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 Income (Loss) Member	Treasury Stock Member
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Accumulated other comprehensive loss	$ (216,840)
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				275,749
Other comprehensive income, net of tax	(71,607)				(71,607)
Dividends paid/declared				(26,328)
Restricted stock			(13,134)			13,134
Stock options exercised			(2,355)			14,294
Share-based compensation			13,866			228
Repurchases of common stock						(198,592)
Other			(752)			752
Ending Balance at Dec. 31, 2018	1,530,781	49,187	118,234	2,191,471	(288,447)	(539,664)
Retained earnings	2,191,471
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative Effect of New Accounting Principle in Period of Adoption | Accounting Standards Update 2014-09 [Member]				(2,274)
Accumulated other comprehensive loss	(288,447)
Net earnings	55,593			55,593
Other comprehensive income, net of tax	9,925				9,925
Dividends paid/declared				(6,419)
Restricted stock			(5,491)			5,491
Stock options exercised			(519)			5,195
Share-based compensation			3,133			362
Repurchases of common stock						(12,471)
Other			(661)			661
Ending Balance at Mar. 31, 2019	1,585,580	$ 49,187	$ 114,696	$ 2,266,902	$ (304,779)	$ (540,426)
Retained earnings	2,266,902
Retained earnings | Accounting Standards Update 2018-02 [Member]	26,257
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Accumulated other comprehensive loss	(304,779)
Accumulated other comprehensive loss | Accounting Standards Update 2018-02 [Member]	$ (26,257)