Accumulated Other Comprehensive Earnings (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Accumulated other comprehensive earnings (loss), net of tax
Balance at the beginning of the period	$ 711,364
Balance at the end of the period	706,665	$ 697,164
AOCI from Derivatives | Foreign currency forward contracts
Accumulated other comprehensive earnings (loss), net of tax
Balance at the beginning of the period	(76)	(1,675)
Other comprehensive earnings (loss) before reclassifications	15	427
Reclassifications from accumulated other comprehensive loss	16	387
Other comprehensive earnings (loss) net of tax	31	814
Balance at the end of the period	(45)	(861)
AOCI from Derivatives | Commodity futures contracts
Accumulated other comprehensive earnings (loss), net of tax
Balance at the beginning of the period	1,114	173
Other comprehensive earnings (loss) before reclassifications	(366)	187
Reclassifications from accumulated other comprehensive loss	(732)	4
Other comprehensive earnings (loss) net of tax	(1,098)	191
Balance at the end of the period	16	364
Investments
Accumulated other comprehensive earnings (loss), net of tax
Balance at the beginning of the period	(697)	(605)
Other comprehensive earnings (loss) before reclassifications	148	312
Reclassifications from accumulated other comprehensive loss		3
Other comprehensive earnings (loss) net of tax	148	315
Balance at the end of the period	(549)	(290)
Postretirement and Pension Benefits
Accumulated other comprehensive earnings (loss), net of tax
Balance at the beginning of the period	4,873	6,387
Other comprehensive earnings (loss) before reclassifications	4
Reclassifications from accumulated other comprehensive loss	(233)	(262)
Other comprehensive earnings (loss) net of tax	(229)	(262)
Balance at the end of the period	4,644	6,125
Foreign Currency Translation
Accumulated other comprehensive earnings (loss), net of tax
Balance at the beginning of the period	(25,460)	(21,644)
Other comprehensive earnings (loss) before reclassifications	2,100	205
Other comprehensive earnings (loss) net of tax	2,100	205
Balance at the end of the period	(23,360)	(21,439)
Accumulated Other Comprehensive Earnings ( Loss )
Accumulated other comprehensive earnings (loss), net of tax
Balance at the beginning of the period	(20,246)	(17,364)
Other comprehensive earnings (loss) before reclassifications	1,901	1,131
Reclassifications from accumulated other comprehensive loss	(949)	132
Other comprehensive earnings (loss) net of tax	952	1,263
Balance at the end of the period	$ (19,294)	$ (16,101)