Supplemental Financial Information - Accrued Liabilities (Details) - USD ($) $ in Millions		Mar. 31, 2020	Dec. 31, 2019
Accrued Liabilities, Current [Abstract]
Profitsharing and savings plans		$ 25	$ 695
Vacation pay		443	434
Health		99	120
Workers compensation		168	166
Property and income taxes		67	79
Other		180	250
Accrued liabilities		1,037	1,749
Interest rate derivatives | Accrued Liabilities [Member]
Accrued Liabilities, Current [Abstract]
Derivative contracts	[1]	$ 55	$ 5

[1] The net amounts of derivative assets and liabilities are reconciled to the individual line item amounts presented in the unaudited Condensed Consolidated Balance Sheet in Note 10.