Leases Lease Cost (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2019
Leases [Abstract]
Operating Lease, Expense	$ 5	$ 109
Short-term Lease, Cost	5	91
Finance Lease, Right-of-Use Asset, Amortization	1	11
Sublease Income	(1)	(6)
Lease, Cost	$ 10	$ 205