Accumulated Other Comprehensive Income (Loss) (Reclassifications out of AOCI) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net of tax	$ (2,772)	$ (2,551)	$ (5,514)	$ (4,951)
Amortization of actuarial losses
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassification	(3,089)	(2,857)	(6,148)	(5,514)
Prior service costs
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassification	(155)	(138)	(308)	(279)
Pension and other post-retirement effects
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Tax benefit	472	444	942	842
Net of tax	$ (2,772)	$ (2,551)	$ (5,514)	$ (4,951)