Consolidated Condensed Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Statement Of Income And Comprehensive Income [Abstract]
Net income	$ 16,659	$ 8,513	$ 29,625	$ 33,915
Other comprehensive income (loss), gross of tax:
Foreign currency translation adjustments (loss) gain	(22,994)	23,285	(11,253)	28,800
Unrealized (loss) gain on foreign currency derivative securities	(1,561)	815	551	3,775
Unrealized gain (loss) on commodity derivative securities		16	(218)	48
Other comprehensive (loss) income, gross of tax	(24,555)	24,116	(10,920)	32,623
Other comprehensive income (loss), related tax effect:
Cumulative effect of accounting change due to ASU 2018-02			(40)
Foreign currency translation adjustments (loss) gain	(156)	(106)	(232)	(109)
Unrealized (loss) gain on foreign currency derivative securities	419	(219)	(148)	(1,014)
Unrealized gain (loss) on commodity derivative securities		(6)	(59)	(17)
Other comprehensive (loss) income, related tax effect	263	(331)	(479)	(1,140)
Other comprehensive (loss) income, net of tax	(24,292)	23,785	(11,399)	31,483
Comprehensive (loss) income	$ (7,633)	$ 32,298	$ 18,226	$ 65,398