Investment Allocations (Details 6) - Qualified Plan	Dec. 31, 2020
Underfunded Plan | Minimum | Equity securities | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, target allocation, percentage	35.00%
Underfunded Plan | Minimum | Fixed Income Securities | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, target allocation, percentage	55.00%
Underfunded Plan | Maximum | Equity securities | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, target allocation, percentage	45.00%
Underfunded Plan | Maximum | Fixed Income Securities | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, target allocation, percentage	65.00%
Overfunded Plan | Equity securities | Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, target allocation, percentage	10.00%
Overfunded Plan | Fixed Income Securities | Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, target allocation, percentage	90.00%