Condensed Consolidated Statement of Changes in Stockholder's Equity - USD ($) $ in Thousands	Common Stock	Treasury Stock	Additional Paid-In Capital	Retained Earnings Cumulative Effect, Period of Adoption, Adjustment	Retained Earnings	Accumulated Other Comprehensive Income (loss), net	Redeemable Noncontrolling Interests	Cumulative Effect, Period of Adoption, Adjustment	Total
Beginning balance at Dec. 31, 2018	$ 1,200	$ (720,100)	$ 2,660,200		$ 1,288,200	$ 11,500	$ 9,400		$ 3,241,000
Increase (Decrease) in Stockholders' Equity
Cash dividends on common stock					(34,800)				(34,800)
Stock-based compensation			5,400						5,400
Exercise of common stock options			8,100						8,100
Repurchases of common stock from employee stock plans		(10,000)							(10,000)
Purchase of common stock		(35,000)							(35,000)
Shares issued under employee stock purchase plan		800							800
Net income excluding noncontrolling interest					95,400				95,400
Other comprehensive (loss) income						14,700			14,700
Net loss attributable to redeemable noncontrolling interest							(200)
Redemption value adjustment of redeemable noncontrolling interest					(200)		200		(200)
Ending balance at Mar. 31, 2019	1,200	(764,300)	2,673,700		1,348,600	26,200	9,400		3,285,400
Beginning balance at Dec. 31, 2018	1,200	(720,100)	2,660,200		1,288,200	11,500	9,400		3,241,000
Increase (Decrease) in Stockholders' Equity
Net income									288,600
Ending balance at Sep. 30, 2019	1,200	(817,300)	2,686,500		1,467,400	(9,100)			3,328,700
Beginning balance at Mar. 31, 2019	1,200	(764,300)	2,673,700		1,348,600	26,200	9,400		3,285,400
Increase (Decrease) in Stockholders' Equity
Cash dividends on common stock					(34,800)				(34,800)
Stock-based compensation			6,300						6,300
Exercise of common stock options			400						400
Repurchases of common stock from employee stock plans		(400)							(400)
Shares issued under employee stock purchase plan		100							100
Net income					88,300				88,300
Other comprehensive (loss) income						(18,100)			(18,100)
Net loss attributable to redeemable noncontrolling interest							(3,800)
Redemption value adjustment of redeemable noncontrolling interest					(200)		200		(200)
Ending balance at Jun. 30, 2019	1,200	(764,600)	2,680,400		1,401,900	8,100	5,800		3,327,000
Increase (Decrease) in Stockholders' Equity
Cash dividends on common stock					(40,400)				(40,400)
Stock-based compensation			5,300						5,300
Exercise of common stock options			800						800
Repurchases of common stock from employee stock plans		(300)							(300)
Purchase of common stock		(52,400)							(52,400)
Net income									106,000
Net income excluding noncontrolling interest					106,000				106,000
Other comprehensive (loss) income						(17,200)			(17,200)
Net loss attributable to redeemable noncontrolling interest							(100)
Redemption value adjustment of redeemable noncontrolling interest					(100)		100		(100)
Deconsolidation of former subsidiary with noncontrolling interest							$ (5,800)
Ending balance at Sep. 30, 2019	1,200	(817,300)	2,686,500		1,467,400	(9,100)			3,328,700
Beginning balance at Dec. 31, 2019	1,200	(887,100)	2,691,300	$ (400)	1,512,600	37,600		$ (400)	3,355,600
Increase (Decrease) in Stockholders' Equity
Cash dividends on common stock					(40,000)				(40,000)
Stock-based compensation			8,300						8,300
Repurchases of common stock from employee stock plans		(13,900)							(13,900)
Purchase of common stock		(119,500)							(119,500)
Shares issued under employee stock purchase plan			100						100
Net income					157,400				157,400
Other comprehensive (loss) income						(37,500)			(37,500)
Ending balance at Mar. 31, 2020	1,200	(1,020,500)	2,699,700		1,629,600	100			3,310,100
Beginning balance at Dec. 31, 2019	1,200	(887,100)	2,691,300	$ (400)	1,512,600	37,600		$ (400)	3,355,600
Increase (Decrease) in Stockholders' Equity
Net income									380,900
Other comprehensive (loss) income						(8,600)
Ending balance at Sep. 30, 2020	1,200	(1,162,400)	2,708,900		1,767,800	29,000			3,344,500
Beginning balance at Mar. 31, 2020	1,200	(1,020,500)	2,699,700		1,629,600	100			3,310,100
Increase (Decrease) in Stockholders' Equity
Cash dividends on common stock					(39,500)				(39,500)
Stock-based compensation			4,600						4,600
Exercise of common stock options			200						200
Repurchases of common stock from employee stock plans		(200)							(200)
Purchase of common stock		(99,800)							(99,800)
Net income					113,600				113,600
Other comprehensive (loss) income						(2,700)			(2,700)
Ending balance at Jun. 30, 2020	1,200	(1,120,500)	2,704,500		1,703,700	(2,600)			3,286,300
Increase (Decrease) in Stockholders' Equity
Cash dividends on common stock					(45,800)				(45,800)
Stock-based compensation			4,400						4,400
Repurchases of common stock from employee stock plans		(100)							(100)
Purchase of common stock		(41,800)							(41,800)
Net income					109,900				109,900
Other comprehensive (loss) income						31,600			31,600
Ending balance at Sep. 30, 2020	$ 1,200	$ (1,162,400)	$ 2,708,900		$ 1,767,800	$ 29,000			$ 3,344,500