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, 2010	$ 771,584	$ 448	$ 597,195	$ (1,057,390)	$ 1,223,130	$ 8,201
Beginning balance, shares at Dec. 31, 2010		32,425,315
Stock Issued During Period, Value, Treasury Stock Reissued	20,770			36,843	(16,073)
Exercise of stock options and restricted stock units, shares		450,613
Other treasury stock issuances	(204,578)
Repurchases of common stock				(204,578)
Repurchases of common stock, shares		(1,285,827)
Tax benefit resulting from exercise of certain employee stock options	6,737		6,737
Adjustment to Additional Paid in Capital, Share-Based Compensation	12,270		12,270
Net earnings	269,493				269,493
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	(95,139)					(95,139)
Ending balance at Dec. 31, 2011	781,137	448	616,202	(1,225,125)	1,476,550	(86,938)
Ending balance, shares at Dec. 31, 2011	31,590,101	31,590,101
Stock Issued During Period, Value, Treasury Stock Reissued	13,264			19,771	(6,507)
Exercise of stock options and restricted stock units, shares	233,146	233,146
Other treasury stock issuances	(135,766)
Repurchases of common stock	(135,800)			(135,766)
Repurchases of common stock, shares	(797,095)	(797,095)
Tax benefit resulting from exercise of certain employee stock options	298		298
Adjustment to Additional Paid in Capital, Share-Based Compensation	5,954		5,954
Net earnings	114,031				114,031
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	(3,944)					(3,944)
Ending balance at Jun. 30, 2012	$ 774,974	$ 448	$ 622,454	$ (1,341,120)	$ 1,584,074	$ (90,882)
Ending balance, shares at Jun. 30, 2012	31,026,152	31,026,152