Condensed Consolidated Statements of Changes in Shareholders' Equity (USD $) In Thousands	Total	Common Stock	Additional Paid-in Capital	Retained Earnings	Accumulated Other Comprehensive Income (Loss)	Treasury Stock
Beginning Balance at Dec. 31, 2010	$ 583,195	$ 471	$ 302,911	$ 265,676	$ 15,108	$ (971)
Beginning Balance, shares at Dec. 31, 2010		47,066
Issuance of common stock	191		191
Stock-based compensation expense	3,411		3,411
Excess tax benefit (deficiency) from stock-based compensation	(52)		(52)
Vesting of common stock and restricted stock under equity award plans, net of forfeitures	(1,190)	3	(992)			(201)
Vesting of common stock and restricted stock under equity award plans, shares		312
Repurchase of common stock	(42,677)					(42,677)
Retirement of treasury stock		(28)	(22,359)	(20,290)		42,677
Retirement of treasury stock, shares		(2,798)
Comprehensive income (loss)	32,704			43,263	(10,559)
Ending Balance at Sep. 30, 2011	575,582	446	283,110	288,649	4,549	(1,172)
Ending Balance, shares at Sep. 30, 2011		44,580
Issuance of common stock	120		120
Issuance of common stock, shares		33
Stock-based compensation expense	171		171
Excess tax benefit (deficiency) from stock-based compensation	44		44
Vesting of common stock and restricted stock under equity award plans, net of forfeitures			13			(13)
Vesting of common stock and restricted stock under equity award plans, shares		(19)
Repurchase of common stock	(7,316)					(7,316)
Retirement of treasury stock		(3)	(2,301)	(1,924)		4,228
Retirement of treasury stock, shares		(288)
Comprehensive income (loss)	4,965			5,078	(113)
Ending Balance at Dec. 31, 2011	573,566	443	281,157	291,803	4,436	(4,273)
Ending Balance, shares at Dec. 31, 2011		44,306
Stock-based compensation expense	3,111		3,111
Excess tax benefit (deficiency) from stock-based compensation	(278)		(278)
Vesting of common stock and restricted stock under equity award plans, net of forfeitures	(1,412)	3	(1,224)			(191)
Vesting of common stock and restricted stock under equity award plans, shares		227
Repurchase of common stock	(7,908)					(7,908)
Retirement of treasury stock		(8)	(5,945)	(5,039)		10,992
Retirement of treasury stock, shares		(745)
Comprehensive income (loss)	24,509			15,133	9,376
Ending Balance at Sep. 30, 2012	$ 591,588	$ 438	$ 276,821	$ 301,897	$ 13,812	$ (1,380)
Ending Balance, shares at Sep. 30, 2012		43,788