Casualty, Environmental and Other Reserves - Schedule of Claims Activity (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Loss Contingency Accrual [Roll Forward]
Balance at beginning of period	$ 324	$ 374	$ 374
Charged to Expense	107	72	114
Payments	(126)	(122)	(114)
Balance end of period	305	324	374
Casualty Reserves
Loss Contingency Accrual [Roll Forward]
Balance at beginning of period	199	228	229
Charged to Expense	56	21	43
Payments	(68)	(50)	(44)
Balance end of period	187	199	228
Environmental Reserves
Loss Contingency Accrual [Roll Forward]
Balance at beginning of period	80	90	95
Charged to Expense	17	10	26
Payments	(23)	(20)	(31)
Balance end of period	74	80	90
Other Reserves
Loss Contingency Accrual [Roll Forward]
Balance at beginning of period	45	56	50
Charged to Expense	34	41	45
Payments	(35)	(52)	(39)
Balance end of period	$ 44	$ 45	$ 56