Benefit Plans (Asset Allocations) (Details)	Dec. 31, 2020
Equity Securities [Member] | Pension [Member]
Defined Benefit Plan Disclosure [Line Items]
Composition of plan assets	31.00%
Equity Securities [Member] | Postretirement Benefit Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Composition of plan assets	58.00%
Corporate Bonds [Member] | Pension [Member]
Defined Benefit Plan Disclosure [Line Items]
Composition of plan assets	53.00%
Corporate Bonds [Member] | Postretirement Benefit Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Composition of plan assets	31.00%
US Treasury And Foreign Government Securities [Member] | Pension [Member]
Defined Benefit Plan Disclosure [Line Items]
Composition of plan assets	16.00%
US Treasury And Foreign Government Securities [Member] | Postretirement Benefit Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Composition of plan assets	11.00%