Consolidated Condensed Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Statement Of Income And Comprehensive Income [Abstract]
Net income	$ 6,554	$ 20,223	$ 40,469	$ 50,562
Other comprehensive income (loss), gross of tax:
Foreign currency translation adjustments gain	13,251	2,230	42,051	2,866
Unrealized (loss) gain on foreign currency derivative securities	(1,234)	(868)	2,541	(624)
Unrealized gain on commodity derivative securities	136	139	184	544
Other comprehensive income, gross of tax	12,153	1,501	44,776	2,786
Other comprehensive income (loss), related tax effect:
Foreign currency translation adjustments gain	(49)	(13)	(158)	1,087
Unrealized (loss) gain on foreign currency derivative securities	331	233	(683)	168
Unrealized gain on commodity derivative securities	(50)	(51)	(67)	(201)
Other comprehensive income (loss), related tax effect	232	169	(908)	1,054
Other comprehensive income, net of tax	12,385	1,670	43,868	3,840
Comprehensive income	$ 18,939	$ 21,893	$ 84,337	$ 54,402