Consolidated Statements of Shareholders' Equity - USD ($) $ in Thousands	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Treasury Stock [Member]	Total
Balance (in shares) at Dec. 31, 2012	92,374,539			5,424,847
Balance at Dec. 31, 2012	$ 923	$ 271,962	$ 210,003	$ (20,014)	$ 462,874
Net income			39,997		39,997
Stock-based compensation expense		11,997			11,997
Total Number of Shares Purchased (in shares)				1,101,458
Purchase of treasury stock				$ (25,000)	$ (25,000)
Exercise of stock options (in shares)	1,305,538				1,305,538
Exercise of stock options	$ 12	9,248			$ 9,260
Vesting of restricted stock awards and units, net of shares withheld for employee tax (in shares)	146,376
Vesting of restricted stock awards and units, net of shares withheld for employee tax	$ 1	(1,923)			(1,922)
Excess tax benefit from exercise of stock options		5,233			5,233
Balance (in shares) at Dec. 31, 2013	93,826,453			6,526,305
Balance at Dec. 31, 2013	$ 936	296,517	250,000	$ (45,014)	502,439
Net income			13,947		13,947
Stock-based compensation expense		13,356			$ 13,356
Exercise of stock options (in shares)	516,552				516,552
Exercise of stock options	$ 5	4,105			$ 4,110
Vesting of restricted stock awards and units, net of shares withheld for employee tax (in shares)	168,439
Vesting of restricted stock awards and units, net of shares withheld for employee tax	$ 2	(1,660)			(1,658)
Excess tax benefit from exercise of stock options		1,795			1,795
Balance (in shares) at Dec. 31, 2014	94,511,444			6,526,305
Balance at Dec. 31, 2014	$ 943	313,214	263,947	$ (45,014)	533,090
Shortfall due to exercise of stock options		(323)			(323)
Deferred tax asset reversal for unexercised stock options		(576)			(576)
Net income			24,527		24,527
Stock-based compensation expense		14,297			14,297
Total Number of Shares Purchased (in shares)				4,747,441
Purchase of treasury stock				$ (50,000)	$ (50,000)
Exercise of stock options (in shares)	577,559				577,559
Exercise of stock options	$ 7	4,180			$ 4,187
Vesting of restricted stock awards and units, net of shares withheld for employee tax (in shares)	174,458
Vesting of restricted stock awards and units, net of shares withheld for employee tax	$ 2	(1,031)			(1,029)
Excess tax benefit from exercise of stock options		1,569			1,569
Balance (in shares) at Dec. 31, 2015	95,263,461			11,273,746
Balance at Dec. 31, 2015	$ 952	330,290	$ 288,474	$ (95,014)	524,702
Shortfall due to exercise of stock options		(827)			(827)
Deferred tax asset reversal for unexercised stock options		$ (1,112)			$ (1,112)