Basis of Presentation and Significant Accounting Policies Supplemental Cash Flow information (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Dec. 31, 2023	Dec. 31, 2022
Cash and Cash Equivalents, at Carrying Value	$ 33	$ 38
Income Taxes Paid	2	4
Restricted Cash	11	10	$ 12
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	296	304	274	$ 61
Securities acquired (transferred) in transactions related to Puerto Rico restructurings	0	(1)
Securities acquired (transferred) in connection with financial guarantee commutations	(65)
Long-term Debt [Member]
Interest Paid, Including Capitalized Interest, Operating and Investing Activities	0	50
Variable Interest Entity, Primary Beneficiary [Member]
Restricted Cash	$ 252	$ 256	$ 246