Casualty, Environmental and Other Reserves - Schedule of Casualty, Environmental and Other Reserves (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Loss Contingencies [Line Items]
Current	$ 99	$ 100
Long-term	210	205
Total	309	305
Total Casualty
Loss Contingencies [Line Items]
Current	48	48
Long-term	141	139
Total	189	187
Personal Injury
Loss Contingencies [Line Items]
Current	42	42
Long-term	85	87
Total	127	129
Occupational
Loss Contingencies [Line Items]
Current	6	6
Long-term	56	52
Total	62	58
Environmental
Loss Contingencies [Line Items]
Current	31	31
Long-term	46	43
Total	77	74
Other
Loss Contingencies [Line Items]
Current	20	21
Long-term	23	23
Total	$ 43	$ 44