Leases (Schedule of Maturities of Operating and Financing Leases) (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Leases [Abstract]
Lessee, operating lease, liability, payments, due next twelve months	$ 147
Finance lease, liability, payments, due next twelve months	16
Lease liability, payments, due next twelve months	163
Lessee, operating lease, liability, payments, due year two	110
Finance lease, liability, payments, due year two	15
Lease liability, payments, due year two	125
Lessee, operating lease, liability, payments, due year three	75
Finance lease, liability, payments, due year three	14
Lease liability, payments due, year three	89
Lessee, operating lease, liability, payments, due year four	42
Finance lease, liability, payments, due year four	13
Lease liability, payments, due year four	55
Lessee, operating lease, liability, payments, due year five	24
Finance lease, liability, payments, due year five	10
Lease liability, payments, due year five	34
Lessee, operating lease, liability, payments, due after year five	103
Finance lease, liability, payments, due after year five	66
Lease liability payments, due after year five	169
Operating lease, liability, payment, due	501
Finance lease, liability, payment, due	134
Lease liability, payments, total	635
Lessee, operating lease, liability, undiscounted excess amount	63
Lessee, finance lease, liability, undiscounted excess amount	34
Lease liability, undiscounted excess amount	97
Operating lease liability	438
Finance lease liability	100	$ 63
Lease liability total	$ 538