CONDENSED CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY (USD $) In Thousands, unless otherwise specified	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	13,627			13,627
Other comprehensive income (loss)	(27,494)				(27,494)
Stock options exercised	5,290	137	5,153
Shares issued for employees stock purchase plan	345	6	339
Shares issued for restricted stock	(2,258)	58	(2,316)
Stock-based compensation expense	1,598		1,598
Ending Balance at Mar. 31, 2015	$ 573,071	$ 18,605	$ 141,999	$ 505,055	$ (92,588)