Leases (Schedule of Maturities of Operating and Financing Leases) (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Leases [Abstract]
Lessee, operating lease, liability, payments, due next twelve months	$ 158
Finance lease, liability, payments, due next twelve months	17
Lease liability, payments, due next twelve months	175
Lessee, operating lease, liability, payments, due year two	117
Finance lease, liability, payments, due year two	16
Lease liability, payments, due year two	133
Lessee, operating lease, liability, payments, due year three	74
Finance lease, liability, payments, due year three	14
Lease liability, payments due, year three	88
Lessee, operating lease, liability, payments, due year four	42
Finance lease, liability, payments, due year four	11
Lease liability, payments, due year four	53
Lessee, operating lease, liability, payments, due year five	26
Finance lease, liability, payments, due year five	10
Lease liability, payments, due year five	36
Lessee, operating lease, liability, payments, due after year five	105
Finance lease, liability, payments, due after year five	56
Lease liability payments, due after year five	161
Operating lease, liability, payment, due	522
Finance lease, liability, payment, due	124
Lease liability, payments, total	646
Lessee, operating lease, liability, undiscounted excess amount	59
Lessee, finance lease, liability, undiscounted excess amount	29
Lease liability, undiscounted excess amount	88
Operating lease liability	463
Finance lease liability	95	$ 100
Lease liability total	$ 558	$ 538