Benefit Plans, Weighted Average Asset Allocation by Asset Category (Details)	Dec. 31, 2018	Dec. 31, 2017
Weighted average asset allocations [Abstract]
Weighted average asset allocation percentages, Total	100.00%	100.00%
Equity Securities [Member]
Weighted average asset allocations [Abstract]
Weighted average asset allocation percentages, Total	54.90%	56.00%
Fixed Income Securities [Member]
Weighted average asset allocations [Abstract]
Weighted average asset allocation percentages, Total	38.30%	36.20%
Real Estate [Member]
Weighted average asset allocations [Abstract]
Weighted average asset allocation percentages, Total	0.80%	0.80%
Other [Member]
Weighted average asset allocations [Abstract]
Weighted average asset allocation percentages, Total	6.00%	7.00%