Consolidated Condensed Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Statement Of Income And Comprehensive Income [Abstract]
Net income	$ 11,893	$ 19,820
Other comprehensive loss, gross of tax:
Foreign currency translation adjustments gain (loss)	7,910	(19,605)
Unrealized gain (loss) on foreign currency derivative securities	1,293	(347)
Unrealized gain on commodity derivative securities	296	76
Other comprehensive income (loss), gross of tax	9,499	(19,876)
Other comprehensive income (loss), related tax effect:
Foreign currency translation adjustments gain (loss)	1,242	467
Unrealized gain (loss) on foreign currency derivative securities	(347)
Unrealized gain on commodity derivative securities	(109)	89
Other comprehensive income (loss), related tax effect	786	556
Other comprehensive income (loss), net of tax	10,285	(19,320)
Comprehensive income	$ 22,178	$ 500