Interim Consolidated Statements of Shareholders' Equity and Comprehensive Income (Unaudited) (USD $) In Thousands, except Share data	Total	Common Stock	Additional Paid-in Capital	Treasury Stock	Retained Earnings	Accumulated Other Comprehensive Income (Loss)
Beginning balance at Dec. 31, 2012	$ 827,219	$ 448	$ 638,705	$ (1,463,924)	$ 1,749,451	$ (97,461)
Beginning balance, shares at Dec. 31, 2012		30,410,006
Stock Issued During Period, Value, Treasury Stock Reissued	19,745			37,870	(18,125)
Exercise of stock options and restricted stock units, shares		398,646
Repurchases of common stock	(294,976)			(294,976)
Repurchases of common stock, shares		(1,321,577)
Tax benefit resulting from exercise of certain employee stock options	1,906		1,906
Adjustment to Additional Paid in Capital, Share-Based Compensation	12,639		12,639
Net Income (Loss) Attributable to Parent	306,094				306,094
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	62,425					62,425
Ending balance at Dec. 31, 2013	935,052	448	653,250	(1,721,030)	2,037,420	(35,036)
Ending balance, shares at Dec. 31, 2013	29,487,075	29,487,075
Stock Issued During Period, Value, Treasury Stock Reissued	3,450			6,978	(3,528)
Exercise of stock options and restricted stock units, shares	69,442	69,442
Repurchases of common stock	(82,498)			(82,498)
Repurchases of common stock, shares	(336,188)	(336,188)
Tax benefit resulting from exercise of certain employee stock options	4,495		4,495
Adjustment to Additional Paid in Capital, Share-Based Compensation	3,201		3,201
Net Income (Loss) Attributable to Parent	58,051				58,051
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	1,853					1,853
Ending balance at Mar. 31, 2014	$ 923,604	$ 448	$ 660,946	$ (1,796,550)	$ 2,091,943	$ (33,183)
Ending balance, shares at Mar. 31, 2014	29,220,329	29,220,329