Consolidated Statement of Equity - USD ($) $ in Thousands	Total	Adjustments for New Accounting Pronouncement	Common Stock	Common Stock Adjustments for New Accounting Pronouncement	Treasury Stock	Treasury Stock Adjustments for New Accounting Pronouncement	Capital in Excess of Par Value	Capital in Excess of Par Value Adjustments for New Accounting Pronouncement	Retained Earnings [Member]	Retained Earnings [Member] Adjustments for New Accounting Pronouncement	Accumulated Other Comprehensive Income	Accumulated Other Comprehensive Income Adjustments for New Accounting Pronouncement	Noncontrolling Interest	Noncontrolling Interest Adjustments for New Accounting Pronouncement
Balance at beginning of period at Dec. 31, 2018	$ 1,641,815		$ 184,721		$ (3,250)		$ 972,710		$ 474,327		$ 13,395		$ (88)
Stockholders' Equity Attributable to Noncontrolling Interest [Roll Forward]
Comprehensive income	86,614		0		0		0		79,323		7,251		40
Dividends, Common Stock	(32,820)		0		0		0		32,820		0		0
Stock option exercises	15,962		950		0		15,012		0		0		0
Restricted stock awards, net of forfeitures	0		126		0		(126)		0		0		0
Employee share-based compensation earned	4,568		0		0		4,568		0		0		0
Purchase of Company common stock	(14,542)		0		(355)		(1,935)		(12,252)		0		0
Other	(1,192)		59		0		(1,251)		0		0		0
Balance at end of period at Mar. 31, 2019	1,700,405		185,856		(3,605)		988,978		508,578		20,646		(48)
Balance at beginning of period at Dec. 31, 2018	1,641,815		184,721		(3,250)		972,710		474,327		13,395		(88)
Stockholders' Equity Attributable to Noncontrolling Interest [Roll Forward]
Comprehensive income	232,731
Balance at end of period at Sep. 30, 2019	1,775,520		187,257		(4,426)		1,015,525		553,610		23,527		27
Stockholders' Equity Attributable to Noncontrolling Interest [Roll Forward]
Payments of Debt Issuance Costs	15,537
Balance at beginning of period at Mar. 31, 2019	1,700,405		185,856		(3,605)		988,978		508,578		20,646		(48)
Stockholders' Equity Attributable to Noncontrolling Interest [Roll Forward]
Comprehensive income	79,511		0		0		0		72,329		7,146		36
Dividends, Common Stock	(32,871)		0		0		0		(32,871)		0		0
Stock option exercises	7,139		513		0		6,626		0		0		0
Employee share-based compensation earned	3,445		0		0		3,445		0		0		0
Purchase of Company common stock	(15,032)		0		(337)		(1,832)		(12,863)		0		0
Other	1,619		42		0		1,577		0		0		0
Balance at end of period at Jun. 30, 2019	1,744,216		186,411		(3,942)		998,794		535,173		27,792		(12)
Stockholders' Equity Attributable to Noncontrolling Interest [Roll Forward]
Comprehensive income	66,606		0		0		0		70,792		(4,265)		79
Dividends, Common Stock	$ (32,890)		0		0		0		(32,890)		0		0
Dividends declared per share	$ 180
Stock option exercises	$ 16,730		844		0		15,886		0		0		0
Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders	(40)		0		0				0		0		(40)
Employee share-based compensation earned	3,550		0		0		3,550		0		0		0
Purchase of Company common stock	(22,609)		0		(484)		(2,660)		(19,465)		0		0
Other	(43)		2		0		(45)		0		0		0
Balance at end of period at Sep. 30, 2019	1,775,520		187,257		(4,426)		1,015,525		553,610		23,527		27
Balance at beginning of period at Dec. 31, 2019	1,823,255		185,101		(3,916)		1,010,361		601,903		29,864		(58)
Stockholders' Equity Attributable to Noncontrolling Interest [Roll Forward]
Comprehensive income	50,799		0		0		0		81,941		(31,200)		58
Dividends, Common Stock	(34,414)		0		0		0		(34,414)		0		0
Stock option exercises	15,126		789		0		14,337		0		0		0
Restricted stock awards, net of forfeitures	0		168		0		(168)		0		0		0
Employee share-based compensation earned	3,406		0		0		3,406		0		0		0
Purchase of Company common stock	(123,102)		0		(2,901)		(16,202)		(103,999)		0		0
Other	(1,095)		0		0		(1,095)		0		0		0
Balance at end of period at Mar. 31, 2020	1,751,093		186,058		(6,817)		1,010,639		562,549		(1,336)		0
Stockholders' Equity Attributable to Noncontrolling Interest [Roll Forward]
Stockholders' Equity, Period Increase (Decrease)		$ 17,118		$ 0		$ 0		$ 0		$ 17,118		$ 0		$ 0
Balance at beginning of period at Dec. 31, 2019	1,823,255		185,101		(3,916)		1,010,361		601,903		29,864		(58)
Stockholders' Equity Attributable to Noncontrolling Interest [Roll Forward]
Comprehensive income	305,452
Balance at end of period at Sep. 30, 2020	1,743,136		186,186		(11,951)		992,072		556,495		20,270		64
Stockholders' Equity Attributable to Noncontrolling Interest [Roll Forward]
Payments of Debt Issuance Costs	14,501
Balance at beginning of period at Mar. 31, 2020	1,751,093		186,058		(6,817)		1,010,639		562,549		(1,336)		0
Stockholders' Equity Attributable to Noncontrolling Interest [Roll Forward]
Comprehensive income	119,291		0		0		0		105,508		13,736		47
Dividends, Common Stock	$ (33,719)		0		0		0		(33,719)		0		0
Dividends declared per share
Employee share-based compensation earned	$ 3,638		0		0		3,638		0		0		0
Purchase of Company common stock	(87,466)		0		(2,277)		(12,862)		(72,327)		0		0
Other	1,620		47		0		1,573		0		0		0
Balance at end of period at Jun. 30, 2020	1,754,328		186,105		(9,094)		1,002,988		561,882		12,400		47
Stockholders' Equity Attributable to Noncontrolling Interest [Roll Forward]
Stockholders' Equity, Period Increase (Decrease)		$ (129)		$ 0		$ 0		$ 0		$ (129)		$ 0		$ 0
Comprehensive income	135,362		0		0		0		127,415		7,870		77
Dividends, Common Stock	$ (33,339)		0		0		0		(33,339)		0		0
Dividends declared per share	$ 190
Stock option exercises	$ 1,873		82		0		1,791		0		0		0
Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders	(60)		0		0		0		0		0		(60)
Restricted stock awards, net of forfeitures	0		2		0		(2)		0		0		0
Employee share-based compensation earned	3,527		0		0		3,527		0		0		0
Purchase of Company common stock	(118,555)		0		(2,857)		(16,235)		(99,463)		0		0
Other	0		(3)		0		3		0		0		0
Balance at end of period at Sep. 30, 2020	$ 1,743,136		$ 186,186		$ (11,951)		$ 992,072		$ 556,495		$ 20,270		$ 64