CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (Unaudited) - USD ($) $ in Thousands	Total	Common Stock Member	Additional Paid In Capital Member	Retained Earnings Member	Accumulated Other Comprehensive Loss Member	Treasury Stock Member
Beginning Balance at Dec. 31, 2017		$ 49,187	$ 120,609	$ 1,944,324	$ (216,840)	$ (369,480)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net earnings	$ 192,914
Other Comprehensive Income (Loss), Net of Tax	(21,448)				(21,448)
Dividends paid/declared				(19,798)
Restricted stock			(7,159)			7,159
Stock options exercised			(1,163)			12,298
Other			(725)			725
Share-based compensation			11,631			215
Repurchases of common stock						(78,898)
Ending Balance at Sep. 30, 2018		49,187	123,193	2,115,166	(238,288)	(427,981)
Beginning Balance at Dec. 31, 2017		49,187	120,609	1,944,324	(216,840)	(369,480)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net earnings				192,914
Other Comprehensive Income (Loss), Net of Tax	(71,607)
Ending Balance at Dec. 31, 2018	1,530,781	49,187	118,234	2,191,471	(288,447)	(539,664)
Beginning Balance at Jun. 30, 2018		49,187	119,025	2,047,250	(239,516)	(399,850)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net earnings	74,483			74,483
Other Comprehensive Income (Loss), Net of Tax	1,228				1,228
Dividends paid/declared				(6,567)
Restricted stock			(236)			236
Stock options exercised			372			4,402
Share-based compensation			4,032			14
Repurchases of common stock						(32,783)
Ending Balance at Sep. 30, 2018		49,187	123,193	2,115,166	(238,288)	(427,981)
Cumulative Effect of New Accounting Principle in Period of Adoption | Accounting Standards Update 2014-09 [Member]				(2,274)
Beginning Balance at Dec. 31, 2018	1,530,781	49,187	118,234	2,191,471	(288,447)	(539,664)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net earnings	218,175			218,175
Other Comprehensive Income (Loss), Net of Tax	(11,209)				(11,209)
Dividends paid/declared				(20,947)
Restricted stock			(5,491)			5,491
Stock options exercised			(2,720)			13,662
Other			(661)			661
Share-based compensation			10,857			405
Repurchases of common stock						(37,864)
Ending Balance at Sep. 30, 2019	1,701,140	49,187	120,219	2,414,956	(325,913)	(557,309)
Beginning Balance at Jun. 30, 2019		49,187	116,835	2,339,703	(302,490)	(550,939)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net earnings	82,510			82,510
Other Comprehensive Income (Loss), Net of Tax	(23,423)				(23,423)
Dividends paid/declared				(7,257)
Stock options exercised			(898)			6,429
Share-based compensation			4,282			0
Repurchases of common stock						(12,799)
Ending Balance at Sep. 30, 2019	$ 1,701,140	$ 49,187	$ 120,219	2,414,956	(325,913)	$ (557,309)
Cumulative Effect of New Accounting Principle in Period of Adoption | Accounting Standards Update 2018-02 [Member]				$ 26,257	$ (26,257)