Financial Guaranty Variable Interest Entities and Consolidated Investment Vehicles - Schedule of Assets and Liabilities (Details) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2022	Dec. 31, 2021
Variable Interest Entity [Line Items]
Assets	$ 16,660	$ 18,208
Liabilities	11,486	11,708
Variable Interest Entity, Primary Beneficiary | Fund investments: | Cash and cash equivalents
Variable Interest Entity [Line Items]
Assets	71	64
Variable Interest Entity, Primary Beneficiary | Fund investments: | Equity securities and warrants
Variable Interest Entity [Line Items]
Assets	434	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	87	98
Variable Interest Entity, Primary Beneficiary | Fund investments: | Structured products
Variable Interest Entity [Line Items]
Assets	133	62
Variable Interest Entity, Primary Beneficiary | Fund investments: | Due from brokers and counterparties
Variable Interest Entity [Line Items]
Assets	0	49
Variable Interest Entity, Primary Beneficiary | Fund investments: | Other
Variable Interest Entity [Line Items]
Assets	1	1
Variable Interest Entity, Primary Beneficiary | CLOs and CLO warehouse assets: | Cash and cash equivalents
Variable Interest Entity [Line Items]
Assets	68	156
Variable Interest Entity, Primary Beneficiary | CLOs and CLO warehouse assets: | Due from brokers and counterparties
Variable Interest Entity [Line Items]
Assets	45	99
Variable Interest Entity, Primary Beneficiary | CLOs and CLO warehouse assets: | Loans in CLOs, FVO
Variable Interest Entity [Line Items]
Assets	4,088	3,913
Variable Interest Entity, Primary Beneficiary | CLOs and CLO warehouse assets: | Loans in CLO warehouses, FVO
Variable Interest Entity [Line Items]
Assets	324	331
Variable Interest Entity, Primary Beneficiary | CLOs and CLO warehouse assets: | Short-term investments
Variable Interest Entity [Line Items]
Assets	85	145
Variable Interest Entity, Primary Beneficiary | Assets of Consolidated Investment Vehicles
Variable Interest Entity [Line Items]
Assets	5,336	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	394	223
Variable Interest Entity, Primary Beneficiary | Liabilities of CIVs
Variable Interest Entity [Line Items]
Liabilities	4,447	4,436
Variable Interest Entity, Primary Beneficiary | Liabilities of CIVs | CLO obligations of CFEs
Variable Interest Entity [Line Items]
Liabilities	$ 3,962	$ 3,665
CLO's weighted average maturity	6 years 6 months	6 years 7 months 6 days
CLO's weighted average interest rate	3.90%	1.80%
Variable Interest Entity, Primary Beneficiary | Liabilities of CIVs | Warehouse financing debt
Variable Interest Entity [Line Items]
Liabilities	$ 224	$ 126
CLO's weighted average maturity	1 year 6 months	1 year 9 months 18 days
CLO's weighted average interest rate	2.60%	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	173	570
Variable Interest Entity, Primary Beneficiary | Liabilities of CIVs | Other liabilities
Variable Interest Entity [Line Items]
Liabilities	88	34
Variable Interest Entity, Primary Beneficiary | Consolidated Investment Vehicles, Meeting Voting Interest Entity Criteria
Variable Interest Entity [Line Items]
Assets	69	$ 12
Liabilities	$ 2