Consolidated Statements of Shareholders' Equity - USD ($) $ in Thousands	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Treasury Stock [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]
Beginning balance at Dec. 31, 2015	$ 580,457	$ 448	$ 697,570	$ (2,543,229)	$ 2,692,317	$ (266,649)
Beginning balance, shares at Dec. 31, 2015		27,090,118
Exercise of stock options and restricted stock units, shares		278,623
Exercise of stock options and restricted stock units, Value	(25,471)			(36,450)	(10,979)
Repurchases of Common Stock, Shares		(1,348,507)
Repurchases of Common Stock, Value	(499,992)			(499,992)
Tax benefit resulting from exercise of certain employee stock options	17,680		17,680
Adjustments to Additional Paid in Capital, Share-based Compensation, Other Long-term Incentive Plans, Requisite Service Period Recognition	15,306		15,306
Net earnings	384,370				384,370
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	(88,349)					(88,349)
Ending balance at Dec. 31, 2016	$ 434,943	$ 448	730,556	(3,006,771)	3,065,708	(354,998)
Ending balance, shares at Dec. 31, 2016		26,020,234
Exercise of stock options and restricted stock units, shares	270,413	270,413
Exercise of stock options and restricted stock units, Value	$ (28,649)			(38,586)	(9,937)
Repurchases of Common Stock, Shares	(749,254)	(749,254)
Repurchases of Common Stock, Value	$ (399,997)			(399,997)
Adjustments to Additional Paid in Capital, Share-based Compensation, Other Long-term Incentive Plans, Requisite Service Period Recognition	16,582		16,582
Net earnings	375,972				375,972
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	89,592					89,592
Ending balance at Dec. 31, 2017	$ 547,280	$ 448	747,138	(3,368,182)	3,433,282	(265,406)
Ending balance, shares at Dec. 31, 2017	25,541,393	25,541,393
Cumulative Effect of New Accounting Principle in Period of Adoption	$ 1,539				1,539
Exercise of stock options and restricted stock units, shares	183,379	183,379
Exercise of stock options and restricted stock units, Value	$ (24,600)			(28,577)	(3,977)
Repurchases of Common Stock, Shares	(802,809)	(802,809)
Repurchases of Common Stock, Value	$ (474,999)			(474,999)
Adjustments to Additional Paid in Capital, Share-based Compensation, Other Long-term Incentive Plans, Requisite Service Period Recognition	17,579		17,579
Net earnings	512,611				512,611
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	(37,008)					(37,008)
Ending balance at Dec. 31, 2018	$ 590,063	$ 448	$ 764,717	$ (3,814,604)	$ 3,941,916	$ (302,414)
Ending balance, shares at Dec. 31, 2018	24,921,963	24,921,963