CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (USD $) In Thousands, except Share data, unless otherwise specified	Total	Common Stock	Retained Earnings	Accumulated Other Comprehensive Income (Loss)
Beginning balance at Dec. 31, 2010	$ 235,615	$ 67,091	$ 167,664	$ 860
Beginning balance, shares at Dec. 31, 2010		35,496,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	23,044		23,044
Other comprehensive loss, net of tax	(710)			(710)
Excess tax benefits from stock-based compensation	3,122	3,122
Stock-based compensation expense	1,644	1,644
Issuance of common stock, net of offering costs	87,700	87,700
Issuance of common stock, net of offering costs, shares		5,520,000
Issuance of common stock under Employee Stock Purchase Plans	430	430
Issuance of common stock under Employee Stock Purchase Plans, shares		31,000
Options exercised	8,449	8,449
Options exercised, shares		1,099,000
Shares surrendered in exchange for payment of payroll tax liabilities	953	953
Shares surrendered in exchange for payment of payroll tax liabilities, shares		(60,000)
Shares surrendered in exchange for the exercise of stock options	(1,252)	(1,252)
Shares surrendered in exchange for the exercise of stock options, shares	(78,000)	(78,000)
Ending balance at Dec. 31, 2011	357,089	166,231	190,708	150
Ending balance, shares at Dec. 31, 2011		42,008,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	19,710		19,710
Other comprehensive loss, net of tax	(1,332)			(1,332)
Excess tax benefits from stock-based compensation	877	877
Stock-based compensation expense	1,917	1,917
Issuance of common stock under Employee Stock Purchase Plans	430	430
Issuance of common stock under Employee Stock Purchase Plans, shares		33,000
Options exercised	5,156	5,156
Options exercised, shares		610,000
Shares surrendered in exchange for payment of payroll tax liabilities	(439)	(439)
Shares surrendered in exchange for payment of payroll tax liabilities, shares		(31,000)
Shares surrendered in exchange for the exercise of stock options	(1,831)	(1,831)
Shares surrendered in exchange for the exercise of stock options, shares	(131,000)	(131,000)
Ending balance at Dec. 31, 2012	381,577	172,341	210,418	(1,182)
Ending balance, shares at Dec. 31, 2012		42,489,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	16,570		16,570
Other comprehensive loss, net of tax	2,125			2,125
Excess tax benefits from stock-based compensation	259	259
Stock-based compensation expense	1,467	1,467
Issuance of common stock under Employee Stock Purchase Plans	448	448
Issuance of common stock under Employee Stock Purchase Plans, shares		37,000
Options exercised	3,733	3,733
Options exercised, shares	368,000	413,000
Shares surrendered in exchange for payment of payroll tax liabilities	(21)	(21)
Shares surrendered in exchange for payment of payroll tax liabilities, shares		(48,000)
Shares surrendered in exchange for the exercise of stock options	(452)	(452)
Shares surrendered in exchange for the exercise of stock options, shares	(45,000)	(45,000)
Ending balance at Dec. 31, 2013	$ 405,706	$ 177,775	$ 226,988	$ 943
Ending balance, shares at Dec. 31, 2013		42,846,000