CONSOLIDATED STATEMENTS OF CHANGES IN SHAREHOLDERS' EQUITY (USD $) In Thousands, except Share data, unless otherwise specified	Total	Common Stock	Additional Paid in Capital	Accumulated Other Comprehensive Loss	Retained Earnings	Treasury Stock
Balance at Dec. 31, 2009	$ 315,893	$ 330	$ 233,111	$ (3,056)	$ 86,164	$ (656)
Balance (in shares) at Dec. 31, 2009		32,992,000
Increase (Decrease) in Shareholders' Equity
Net income	20,896				20,896
Other comprehensive income (loss)	2,777			2,777
Issuance of Common Stock in connection with the exercise of stock options	5,027	4	5,023
Issuance of Common Stock in connection with the exercise of stock options (in shares)		374,000
Proceeds from sale of stock	7,356	5	7,351
Proceeds from sale of stock (in shares)		488,000
Forfeiture of restricted stock units (in shares)		(33,000)
Issuance of restricted stock units		5	(5)
Issuance of restricted stock units (in shares)		531,000
Stock-based compensation expense	9,597		9,597
Tax benefit associated with vesting of restricted stock units	2,342		2,342
Balance at Dec. 31, 2010	363,888	344	257,419	(279)	107,060	(656)
Balance (in shares) at Dec. 31, 2010		34,352,000
Increase (Decrease) in Shareholders' Equity
Net income	54,477				54,477
Other comprehensive income (loss)	(906)			(906)
Issuance of Common Stock in connection with the exercise of stock options	2,680	4	2,676
Issuance of Common Stock in connection with the exercise of stock options (in shares)		417,000
Forfeiture of restricted stock units		(1)	1
Forfeiture of restricted stock units (in shares)		(63,000)
Issuance of restricted stock units		5	(5)
Issuance of restricted stock units (in shares)		548,000
Purchase and retirement of common stock	(2,107)	(1)	(2,106)
Purchase and retirement of common stock (in shares)		(127,000)
Stock-based compensation expense	8,088		8,088
Tax benefit associated with vesting of restricted stock units	2,462		2,462
Balance at Dec. 31, 2011	428,582	351	268,535	(1,185)	161,537	(656)
Balance (in shares) at Dec. 31, 2011		35,127,000
Increase (Decrease) in Shareholders' Equity
Net income	63,692				63,692
Other comprehensive income (loss)	(734)			(734)
Issuance of Common Stock in connection with the exercise of stock options	3,560	3	3,557
Issuance of Common Stock in connection with the exercise of stock options (in shares)		239,000
Forfeiture of restricted stock units		(2)	2
Forfeiture of restricted stock units (in shares)		(231,000)
Issuance of restricted stock units		5	(5)
Issuance of restricted stock units (in shares)		532,000
Purchase and retirement of common stock	(1,350)	(1)	(1,349)
Purchase and retirement of common stock (in shares)		(49,000)
Stock-based compensation expense	8,061		8,061
Tax benefit associated with vesting of restricted stock units	1,283		1,283
Balance at Dec. 31, 2012	$ 503,094	$ 356	$ 280,084	$ (1,919)	$ 225,229	$ (656)
Balance (in shares) at Dec. 31, 2012		35,618,000