Other Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Pension and postretirement benefits [Abstract]
Amortization of net actuarial loss, gross amount	$ 1,309	$ 871	$ 2,992	$ 1,285
Amortization of net actuarial loss, income tax provision	(329)	(219)	(753)	(324)
Amortization of net actuarial loss, net amount	980	652	2,239	961
Actuarial gains (losses), gross amount	2,891	(6,592)	7,019	(10,201)
Actuarial gains (losses), income tax provision	(729)	1,661	(1,764)	2,566
Actuarial gains (losses), net amount	2,162	(4,931)	5,255	(7,635)
Foreign currency translation, gross amount	(122)	(239)	(705)	(1,162)
Foreign currency translation, income tax provision	0	0	0	0
Foreign currency translation, net amount	(122)	(239)	(705)	(1,162)
Total other comprehensive income, gross amount	4,078	(5,960)	9,306	(10,078)
Total other comprehensive income, income tax provision	(1,058)	1,442	(2,517)	2,242
Total other comprehensive income (loss), net of taxes	$ 3,020	$ (4,518)	$ 6,789	$ (7,836)