Postretirement Benefit Plans (Amounts Recognized in Balance Sheet) (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Defined Benefit Postretirement Health And Life Coverage [Member]
Defined Benefit Plan Disclosure [Line Items]
Accrued benefit liability	$ 342	$ 404
Director's Retirement Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Accrued benefit liability	1,142	1,077
Scottdale Defined Benefit Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Accrued benefit liability	$ 462	$ 183