Accumulated Other Comprehensive Earnings (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Accumulated other comprehensive earnings (loss), net of tax
Balance at the beginning of the period			$ 759,854
Balance at the end of the period	$ 752,608	$ 742,804	752,608	$ 742,804
Foreign Currency Translation
Accumulated other comprehensive earnings (loss), net of tax
Balance at the beginning of the period	(27,042)	(23,768)	(23,368)	(24,159)
Other comprehensive earnings (loss) before reclassifications	610	205	(3,064)	596
Other comprehensive earnings (loss) net of tax	610	205	(3,064)	596
Balance at the end of the period	(26,432)	(23,563)	(26,432)	(23,563)
Investments
Accumulated other comprehensive earnings (loss), net of tax
Balance at the beginning of the period	55	(404)	882	(1,516)
Other comprehensive earnings (loss) before reclassifications	2,592	898	1,765	2,010
Other comprehensive earnings (loss) net of tax	2,592	898	1,765	2,010
Balance at the end of the period	2,647	494	2,647	494
Foreign Currency Derivatives
Accumulated other comprehensive earnings (loss), net of tax
Balance at the beginning of the period	(71)	(150)	10	(309)
Other comprehensive earnings (loss) before reclassifications	267	137	112	296
Reclassifications from accumulated other comprehensive loss	128		202
Other comprehensive earnings (loss) net of tax	395	137	314	296
Balance at the end of the period	324	(13)	324	(13)
Commodity Derivatives
Accumulated other comprehensive earnings (loss), net of tax
Balance at the beginning of the period	(364)	(114)	92	(444)
Other comprehensive earnings (loss) before reclassifications	294	(94)	(280)	164
Reclassifications from accumulated other comprehensive loss		124	118	196
Other comprehensive earnings (loss) net of tax	294	30	(162)	360
Balance at the end of the period	(70)	(84)	(70)	(84)
Postretirement and Pension Benefits
Accumulated other comprehensive earnings (loss), net of tax
Balance at the beginning of the period	1,883	3,918	2,139	4,206
Reclassifications from accumulated other comprehensive loss	(256)	(289)	(512)	(577)
Other comprehensive earnings (loss) net of tax	(256)	(289)	(512)	(577)
Balance at the end of the period	1,627	3,629	1,627	3,629
Accumulated Other Comprehensive Earnings ( Loss )
Accumulated other comprehensive earnings (loss), net of tax
Balance at the beginning of the period	(25,539)	(20,518)	(20,245)	(22,222)
Other comprehensive earnings (loss) before reclassifications	3,763	1,146	(1,467)	3,066
Reclassifications from accumulated other comprehensive loss	(128)	(165)	(192)	(381)
Other comprehensive earnings (loss) net of tax	3,635	981	(1,659)	2,685
Balance at the end of the period	$ (21,904)	$ (19,537)	$ (21,904)	$ (19,537)