Accumulated Other Comprehensive Earnings (Loss) (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015
Accumulated other comprehensive earnings (loss), net of tax
Balance at the beginning of the period	$ 698,183
Balance at the end of the period	700,135	$ 685,855
AOCI from Derivatives | Foreign currency forward contracts
Accumulated other comprehensive earnings (loss), net of tax
Balance at the beginning of the period	(1,675)	(1,236)
Other comprehensive earnings (loss) before reclassifications	440	(1,006)
Reclassifications from accumulated other comprehensive loss	655	651
Other comprehensive earnings (loss) net of tax	1,095	(355)
Balance at the end of the period	(580)	(1,591)
AOCI from Derivatives | Commodity futures contracts
Accumulated other comprehensive earnings (loss), net of tax
Balance at the beginning of the period	173	(470)
Other comprehensive earnings (loss) before reclassifications	1,552	(599)
Reclassifications from accumulated other comprehensive loss	(27)	417
Other comprehensive earnings (loss) net of tax	1,525	(182)
Balance at the end of the period	1,698	(652)
Investments
Accumulated other comprehensive earnings (loss), net of tax
Balance at the beginning of the period	(605)	(332)
Other comprehensive earnings (loss) before reclassifications	637	1
Reclassifications from accumulated other comprehensive loss	3
Other comprehensive earnings (loss) net of tax	640	1
Balance at the end of the period	35	(331)
Postretirement and Pension Benefits
Accumulated other comprehensive earnings (loss), net of tax
Balance at the beginning of the period	6,387	6,439
Reclassifications from accumulated other comprehensive loss	(524)	(464)
Other comprehensive earnings (loss) net of tax	(524)	(464)
Balance at the end of the period	5,863	5,975
Foreign Currency Translation
Accumulated other comprehensive earnings (loss), net of tax
Balance at the beginning of the period	(21,644)	(17,499)
Other comprehensive earnings (loss) before reclassifications	(1,431)	(1,711)
Other comprehensive earnings (loss) net of tax	(1,431)	(1,711)
Balance at the end of the period	(23,075)	(19,210)
Accumulated Other Comprehensive Earnings ( Loss )
Accumulated other comprehensive earnings (loss), net of tax
Balance at the beginning of the period	(17,364)	(13,098)
Other comprehensive earnings (loss) before reclassifications	1,198	(3,315)
Reclassifications from accumulated other comprehensive loss	107	604
Other comprehensive earnings (loss) net of tax	1,305	(2,711)
Balance at the end of the period	$ (16,059)	$ (15,809)