Casualty, Environmental and Other Reserves - Schedule of Casualty, Environmental and Other Reserves (Details) - USD ($) $ in Millions	Jun. 30, 2020	Dec. 31, 2019
Loss Contingencies [Line Items]
Current	$ 103	$ 100
Long-term	203	205
Total	306	305
Total Casualty
Loss Contingencies [Line Items]
Current	53	48
Long-term	135	139
Total	188	187
Personal Injury
Loss Contingencies [Line Items]
Current	44	42
Long-term	83	87
Total	127	129
Occupational
Loss Contingencies [Line Items]
Current	9	6
Long-term	52	52
Total	61	58
Environmental
Loss Contingencies [Line Items]
Current	30	31
Long-term	45	43
Total	75	74
Other
Loss Contingencies [Line Items]
Current	20	21
Long-term	23	23
Total	$ 43	$ 44