Employee Benefit Plans - Actual and Target Allocations of Plan Assets (Details)	Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Plan, Plan Assets, Allocations [Abstract]
Actual plan asset allocations	100.00%	100.00%
Target plan asset allocations	100.00%
Common stocks [Member]
Defined Benefit Plan, Plan Assets, Allocations [Abstract]
Actual plan asset allocations	36.00%	57.00%
Target plan asset allocations	40.00%
Fixed income investments [Member]
Defined Benefit Plan, Plan Assets, Allocations [Abstract]
Actual plan asset allocations	55.00%	33.00%
Target plan asset allocations	55.00%
Real estate funds [Member]
Defined Benefit Plan, Plan Assets, Allocations [Abstract]
Actual plan asset allocations	9.00%	10.00%
Target plan asset allocations	5.00%