Employee Benefit Plans - Weighted-average Asset Allocation by Asset Category (Details)	Dec. 31, 2019	Dec. 31, 2018
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Actual asset allocations	100.00%	100.00%
Fixed Income
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Actual asset allocations	61.80%	68.00%
Equity
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Actual asset allocations	27.50%	25.20%
Cash and Accrued Income
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Actual asset allocations	10.70%	6.80%