Condensed Consolidated Statements of Changes in Shareholders' Equity (Unaudited) (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
Stock-based compensation expense	1,750		1,750
Excess tax benefit (deficiency) from stock-based compensation	32		32
Vesting of common stock and restricted stock under equity award plans	(1,190)	3	(1,070)			(123)
Vesting of common stock and restricted stock under equity award plans, shares		264
Repurchase of common stock	(5,512)					(5,512)
Retirement of treasury stock		(3)	(2,400)	(3,109)		5,512
Retirement of treasury stock, shares		(300)
Comprehensive income (loss)	19,188			13,178	6,010
Ending Balance at Mar. 31, 2011	597,463	471	301,223	275,745	21,118	(1,094)
Ending Balance, shares at Mar. 31, 2011		47,030
Issuance of common stock	311		311
Issuance of common stock, shares		33
Stock-based compensation expense	1,832		1,832
Excess tax benefit (deficiency) from stock-based compensation	(40)		(40)
Vesting of common stock and restricted stock under equity award plans			91			(91)
Vesting of common stock and restricted stock under equity award plans, shares		29
Repurchase of common stock	(44,481)					(44,481)
Retirement of treasury stock		(28)	(22,260)	(19,105)		41,393
Retirement of treasury stock, shares		(2,786)
Comprehensive income (loss)	18,481			35,163	(16,682)
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	1,119		1,119
Excess tax benefit (deficiency) from stock-based compensation	(278)		(278)
Vesting of common stock and restricted stock under equity award plans	(1,412)	3	(1,309)			(106)
Vesting of common stock and restricted stock under equity award plans, shares		263
Repurchase of common stock	(6,200)					(6,200)
Retirement of treasury stock		(5)	(3,995)	(3,343)		7,343
Retirement of treasury stock, shares		(500)
Comprehensive income (loss)	8,529			(757)	9,286
Ending Balance at Mar. 31, 2012	$ 575,324	$ 441	$ 276,694	$ 287,703	$ 13,722	$ (3,236)
Ending Balance, shares at Mar. 31, 2012		44,069