Financial Guaranty Variable Interest Entities and Consolidated Investment Vehicles - Schedule of Assets and Liabilities of Consolidated Investment Vehicles (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Variable Interest Entity [Line Items]
Total assets	$ 16,843	$ 18,208
Total liabilities	11,551	11,708
Variable Interest Entity, Primary Beneficiary | Consolidated Investment Vehicles
Variable Interest Entity [Line Items]
Total liabilities	4,625	4,436
Variable Interest Entity, Primary Beneficiary | CLO obligations of CFEs | Consolidated Investment Vehicles
Variable Interest Entity [Line Items]
Total liabilities	4,090	3,665
Variable Interest Entity, Primary Beneficiary | Warehouse financing debt | Consolidated Investment Vehicles
Variable Interest Entity [Line Items]
Total liabilities	313	126
Variable Interest Entity, Primary Beneficiary | Securities sold short, at fair value | Consolidated Investment Vehicles
Variable Interest Entity [Line Items]
Total liabilities	0	41
Variable Interest Entity, Primary Beneficiary | Due to brokers and counterparties | Consolidated Investment Vehicles
Variable Interest Entity [Line Items]
Total liabilities	112	570
Variable Interest Entity, Primary Beneficiary | Other liabilities | Consolidated Investment Vehicles
Variable Interest Entity [Line Items]
Total liabilities	110	34
Variable Interest Entity, Primary Beneficiary | Consolidated Investment Vehicles
Variable Interest Entity [Line Items]
Total assets	5,493	5,271
Variable Interest Entity, Primary Beneficiary | Consolidated Investment Vehicles | Investments in AssuredIM Funds and Other Affiliated Entities
Variable Interest Entity [Line Items]
Total assets	$ 392	$ 223
Variable Interest Entity, Primary Beneficiary | Consolidated Investment Vehicles | CLO obligations of CFEs
Variable Interest Entity [Line Items]
CLOs, weighted average maturity	6 years 2 months 12 days	6 years 7 months 6 days
CLOs, weighted average interest rate	5.30%	1.80%
Variable Interest Entity, Primary Beneficiary | Consolidated Investment Vehicles | Warehouse financing debt
Variable Interest Entity [Line Items]
CLOs, weighted average maturity	1 year 10 months 24 days	1 year 9 months 18 days
CLOs, weighted average interest rate	4.50%	1.10%
Variable Interest Entity, Primary Beneficiary | Consolidated Investment Vehicles | Fund Investments | Cash and cash equivalents
Variable Interest Entity [Line Items]
Total assets	$ 59	$ 64
Variable Interest Entity, Primary Beneficiary | Consolidated Investment Vehicles | Fund Investments | Due from brokers and counterparties
Variable Interest Entity [Line Items]
Total assets	0	49
Variable Interest Entity, Primary Beneficiary | Consolidated Investment Vehicles | Fund Investments | Other
Variable Interest Entity [Line Items]
Total assets	1	1
Variable Interest Entity, Primary Beneficiary | Consolidated Investment Vehicles | Fund Investments | Equity securities and warrants
Variable Interest Entity [Line Items]
Total assets	434	252
Variable Interest Entity, Primary Beneficiary | Consolidated Investment Vehicles | Fund Investments | Obligations of state and political subdivisions
Variable Interest Entity [Line Items]
Total assets	0	101
Variable Interest Entity, Primary Beneficiary | Consolidated Investment Vehicles | Fund Investments | Structured products
Variable Interest Entity [Line Items]
Total assets	128	62
Variable Interest Entity, Primary Beneficiary | Consolidated Investment Vehicles | Fund Investments | Corporate securities
Variable Interest Entity [Line Items]
Total assets	96	98
Variable Interest Entity, Primary Beneficiary | Consolidated Investment Vehicles | CLOs | Cash and cash equivalents
Variable Interest Entity [Line Items]
Total assets	38	156
Variable Interest Entity, Primary Beneficiary | Consolidated Investment Vehicles | CLOs | Due from brokers and counterparties
Variable Interest Entity [Line Items]
Total assets	32	99
Variable Interest Entity, Primary Beneficiary | Consolidated Investment Vehicles | CLOs | Loans in CLOs, FVO
Variable Interest Entity [Line Items]
Total assets	4,202	3,913
Variable Interest Entity, Primary Beneficiary | Consolidated Investment Vehicles | CLOs | Loans in CLO warehouses, FVO
Variable Interest Entity [Line Items]
Total assets	368	331
Variable Interest Entity, Primary Beneficiary | Consolidated Investment Vehicles | CLOs | Short-term investments
Variable Interest Entity [Line Items]
Total assets	135	145
Voting Interest Entity | Consolidated Investment Vehicles
Variable Interest Entity [Line Items]
Total liabilities	1
Voting Interest Entity | Consolidated Investment Vehicles | Investments
Variable Interest Entity [Line Items]
Total assets	$ 58	$ 12