Supplemental Financial Information - Accrued Liabilities (Details) - USD ($) $ in Millions		Jun. 30, 2020	Dec. 31, 2019
Accrued Liabilities, Current [Abstract]
Deferred Payroll Support Program grant proceeds		$ 957	$ 0
Voluntary Separation 2020		307	0
Profitsharing and savings plans		26	695
Vacation pay		454	434
Health		104	120
Workers compensation		159	166
Property and income taxes		72	79
Other		233	250
Accrued liabilities		2,372	1,749
Interest rate derivatives | Accrued Liabilities [Member]
Accrued Liabilities, Current [Abstract]
Derivative contracts	[1]	$ 60	$ 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.