Leases Schedule of Payments due under operating leases net of sublease amounts and non-cancellable future rentals (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Schedule Of Maturities Of Operating Leases [Abstract]
Lessee, Operating Lease, Liability, Payments, Due Next Rolling Twelve Months	$ 287
Lessee, Operating Lease, Liability, Payments, Due in Rolling Year Two	235
Lessee, Operating Lease, Liability, Payments, Due in Rolling Year Three	194
Lessee, Operating Lease, Liability, Payments, Due in Rolling Year Four	151
Lessee, Operating Lease, Liability, Payments, Due in Rolling Year Five	98
Lessee, Operating Lease, Liability, Payments, Due after Rolling Year Five	609
Lessee, Operating Lease, Liability, Payments, Due	$ 1,574
Operating Leases, Future Minimum Payments Due, Next Twelve Months		$ 272
Operating Leases, Future Minimum Payments, Due in Two Years		232
Operating Leases, Future Minimum Payments, Due in Three Years		194
Operating Leases, Future Minimum Payments, Due in Four Years		165
Operating Leases, Future Minimum Payments, Due in Five Years		126
Operating Leases, Future Minimum Payments, Due Thereafter		849
Operating Leases, Future Minimum Payments Due		$ 1,838