Casualty, Environmental and Other Reserves - Schedule of Casualty, Environmental and Other Reserves (Details) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Loss Contingencies [Line Items]
Current	$ 110	$ 113
Long-term	195	211
Total	305	324
Total Casualty
Loss Contingencies [Line Items]
Current	56	50
Long-term	128	149
Total	184	199
Personal Injury
Loss Contingencies [Line Items]
Current	47	40
Long-term	78	103
Total	125	143
Occupational
Loss Contingencies [Line Items]
Current	9	10
Long-term	50	46
Total	59	56
Environmental
Loss Contingencies [Line Items]
Current	32	39
Long-term	46	41
Total	78	80
Other
Loss Contingencies [Line Items]
Current	22	24
Long-term	21	21
Total	$ 43	$ 45