Variable Interest Entities Special Purpose Entities, including Variable Interest Entities - Summary of Assets and Liabilities (Details) $ in Millions	Sep. 30, 2022 USD ($) Entity	Dec. 31, 2021 USD ($) Entity	Sep. 30, 2021 USD ($)
Debt Securities, Available-for-sale, Amortized Cost	$ 2,060
Fixed maturity securities, at fair value	1,977
Restricted Cash	6	$ 5	$ 6
Derivative assets	28	76
Other assets	85	68
Total assets	9,412	12,303	12,228
Interest Payable	576	576
Long-term debt	2,201	2,230
Derivative Liability	40	95
Other Liabilities	244	133
Liabilities	8,324	11,187
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	33	141
Ambac Assurance [Member] | Sitka AAC Note
Long-term debt	87	0
Ambac Assurance Corporation [Member] | Sitka AAC Note
Long-term debt	1,157	1,154
Variable Interest Entity, Primary Beneficiary [Member]
Fixed maturity securities, at fair value	2,119	3,455
Restricted Cash	2	2	$ 2
Financing Receivable, after Allowance for Credit Loss	1,682	2,718
Derivative assets	60	38
Other assets	1	2
Total assets	3,864	6,216
Long-term debt	2,603	4,056
Long-term Debt, at par less amortized discount	149	160
Long-term debt	2,752	4,216
Derivative Liability	1,110	1,940
Liabilities	3,862	6,156
Variable Interest Entity, Primary Beneficiary [Member] | Corporate Debt Securities [Member]
Fixed maturity securities, at fair value	2,026	3,320
Variable Interest Entity, Primary Beneficiary [Member] | Municipal Bonds [Member]
Debt Securities, Available-for-sale, Amortized Cost	98	106
Fixed maturity securities, at fair value	92	136
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	0	29
Variable Interest Entity, Primary Beneficiary [Member] | Ambac UK [Member]
Fixed maturity securities, at fair value	2,026	3,320
Restricted Cash	1	1
Financing Receivable, after Allowance for Credit Loss	1,682	2,718
Derivative assets	60	38
Other assets	0	0
Total assets	3,769	6,077
Long-term debt	2,603	4,056
Long-term Debt, at par less amortized discount	0	0
Long-term debt	2,603	4,056
Derivative Liability	1,110	1,940
Liabilities	3,713	5,996
Variable Interest Entity, Primary Beneficiary [Member] | Ambac UK [Member] | Corporate Debt Securities [Member]
Fixed maturity securities, at fair value	2,026	3,320
Variable Interest Entity, Primary Beneficiary [Member] | Ambac UK [Member] | Municipal Bonds [Member]
Fixed maturity securities, at fair value	0	0
Variable Interest Entity, Primary Beneficiary [Member] | Ambac Assurance [Member]
Fixed maturity securities, at fair value	92	136
Restricted Cash	1	1
Financing Receivable, after Allowance for Credit Loss	0	0
Derivative assets	0	0
Other assets	1	2
Total assets	95	139
Long-term debt	0	0
Long-term Debt, at par less amortized discount	149	160
Long-term debt	149	160
Derivative Liability	0	0
Liabilities	149	160
Variable Interest Entity, Primary Beneficiary [Member] | Ambac Assurance [Member] | Corporate Debt Securities [Member]
Fixed maturity securities, at fair value	0	0
Variable Interest Entity, Primary Beneficiary [Member] | Ambac Assurance [Member] | Municipal Bonds [Member]
Fixed maturity securities, at fair value	$ 92	$ 136
Consolidated Entities [Member]
Number Of Consolidated Variable Interest Entities | Entity	8	6
Consolidated Entities [Member] | Ambac UK [Member]
Number Of Consolidated Variable Interest Entities | Entity	5	5
Consolidated Entities [Member] | Ambac Assurance [Member]
Number Of Consolidated Variable Interest Entities | Entity	3	1