Basis of Presentation and Significant Accounting Policies Supplemental Cash Flow Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Aug. 03, 2018
Income Taxes Paid	$ 11	$ 21	$ 35
AMPS Exchange Carrying Value of Surplus Notes Issued				$ 187
Non Cash Exchange of Puerto Rico Bonds		510
Non Cash Impact of Rehabilitation Exit Transaction			1,919
Cash and cash equivalents	20	24	63
Restricted Cash	13	55	19
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	35	81	83
Long-term Debt [Member]
Interest Paid, Including Capitalized Interest, Operating and Investing Activities	$ 107	$ 143	$ 232