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, 2013	$ 555,527	$ 17,855	$ 110,577	$ 438,545	$ (11,450)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	25,482			25,482
Other comprehensive income (loss)	(1,425)				(1,425)
Stock options exercised	14,062	308	13,754
Stock issued to directors	0	14	(14)
Issuance of stock under stock plans and other	334	9	325
Shares issued for restricted stock	(1,247)	41	(1,288)
Stock-based compensation expense	4,576		4,576
Ending Balance at Jun. 30, 2014	$ 597,309	$ 18,227	$ 127,930	$ 464,027	$ (12,875)