Consolidated Statement of Equity - USD ($) $ in Thousands	Total	Common Stock	Treasury Stock	Capital in Excess of Par Value	Retained Earnings [Member]	Accumulated Other Comprehensive Income	Noncontrolling Interest
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 declared on 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	166,125
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]
Payments of Debt Issuance Costs	15,536
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 declared per share	$ 180
Dividends declared on 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)
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 declared per share
Dividends declared on 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
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	170,090
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]
Payments of Debt Issuance Costs	0
New Accounting Pronouncement or Change in Accounting Principle, Cumulative Effect of Change on Equity or Net Assets	17,118	0	0	0	17,118	0	0
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 declared per share	$ 190
Dividends declared on common stock	$ (33,719)	0	0	0	(33,719)	0	0
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]
New Accounting Pronouncement or Change in Accounting Principle, Cumulative Effect of Change on Equity or Net Assets	$ 17,000	$ 0	$ 0	$ 0	$ (129)	$ 0	$ 0