CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (USD $) In Thousands, unless otherwise specified	Total	Common Stock	Retained Earnings	Accumulated Other Comprehensive Income (Loss)
Beginning balance at Dec. 31, 2011	$ 357,089	$ 166,231	$ 190,708	$ 150
Beginning balance, shares at Dec. 31, 2011		42,008
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	19,710		19,710
Other comprehensive income	(1,332)			(1,332)
Excess tax benefits from stock-based compensation	877	877
Stock-based compensation expense	1,917	1,917
Options exercised	5,156	5,156
Options exercised, shares		610
Issuance of common stock under Employee Stock Purchase Plans	430	430
Issuance of common stock under Employee Stock Purchase Plans, shares		33
Shares surrendered in exchange for payment of payroll tax liabilities	(439)	(439)
Shares surrendered in exchange for payment of payroll tax liabilities, shares		(31)
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)
Ending balance at Dec. 31, 2012	381,577	172,341	210,418	(1,182)
Ending balance, shares at Dec. 31, 2012		42,489
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	16,570		16,570
Other comprehensive income	2,125			2,125
Excess tax benefits from stock-based compensation	259	259
Stock-based compensation expense	1,467	1,467
Options exercised	3,733	3,733
Options exercised, shares		413
Issuance of common stock under Employee Stock Purchase Plans	448	448
Issuance of common stock under Employee Stock Purchase Plans, shares		37
Shares surrendered in exchange for payment of payroll tax liabilities	(21)	(21)
Shares surrendered in exchange for payment of payroll tax liabilities, shares		(48)
Shares surrendered in exchange for the exercise of stock options	(452)	(452)
Shares surrendered in exchange for the exercise of stock options, shares		(45)
Ending balance at Dec. 31, 2013	405,706	177,775	226,988	943
Ending balance, shares at Dec. 31, 2013		42,846
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	22,974		22,974
Other comprehensive income	(3,355)			(3,355)
Excess tax benefits from stock-based compensation	576	576
Stock-based compensation expense	1,460	1,460
Options exercised	9,638	9,638
Options exercised, shares	878	878
Issuance of common stock under Employee Stock Purchase Plans	450	450
Issuance of common stock under Employee Stock Purchase Plans, shares		33
Shares surrendered in exchange for payment of payroll tax liabilities	(249)	(249)
Shares surrendered in exchange for payment of payroll tax liabilities, shares		(16)
Shares surrendered in exchange for the exercise of stock options	(1,941)	(1,941)
Shares surrendered in exchange for the exercise of stock options, shares		(127)
Ending balance at Dec. 31, 2014	$ 435,259	$ 187,709	$ 249,962	$ (2,412)
Ending balance, shares at Dec. 31, 2014		43,614