Lease Commitments - Balance Sheets (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Operating Leases
Right-of-use asset	$ 4,074
Operating lease liability, current	1,277
Noncurrent operating lease liabilities	2,608
Total operating lease liabilities	$ 3,885
Weighted-average remaining lease term (in years)	5 years 2 months 12 days
Weighted-average discount rate	3.20%
Finance Leases
Right-of-use asset	$ 329
Current lease liabilities	18
Noncurrent lease liabilities	282
FInance lease liability	$ 300
Weighted-average remaining lease term (in years)	16 years
Weighted-average discount rate	4.70%
Right-of-use asset obtained in exchange for operating lease liability	$ 1,201
Right-of-use asset obtained in exchange for finance lease liability	$ 184
Upstream
Finance Leases
Capitalized leased assets		$ 818
Accumulated amortization		$ 617