Condensed Consolidated Statements of Changes in Shareholders' Equity - 6 months ended Jun. 30, 2016 - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Treasury Stock [Member]
Beginning Balance at Dec. 31, 2015	$ 678,680	$ 428	$ 275,380	$ 458,325	$ (53,662)	$ (1,791)
Beginning Balance, shares at Dec. 31, 2015		42,785
Stock-based compensation expense	5,729		5,729
Excess tax benefit (deficiency) from stock-based compensation	2,060		2,060
Issuance of common stock under equity award plans, net of shares withheld for employee taxes	(4,915)	$ 2	(4,774)			(143)
Issuance of common stock under equity award plans, net of shares withheld for employee taxes, shares		258
Comprehensive income (loss)	27,340			23,092	4,248
Ending Balance at Jun. 30, 2016	$ 708,894	$ 430	$ 278,395	$ 481,417	$ (49,414)	$ (1,934)
Ending Balance, shares at Jun. 30, 2016		43,043