Pension and Other Post-Retirement Benefit Plans (Unrecognized Net Periodic Benefit Expense) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlement	$ (424)	$ 0	$ 0
Unrecognized prior service cost	0	0
Unrecognized net actuarial loss	111,820	89,871
Accumulated other comprehensive loss	111,820	89,871
Post-Retirement Healthcare Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlement	(17)	0	$ 0
Unrecognized prior service cost	0	0
Unrecognized net actuarial loss	833	1,031
Accumulated other comprehensive loss	$ 833	$ 1,031