Summary of Significant Accounting Policies Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Net	$ 44	$ 17
Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment	69	82
Depreciation	9	13	$ 16
Amortization of Debt Issuance Costs	11	6	6
Credit Enhancement Fees	$ 1	$ 1	$ 1
Minimum
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Estimated Useful Lives	P3Y
Maximum
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Estimated Useful Lives	P10Y