Leases Assets and Liabilities, Lessee (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Dec. 31, 2018
Assets and Liabilities, Lessee [Abstract]
Finance Lease, Right-of-Use Asset, Amortization	$ 1	$ 1
Finance Lease, Interest Expense	0	$ 0
Operating Lease, Right-of-Use Asset	125		$ 0
Leases, Right of Use Asset	135
Operating Lease, Liability, Current	23		0
Operating Lease, Liability, Noncurrent	88		$ 0
Leases, Liability	$ 119