CONDENSED CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY - 6 months ended Jun. 30, 2015 - USD ($) $ in Thousands	Total	Capital Stock [Member]	Additional Paid-In Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]
Beginning Balance at Dec. 31, 2014	$ 581,963	$ 18,404	$ 137,225	$ 491,428	$ (65,094)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	27,167			27,167
Other comprehensive income (loss)	(18,785)				(18,785)
Stock options exercised	6,515	164	6,351
Stock issued to directors	0	15	(15)
Shares issued for employees stock purchase plan	345	6	339
Shares issued for restricted stock	(2,342)	60	(2,402)
Stock-based compensation expense	5,026		5,026
Ending Balance at Jun. 30, 2015	$ 599,889	$ 18,649	$ 146,524	$ 518,595	$ (83,879)