Accumulated Other Comprehensive Earnings (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Accumulated other comprehensive earnings (loss), net of tax
Balance at the beginning of the period			$ 763,327
Balance at the end of the period	$ 752,819	$ 752,608	752,819	$ 752,608
Foreign Currency Translation
Accumulated other comprehensive earnings (loss), net of tax
Balance at the beginning of the period	(24,978)	(27,042)	(24,581)	(23,368)
Other comprehensive earnings (loss) before reclassifications	590	610	193	(3,064)
Other comprehensive earnings (loss) net of tax	590	610	193	(3,064)
Balance at the end of the period	(24,388)	(26,432)	(24,388)	(26,432)
Investments
Accumulated other comprehensive earnings (loss), net of tax
Balance at the beginning of the period	1,116	55	1,992	882
Other comprehensive earnings (loss) before reclassifications	(283)	2,592	(1,159)	1,765
Reclassifications from accumulated other comprehensive loss	(40)		(40)
Other comprehensive earnings (loss) net of tax	(323)	2,592	(1,199)	1,765
Balance at the end of the period	793	2,647	793	2,647
Foreign Currency Derivatives
Accumulated other comprehensive earnings (loss), net of tax
Balance at the beginning of the period	572	(71)	589	10
Other comprehensive earnings (loss) before reclassifications	70	267	131	112
Reclassifications from accumulated other comprehensive loss	(99)	128	(177)	202
Other comprehensive earnings (loss) net of tax	(29)	395	(46)	314
Balance at the end of the period	543	324	543	324
Commodity Derivatives
Accumulated other comprehensive earnings (loss), net of tax
Balance at the beginning of the period	508	(364)	713	92
Other comprehensive earnings (loss) before reclassifications	568	294	869	(280)
Reclassifications from accumulated other comprehensive loss	(504)		(1,010)	118
Other comprehensive earnings (loss) net of tax	64	294	(141)	(162)
Balance at the end of the period	572	(70)	572	(70)
Postretirement and Pension Benefits
Accumulated other comprehensive earnings (loss), net of tax
Balance at the beginning of the period	1,205	1,883	1,472	2,139
Reclassifications from accumulated other comprehensive loss	(266)	(256)	(533)	(512)
Other comprehensive earnings (loss) net of tax	(266)	(256)	(533)	(512)
Balance at the end of the period	939	1,627	939	1,627
Accumulated Other Comprehensive Earnings (Loss).
Accumulated other comprehensive earnings (loss), net of tax
Balance at the beginning of the period	(21,577)	(25,539)	(19,815)	(20,245)
Other comprehensive earnings (loss) before reclassifications	945	3,763	34	(1,467)
Reclassifications from accumulated other comprehensive loss	(909)	(128)	(1,760)	(192)
Other comprehensive earnings (loss) net of tax	36	3,635	(1,726)	(1,659)
Balance at the end of the period	$ (21,541)	$ (21,904)	$ (21,541)	$ (21,904)