Leases Maturities of Lease Liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Leases [Abstract]
Operating Leases, Future Minimum Payments Due, Next Twelve Months	$ 8
Lessee, Operating Lease, Liability, Payments, Due Year Two	8
Lessee, Operating Lease, Liability, Payments, Due Year Three	8
Lessee, Operating Lease, Liability, Payments, Due Year Four	7
Lessee, Operating Lease, Liability, Payments, Due Year Five	1
Lessee, Operating Lease, Liability, Payments, Due after Year Five	45
Lessee, Operating Lease, Liability, Payments, Due	77
Lessee, Operating Lease, Liability, Undiscounted Excess Amount	(33)
Operating Lease, Liability	44	$ 51
Finance Lease, Liability, Payments, Due Year One	16
Finance Lease, Liability, Payments, Due Year Two	16
Finance Lease, Liability, Payments, Due Year Three	14
Finance Lease, Liability, Payments, Due Year Four	14
Finance Lease, Liability, Payments, Due Year Five	13
Finance Lease, Liability, Payments, Due after Year Five	222
Finance Lease, Liability, Payment, Due	295
Finance Lease, Liability, Undiscounted Excess Amount	(150)
Finance Lease, Liability	$ 145	$ 151