Leases Assets and Liabilities, Lessee (Details) - USD ($) $ in Millions	Dec. 31, 2019	Sep. 30, 2019	Jan. 01, 2019	Dec. 31, 2018
Leases [Abstract]
Operating Lease, Right-of-Use Asset	$ 122		$ 105	$ 0
Finance Lease, Right-of-Use Asset	10
Leases, Right of Use Asset	132
Operating Lease, Liability, Current	22			0
Finance Lease, Liability, Current	4
Operating Lease, Liability, Noncurrent	86			$ 0
Finance Lease, Liability, Noncurrent	3
Leases, Liability	115
Favorable leasehold interest	14	$ 14
Finance lease, Accumulated Amortization	$ 1