Casualty, Environmental and Other Reserves - Schedule of Casualty, Environmental and Other Reserves (Details) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
Loss Contingencies [Line Items]
Current	$ 112	$ 113
Long-term	207	211
Total	319	324
Total Casualty
Loss Contingencies [Line Items]
Current	51	50
Long-term	144	149
Total	195	199
Personal Injury
Loss Contingencies [Line Items]
Current	41	40
Long-term	100	103
Total	141	143
Occupational
Loss Contingencies [Line Items]
Current	10	10
Long-term	44	46
Total	54	56
Environmental
Loss Contingencies [Line Items]
Current	38	39
Long-term	42	41
Total	80	80
Other
Loss Contingencies [Line Items]
Current	23	24
Long-term	21	21
Total	$ 44	$ 45