ 0.37
Payment of cash dividends			$ 20,600
Dividend payable, date paid										Jun. 12, 2019
Dividend payable, date of record										May 31, 2019
Dividend Declared 2019 Q3 [Member]
Dividends per Share [Abstract]
Dividend payable, date declared								2019-08		2019-08
Dividend payable per share (in dollars per share)					$ 0.37
Payment of cash dividends		$ 20,600
Dividend payable, date paid										Sep. 11, 2019
Dividend payable, date of record										Aug. 30, 2019
Dividend Declared 2019 Q4 [Member] \| Subsequent Event [Member]
Dividends per Share [Abstract]
Dividend payable, date declared	2019-10
Dividend payable per share (in dollars per share)	$ 0.37
Dividend payable, date paid	Dec. 11, 2019
Dividend payable, date of record	Nov. 29, 2019
Stock Options [Member]
Net Income per Share [Abstract]
Anti-dilutive shares excluded from calculation of diluted earnings per share (in shares)								1,300,000	500,000	1,200,000	900,000