Financial Guaranty Variable Interest Entities and Consolidated Investment Vehicles - Schedule of Assets and Liabilities (Details) - USD ($) $ in Millions	6 Months Ended	12 Months Ended
	Jun. 30, 2022	Dec. 31, 2021
Variable Interest Entity [Line Items]
Assets	$ 16,960	$ 18,208
Liabilities	11,392	11,708
Variable Interest Entity, Primary Beneficiary | Fund investments: | Cash and cash equivalents
Variable Interest Entity [Line Items]
Assets	49	64
Variable Interest Entity, Primary Beneficiary | Fund investments: | Equity securities and warrants
Variable Interest Entity [Line Items]
Assets	394	252
Variable Interest Entity, Primary Beneficiary | Fund investments: | Obligations of state and political subdivisions
Variable Interest Entity [Line Items]
Assets	0	101
Variable Interest Entity, Primary Beneficiary | Fund investments: | Corporate securities
Variable Interest Entity [Line Items]
Assets	90	98
Variable Interest Entity, Primary Beneficiary | Fund investments: | Structured products
Variable Interest Entity [Line Items]
Assets	127	62
Variable Interest Entity, Primary Beneficiary | Fund investments: | Due from brokers and counterparties
Variable Interest Entity [Line Items]
Assets	6	49
Variable Interest Entity, Primary Beneficiary | Fund investments: | Other
Variable Interest Entity [Line Items]
Assets	0	1
Variable Interest Entity, Primary Beneficiary | CLOs and CLO warehouse assets: | Cash and cash equivalents
Variable Interest Entity [Line Items]
Assets	76	156
Variable Interest Entity, Primary Beneficiary | CLOs and CLO warehouse assets: | Due from brokers and counterparties
Variable Interest Entity [Line Items]
Assets	91	99
Variable Interest Entity, Primary Beneficiary | CLOs and CLO warehouse assets: | Loans in CLOs, FVO
Variable Interest Entity [Line Items]
Assets	4,160	3,913
Variable Interest Entity, Primary Beneficiary | CLOs and CLO warehouse assets: | Loans in CLO warehouses, FVO
Variable Interest Entity [Line Items]
Assets	233	331
Variable Interest Entity, Primary Beneficiary | CLOs and CLO warehouse assets: | Short-term investments
Variable Interest Entity [Line Items]
Assets	230	145
Variable Interest Entity, Primary Beneficiary | Assets of Consolidated Investment Vehicles
Variable Interest Entity [Line Items]
Assets	5,456	5,271
Variable Interest Entity, Primary Beneficiary | Assets of Consolidated Investment Vehicles | Investments in AssuredIM Funds and Other Affiliated Entities
Variable Interest Entity [Line Items]
Assets	358	223
Variable Interest Entity, Primary Beneficiary | Liabilities of CIVs
Variable Interest Entity [Line Items]
Liabilities	4,568	4,436
Variable Interest Entity, Primary Beneficiary | Liabilities of CIVs | CLO obligations of CFEs
Variable Interest Entity [Line Items]
Liabilities	$ 3,947	$ 3,665
CLO's weighted average maturity	6 years 8 months 12 days	6 years 7 months 6 days
CLO's weighted average interest rate	2.80%	1.80%
Variable Interest Entity, Primary Beneficiary | Liabilities of CIVs | Warehouse financing debt
Variable Interest Entity [Line Items]
Liabilities	$ 157	$ 126
CLO's weighted average maturity	1 year 2 months 12 days	1 year 9 months 18 days
CLO's weighted average interest rate	1.00%	1.10%
Variable Interest Entity, Primary Beneficiary | Liabilities of CIVs | Securities sold short, at fair value
Variable Interest Entity [Line Items]
Liabilities	$ 0	$ 41
Variable Interest Entity, Primary Beneficiary | Liabilities of CIVs | Due to brokers and counterparties
Variable Interest Entity [Line Items]
Liabilities	424	570
Variable Interest Entity, Primary Beneficiary | Liabilities of CIVs | Other liabilities
Variable Interest Entity [Line Items]
Liabilities	40	34
Variable Interest Entity, Primary Beneficiary | Consolidated Investment Vehicles, Meeting Voting Interest Entity Criteria
Variable Interest Entity [Line Items]
Assets	$ 60	$ 12