Schedule I - Condensed Financial Information of the Parent (Condensed Statements of Comprehensive Income) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Condensed Financial Statements, Captions [Line Items]
Other, net	$ (1,140)	$ (527)
Other (income) expense	(810)	(4,579)
Administrative and general expenses	53,062	53,783
Income tax provision (benefit)	(535)	3,767
Net income	14,793	39,632
Current period pension and postretirement plan adjustment, net of $213 tax benefit and $226 tax expense in 2020 and 2019, respectively	(697)	758
Pension settlement, net of $202 tax benefit in 2019	0	671
Reclassification of pension and postretirement adjustments into earnings, net of $129 and $90 tax benefit in 2020 and 2019, respectively	435	845
Total other comprehensive income	(262)	2,274
Comprehensive income	14,531	41,906
Current period pension and postretirement plan adjustment, tax (benefit) expense	(213)	226
Pension settlement, tax		202
Reclassification of pension and post retirement adjustments into earnings, tax benefit	129	90
Parent Company
Condensed Financial Statements, Captions [Line Items]
Intercompany interest expense	1,178	1,190
Other, net	(1,003)	(1,796)
Other (income) expense	175	(606)
Administrative and general expenses	5,658	6,403
Loss before income taxes	(5,833)	(5,797)
Income tax provision (benefit)	2,419	(3,819)
Net loss before equity in earnings of subsidiaries	(8,252)	(1,978)
Equity in earnings of subsidiaries	(23,045)	(41,610)
Net income	14,793	39,632
Current period pension and postretirement plan adjustment, net of $213 tax benefit and $226 tax expense in 2020 and 2019, respectively	(697)	758
Pension settlement, net of $202 tax benefit in 2019	0	671
Reclassification of pension and postretirement adjustments into earnings, net of $129 and $90 tax benefit in 2020 and 2019, respectively	435	845
Total other comprehensive income	(262)	2,274
Comprehensive income	14,531	41,906
Current period pension and postretirement plan adjustment, tax (benefit) expense	(213)	226
Pension settlement, tax		202
Reclassification of pension and post retirement adjustments into earnings, tax benefit	$ 129	$ 90