Investments and Cash - Investment Portfolio Carrying Value (Details) - USD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021
Schedule of Cost-method Investments [Line Items]
Fixed-maturity securities, available-for-sale:	$ 7,119	$ 8,202
Fixed-maturity securities, trading, at fair value	303	0
Short-term investments, at fair value	810	1,225
Other invested assets	133	181
Total investments	8,365	9,608
Recovery Bonds
Schedule of Cost-method Investments [Line Items]
Fixed-maturity securities, available-for-sale:	358	0
Externally managed
Schedule of Cost-method Investments [Line Items]
Fixed-maturity securities, available-for-sale:	5,519	6,843
Loss Mitigation Securities and other
Schedule of Cost-method Investments [Line Items]
Fixed-maturity securities, available-for-sale:	705	818
AssuredIM managed
Schedule of Cost-method Investments [Line Items]
Fixed-maturity securities, available-for-sale:	$ 537	$ 541
BIG
Schedule of Cost-method Investments [Line Items]
Fixed-maturity securities rated as BIG	7.40%	7.50%
Not Internally Rated
Schedule of Cost-method Investments [Line Items]
Fixed-maturity securities rated as BIG	5.90%	0.90%
Equity method investments
Schedule of Cost-method Investments [Line Items]
Other invested assets	$ 123	$ 169
Other
Schedule of Cost-method Investments [Line Items]
Other invested assets	$ 10	$ 12

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