CONSOLIDATED CONDENSED STATEMENT OF SHAREHOLDERS' EQUITY - 6 months ended Jun. 30, 2016 - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Retained Earnings	Accumulated Other Comprehensive Loss	Treasury Stock
Beginning Balance (in shares) at Dec. 31, 2015		(93,769)				(2)
Beginning Balance at Dec. 31, 2015	$ 412,945	$ 938	$ 322,793	$ 101,047	$ (11,813)	$ (20)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Acquisition of treasury stock (in shares)						(571)
Acquisition of treasury stock	(5,133)					$ (5,133)
Exercise of stock options (in shares)		0				299
Exercise of stock options	2,096	$ 0	(541)			$ 2,637
Compensatory awards released from restriction (in shares)		440				91
Compensatory awards released from restriction		$ 4	(821)			$ 817
Share-based compensation	4,329		4,329
Stock dividends (in shares)		5				0
Stock dividends			45	(53)		$ 8
Cash dividends	(1,882)			(1,882)
Equity adjustment from foreign currency translation	3,618				3,618
Change in fair value of derivative instruments	(2,223)
Change in fair value of derivative instruments	(2,161)				(2,161)
Net income	72,495			72,495
Ending Balance (in shares) at Jun. 30, 2016		(94,214)				(183)
Ending Balance at Jun. 30, 2016	$ 486,307	$ 942	$ 325,805	$ 171,607	$ (10,356)	$ (1,691)