Consolidated Statements Of Shareholders' Equity (USD $) In Thousands, except Share data	Common Shares [Member]	Additional Paid-In Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Loss [Member]	Treasury Shares [Member]	Total
Balances, value at Dec. 31, 2009	$ 6,410	$ 732,956	$ 356,288	$ (4,993)	$ (272)	$ 1,090,389
Balances, shares at Dec. 31, 2009	64,097,000
Stock-based compensation expense		5,415				5,415
Shares repurchased and retired, shares	(3,320,000)
Shares repurchased and retired, value	(332)	(35,689)	(22,834)			(58,855)
Stock options exercised, shares	290,000					290,000
Stock options exercised, value	29	3,223				3,252
Issuance of restricted shares, net of forfeitures, shares	18,000
Issuance of restricted shares, net of forfeitures, value	2	(2)
Excess tax benefit of stock-based compensation		1,235				1,235
Comprehensive income			79,758	(1,969)		77,789
Balances, value at Dec. 31, 2010	6,109	707,138	413,212	(6,962)	(272)	1,119,225
Balances, shares at Dec. 31, 2010	61,085,000
Stock-based compensation expense		5,097				5,097
Shares repurchased and retired, shares	(3,715,000)
Shares repurchased and retired, value	(372)	(39,931)	(15,978)			(56,281)
Stock options exercised, shares	257,000					257,000
Stock options exercised, value	26	2,545				2,571
Issuance of restricted shares, net of forfeitures, shares	164,000
Issuance of restricted shares, net of forfeitures, value	16	(16)
Excess tax benefit of stock-based compensation		(335)				(335)
Comprehensive income			51,959	(6,488)		45,471
Balances, value at Dec. 31, 2011	5,779	674,498	449,193	(13,450)	(272)	1,115,748
Balances, shares at Dec. 31, 2011	57,791,000					57,791,000
Stock-based compensation expense		6,270				6,270
Shares repurchased and retired, shares	(3,224,000)
Shares repurchased and retired, value	(322)	(34,650)	(12,134)			(47,106)
Stock options exercised, shares	375,000					375,000
Stock options exercised, value	38	4,619				4,657
Issuance of restricted shares, net of forfeitures, shares	244,000
Issuance of restricted shares, net of forfeitures, value	24	(24)
Excess tax benefit of stock-based compensation		435				435
Comprehensive income			56,607	2,914		59,521
Balances, value at Dec. 31, 2012	$ 5,519	$ 651,148	$ 493,666	$ (10,536)	$ (272)	$ 1,139,525
Balances, shares at Dec. 31, 2012	55,186,000					55,186,000