Pension and Other Postretirement Benefit Costs - Amounts Recognized in Accumulated Other Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Defined Benefit Plan, Amounts Recognized in Other Comprehensive Income (Loss) [Abstract]
Beginning balance	$ (12,681)	$ (10,573)	$ (12,902)	$ (10,733)
Amortization of actuarial losses	301	218	602	436
Total reclassifications before tax	301	218	602	436
Tax benefit	(80)	(58)	(160)	(116)
Total reclassifications for the period	221	160	442	320
Ending balance	$ (12,460)	$ (10,413)	$ (12,460)	$ (10,413)