Employee Benefits Allocation of Plan Assets (Details)	Dec. 31, 2019	Dec. 31, 2018
Allocation of Plan Assets
Defined benefit plan, plan assets, target allocation, percentage	100.00%
Defined benefit plan, actual plan asset allocations	100.00%	100.00%
Alternative Investments
Allocation of Plan Assets
Defined benefit plan, plan assets, target allocation, percentage	25.00%
Defined benefit plan, actual plan asset allocations	25.00%	26.00%
Equity securities
Allocation of Plan Assets
Defined benefit plan, plan assets, target allocation, percentage	25.00%
Defined benefit plan, actual plan asset allocations	25.00%	22.00%
Fixed income securities
Allocation of Plan Assets
Defined benefit plan, plan assets, target allocation, percentage	20.00%
Defined benefit plan, actual plan asset allocations	19.00%	21.00%
Liability driven investments
Allocation of Plan Assets
Defined benefit plan, plan assets, target allocation, percentage	14.00%
Defined benefit plan, actual plan asset allocations	14.00%	16.00%
Real estate
Allocation of Plan Assets
Defined benefit plan, plan assets, target allocation, percentage	9.00%
Defined benefit plan, actual plan asset allocations	9.00%	6.00%
Other plan assets
Allocation of Plan Assets
Defined benefit plan, plan assets, target allocation, percentage	7.00%
Defined benefit plan, actual plan asset allocations	8.00%	9.00%