CONDENSED CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY - 9 months ended Sep. 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	39,621			39,621
Other comprehensive income (loss)	(20,595)				(20,595)
Stock options exercised	6,539	164	6,375
Stock issued to directors	0	15	(15)
Shares issued for employees stock purchase plan	727	14	713
Shares issued for restricted stock	(2,405)	63	(2,468)
Shares repurchased	(37,457)	(678)	(36,779)
Stock-based compensation expense	7,734		7,734
Ending Balance at Sep. 30, 2015	$ 576,127	$ 17,982	$ 112,785	$ 531,049	$ (85,689)