Financial Guarantee Insurance Contracts - Summary of Gross Premium Receivable Roll-Forward (Direct and Assumed Contracts) (Details) - USD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021
Premiums Receivable, Gross	$ 259	$ 329
Public Finance [Member]
Premiums Receivable, Gross	150	159
Housing Revenue [Member] | Public Finance [Member]
Premiums Receivable, Gross	148	157
Surveillance Category One [Member]
Premiums Receivable, Gross	217	277
Surveillance Category One [Member] | Public Finance [Member]
Premiums Receivable, Gross	142	151
Surveillance Category One [Member] | Housing Revenue [Member] | Public Finance [Member]
Premiums Receivable, Gross	$ 140	$ 149