Variable Interest Entities Special Purpose Entities, including Variable Interest Entities - Summary of Assets and Liabilities (Details) $ in Millions	Jun. 30, 2022 USD ($) Entity	Dec. 31, 2021 USD ($) Entity	Jun. 30, 2021 USD ($)
Debt Securities, Available-for-sale, Amortized Cost	$ 1,979
Fixed maturity securities, at fair value	1,947
Restricted Cash	5	$ 5	$ 17
Derivative assets	40	76
Other assets	83	68
Total assets	10,061	12,303	12,907
Interest Payable	559	576
Long-term debt	2,189	2,230
Derivative Liability	61	95
Other Liabilities	124	133
Liabilities	9,198	11,187
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	39	141
Ambac Assurance Corporation [Member] | Sitka AAC Note
Long-term debt	1,156	1,154
Variable Interest Entity, Primary Beneficiary [Member]
Fixed maturity securities, at fair value	2,642	3,455
Restricted Cash	2	2	$ 2
Financing Receivable, after Allowance for Credit Loss	2,144	2,718
Derivative assets	51	38
Other assets	2	2
Total assets	4,841	6,216
Long-term debt	3,184	4,056
Long-term Debt, at par less amortized discount	155	160
Long-term debt	3,340	4,216
Derivative Liability	1,476	1,940
Liabilities	4,816	6,156
Variable Interest Entity, Primary Beneficiary [Member] | Corporate Debt Securities [Member]
Fixed maturity securities, at fair value	2,533	3,320
Variable Interest Entity, Primary Beneficiary [Member] | Municipal Bonds [Member]
Debt Securities, Available-for-sale, Amortized Cost	103	106
Fixed maturity securities, at fair value	109	136
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	6	29
Variable Interest Entity, Primary Beneficiary [Member] | Ambac UK [Member]
Fixed maturity securities, at fair value	2,533	3,320
Restricted Cash	1	1
Financing Receivable, after Allowance for Credit Loss	2,144	2,718
Derivative assets	51	38
Other assets	0	0
Total assets	4,728	6,077
Long-term debt	3,184	4,056
Long-term Debt, at par less amortized discount	0	0
Long-term debt	3,184	4,056
Derivative Liability	1,476	1,940
Liabilities	4,661	5,996
Variable Interest Entity, Primary Beneficiary [Member] | Ambac UK [Member] | Corporate Debt Securities [Member]
Fixed maturity securities, at fair value	2,533	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	109	136
Restricted Cash	1	1
Financing Receivable, after Allowance for Credit Loss	0	0
Derivative assets	0	0
Other assets	2	2
Total assets	113	139
Long-term debt	0	0
Long-term Debt, at par less amortized discount	155	160
Long-term debt	155	160
Derivative Liability	0	0
Liabilities	156	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	$ 109	$ 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