Accumulated Other Comprehensive Earnings (Loss) (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2016	Sep. 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	705,330	$ 693,111
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	391	(1,769)
Reclassifications from accumulated other comprehensive loss	946	1,106
Other comprehensive earnings (loss) net of tax	1,337	(663)
Balance at the end of the period	(338)	(1,899)
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	2,424	(1,125)
Reclassifications from accumulated other comprehensive loss	(533)	1,000
Other comprehensive earnings (loss) net of tax	1,891	(125)
Balance at the end of the period	2,064	(595)
Investments
Accumulated other comprehensive earnings (loss), net of tax
Balance at the beginning of the period	(605)	(332)
Other comprehensive earnings (loss) before reclassifications	451	69
Reclassifications from accumulated other comprehensive loss	3
Other comprehensive earnings (loss) net of tax	454	69
Balance at the end of the period	(151)	(263)
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	(786)	(694)
Other comprehensive earnings (loss) net of tax	(786)	(694)
Balance at the end of the period	5,601	5,745
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	(2,337)	(3,706)
Other comprehensive earnings (loss) net of tax	(2,337)	(3,706)
Balance at the end of the period	(23,981)	(21,205)
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	929	(6,531)
Reclassifications from accumulated other comprehensive loss	(370)	1,412
Other comprehensive earnings (loss) net of tax	559	(5,119)
Balance at the end of the period	$ (16,805)	$ (18,217)