Accumulated Other Comprehensive Earnings (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 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	$ 756,762	$ 760,965	756,762	$ 760,965
Foreign Currency Translation Adjustment
Accumulated other comprehensive earnings (loss), net of tax
Balance at the beginning of the period	(24,388)	(26,432)	(24,581)	(23,368)
Other comprehensive earnings (loss) before reclassifications	(495)	328	(302)	(2,736)
Other comprehensive earnings (loss) net of tax	(495)	328	(302)	(2,736)
Balance at the end of the period	(24,883)	(26,104)	(24,883)	(26,104)
Investments
Accumulated other comprehensive earnings (loss), net of tax
Balance at the beginning of the period	793	2,647	1,992	882
Other comprehensive earnings (loss) before reclassifications	(496)	(350)	(1,655)	1,415
Reclassifications from accumulated other comprehensive loss	(29)		(69)
Other comprehensive earnings (loss) net of tax	(525)	(350)	(1,724)	1,415
Balance at the end of the period	268	2,297	268	2,297
Foreign Currency Derivatives
Accumulated other comprehensive earnings (loss), net of tax
Balance at the beginning of the period	543	324	589	10
Other comprehensive earnings (loss) before reclassifications	(82)	146	49	258
Reclassifications from accumulated other comprehensive loss	(81)	(62)	(258)	140
Other comprehensive earnings (loss) net of tax	(163)	84	(209)	398
Balance at the end of the period	380	408	380	408
Commodity Derivatives
Accumulated other comprehensive earnings (loss), net of tax
Balance at the beginning of the period	572	(70)	713	92
Other comprehensive earnings (loss) before reclassifications	313	316	1,182	36
Reclassifications from accumulated other comprehensive loss	(618)	69	(1,628)	187
Other comprehensive earnings (loss) net of tax	(305)	385	(446)	223
Balance at the end of the period	267	315	267	315
Postretirement and Pension Benefits
Accumulated other comprehensive earnings (loss), net of tax
Balance at the beginning of the period	939	1,627	1,472	2,139
Reclassifications from accumulated other comprehensive loss	(266)	(255)	(799)	(767)
Other comprehensive earnings (loss) net of tax	(266)	(255)	(799)	(767)
Balance at the end of the period	673	1,372	673	1,372
Accumulated Other Comprehensive Earnings (Loss).
Accumulated other comprehensive earnings (loss), net of tax
Balance at the beginning of the period	(21,541)	(21,904)	(19,815)	(20,245)
Other comprehensive earnings (loss) before reclassifications	(760)	440	(726)	(1,027)
Reclassifications from accumulated other comprehensive loss	(994)	(248)	(2,754)	(440)
Other comprehensive earnings (loss) net of tax	(1,754)	192	(3,480)	(1,467)
Balance at the end of the period	$ (23,295)	$ (21,712)	$ (23,295)	$ (21,712)