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, 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 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
Stockholders' Equity Attributable to Noncontrolling Interest [Roll Forward]
Cumulative Effect of New Accounting Principle in Period of Adoption	$ 17,118	$ 0	$ 0	$ 0	$ 17,118	$ 0	$ 0