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, 2013	$ 935,052	$ 448	$ 653,250	$ (1,721,030)	$ 2,037,420	$ (35,036)
Beginning balance, shares at Dec. 31, 2013		29,487,075
Stock Issued During Period, Value, Treasury Stock Reissued	21,047			39,374	(18,327)
Exercise of stock options and restricted stock units, shares		373,431
Repurchases of common stock	(414,000)			(414,000)
Repurchases of common stock, shares		(1,617,499)
Tax benefit resulting from exercise of certain employee stock options	3,557		3,557
Adjustment to Additional Paid in Capital, Share-Based Compensation	13,611		13,611
Net Income (Loss) Attributable to Parent	338,241				338,241
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	(177,913)					(177,913)
Ending balance at Dec. 31, 2014	719,595	448	670,418	(2,095,656)	2,357,334	(212,949)
Ending balance, shares at Dec. 31, 2014	28,243,007	28,243,007
Stock Issued During Period, Value, Treasury Stock Reissued	9,546			14,129	(4,583)
Exercise of stock options and restricted stock units, shares	125,398	125,398
Repurchases of common stock	(123,745)			(123,745)
Repurchases of common stock, shares	(400,845)	(400,845)
Tax benefit resulting from exercise of certain employee stock options	441		441
Adjustment to Additional Paid in Capital, Share-Based Compensation	3,496		3,496
Net Income (Loss) Attributable to Parent	63,051				63,051
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	(6,256)					(6,256)
Ending balance at Mar. 31, 2015	$ 666,128	$ 448	$ 674,355	$ (2,205,272)	$ 2,415,802	$ (219,205)
Ending balance, shares at Mar. 31, 2015	27,967,560	27,967,560