Consolidated Condensed Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Statement Of Income And Comprehensive Income [Abstract]
Net income	$ 27,665	$ 17,288	$ 66,979	$ 50,290
Other comprehensive loss, gross of tax:
Foreign currency translation adjustments loss	(4,429)	(13,178)	(19,312)	(16,533)
Unrealized loss on foreign currency derivative securities	(460)	(529)	(1,237)	(330)
Unrealized loss on commodity derivative securities	(373)		(421)
Other comprehensive loss, gross of tax	(5,262)	(13,707)	(20,970)	(16,863)
Other comprehensive loss, related tax effect:
Foreign currency translation adjustments loss	51	8	764	862
Unrealized loss on foreign currency derivative securities	125		335
Unrealized loss on commodity derivative securities	155		155
Other comprehensive loss, related tax effect	331	8	1,254	862
Other comprehensive loss, net of tax	(4,931)	(13,699)	(19,716)	(16,001)
Comprehensive income	$ 22,734	$ 3,589	$ 47,263	$ 34,289