Leases Supplemental Cash Flow Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Leases [Abstract]
Operating Lease, Payments	$ 8	$ 7
Finance Lease, Interest Payment on Liability	10	5
Finance Lease, Principal Payments	6	4
Right-of-Use Asset Obtained in Exchange for Operating Lease Liability	0	56
Right-of-Use Asset Obtained in Exchange for Finance Lease Liability	$ 0	$ 154