Fair Value Measurement - Fair Value Level 3 Rollforward Recurring Basis (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Financial Guaranty Variable Interest Entities
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value at start of period	$ (554)	$ (715)	$ (289)
Total pretax realized and unrealized gains/(losses) recorded in:
Net income (loss)	2	34
Other comprehensive income (loss)	3	(3)
Issuances	0	0
Sales		0
Settlements	149	99
VIE consolidations		(571)
Deconsolidations	7	15
Fair value at end of period	554	715
Change in unrealized gains/(losses) related to financial instruments held	0	59
Financial Guaranty Variable Interest Entities \| Other Comprehensive Income (Loss)
Total pretax realized and unrealized gains/(losses) recorded in:
Change in unrealized gains/(losses) related to financial instruments held	3	(3)
Consolidated Investment Vehicles
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value at start of period	0	(4,154)	$ (3,705)
Total pretax realized and unrealized gains/(losses) recorded in:
Net income (loss)	(45)	178
Other comprehensive income (loss)	(13)	42
Issuances	0	(1,421)
Sales		2
Settlements	13	402
VIE consolidations		(26)
Deconsolidations	4,199	374
Fair value at end of period	0	4,154
Change in unrealized gains/(losses) related to financial instruments held	0	217
Consolidated Investment Vehicles \| Other Comprehensive Income (Loss)
Total pretax realized and unrealized gains/(losses) recorded in:
Change in unrealized gains/(losses) related to financial instruments held	0	42
Credit Risk Contract
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Fair value at beginning of period	(162)	(154)
Total pre-tax realized and unrealized gains (losses) recorded in:
Net income (loss)	114	(11)
Other comprehensive income (loss)	0	0
Issuances	(1)	0
Sales		0
Settlements	(1)	(3)
Consolidations		0
Deconsolidations	0	0
Fair value at end of period	(50)	(162)
Change in unrealized gains/(losses)included in earnings related to financial instruments	112	(11)
Fixed-maturity securities \| Obligations of state and political subdivisions
Fair Value Level 3 Rollforward
Fair value at beginning of period	47	72
Total pretax realized and unrealized gains/(losses) recorded in:
Net income (loss)	1	1
Other comprehensive income (loss)	(2)	(12)
Purchases	0	0
Sales	0	0
Settlements	(3)	(14)
Consolidation		0
Deconsolidations	0	0
Transfers into Level 3	3
Transfers out of Level 3	(40)
Fair value at end of period	6	47
Fixed-maturity securities \| Obligations of state and political subdivisions \| Other Comprehensive Income (Loss)
Total pretax realized and unrealized gains/(losses) recorded in:
Change in unrealized gains/(losses) related to financial instruments held, Included in OCI	0	(12)
Fixed-maturity securities \| RMBS
Fair Value Level 3 Rollforward
Fair value at beginning of period	179	216
Total pretax realized and unrealized gains/(losses) recorded in:
Net income (loss)	13	16
Other comprehensive income (loss)	(8)	(36)
Purchases	0	22
Sales	0	0
Settlements	(30)	(39)
Consolidation		0
Deconsolidations	0	0
Transfers into Level 3	0
Transfers out of Level 3	0
Fair value at end of period	154	179
Fixed-maturity securities \| RMBS \| Other Comprehensive Income (Loss)
Total pretax realized and unrealized gains/(losses) recorded in:
Change in unrealized gains/(losses) related to financial instruments held, Included in OCI	(7)	(32)
Fixed-maturity securities \| Asset-backed securities
Fair Value Level 3 Rollforward
Fair value at beginning of period	794	863
Total pretax realized and unrealized gains/(losses) recorded in:
Net income (loss)	32	5
Other comprehensive income (loss)	(8)	(47)
Purchases	23	43
Sales	(2)	(13)
Settlements	(36)	(57)
Consolidation		0
Deconsolidations	0	0
Transfers into Level 3	0
Transfers out of Level 3	0
Fair value at end of period	803	794
Fixed-maturity securities \| Asset-backed securities \| Other Comprehensive Income (Loss)
Total pretax realized and unrealized gains/(losses) recorded in:
Change in unrealized gains/(losses) related to financial instruments held, Included in OCI	9	(45)
Financial Guaranty Variable Interest Entities
Fair Value Level 3 Rollforward
Fair value at beginning of period	204	260
Total pretax realized and unrealized gains/(losses) recorded in:
Net income (loss)	9	(3)
Other comprehensive income (loss)	0	0
Purchases	0	0
Sales	0	0
Settlements	(33)	(60)
Consolidation		22
Deconsolidations	(7)	(15)
Transfers into Level 3	1
Transfers out of Level 3	0
Fair value at end of period	174	204
Change in unrealized gains/(losses) related to financial instruments held, Included in OCI	4	(3)
Consolidated Investment Vehicles \| Equity securities and warrants
Fair Value Level 3 Rollforward
Fair value at beginning of period	297	239
Total pretax realized and unrealized gains/(losses) recorded in:
Net income (loss)	51	1
Other comprehensive income (loss)	0	0
Purchases	42	73
Sales	(91)	(16)
Settlements	0	0
Consolidation		0
Deconsolidations	(219)	0
Transfers into Level 3	0
Transfers out of Level 3	0
Fair value at end of period	80	297
Change in unrealized gains/(losses) related to financial instruments held, Included in OCI	11	(8)
Consolidated Investment Vehicles \| Corporate securities
Fair Value Level 3 Rollforward
Fair value at beginning of period	96	91
Total pretax realized and unrealized gains/(losses) recorded in:
Net income (loss)	(3)	2
Other comprehensive income (loss)	0	0
Purchases	6	16
Sales	(15)	(13)
Settlements	0	0
Consolidation		0
Deconsolidations	(84)	0
Transfers into Level 3	0
Transfers out of Level 3	0
Fair value at end of period	0	96
Change in unrealized gains/(losses) related to financial instruments held, Included in OCI	0	1
Consolidated Investment Vehicles \| Structured products
Fair Value Level 3 Rollforward
Fair value at beginning of period	46	0
Total pretax realized and unrealized gains/(losses) recorded in:
Net income (loss)	21	(5)
Other comprehensive income (loss)	0	0
Purchases	5	52
Sales	(48)	(21)
Settlements	0	0
Consolidation		0
Deconsolidations	165	20
Transfers into Level 3	0
Transfers out of Level 3	0
Fair value at end of period	189	46
Change in unrealized gains/(losses) related to financial instruments held, Included in OCI	10	(4)
Other
Fair Value Level 3 Rollforward
Fair value at beginning of period	50	27
Total pretax realized and unrealized gains/(losses) recorded in:
Net income (loss)	(32)	24
Other comprehensive income (loss)	0	(1)
Purchases	0	0
Sales	0	0
Settlements	(4)	0
Consolidation		0
Deconsolidations	0	0
Transfers into Level 3	0
Transfers out of Level 3	0
Fair value at end of period	14	50
Change in unrealized gains/(losses) related to financial instruments held, Included in OCI	(32)	24
Other \| Other Comprehensive Income (Loss)
Total pretax realized and unrealized gains/(losses) recorded in:
Change in unrealized gains/(losses) related to financial instruments held, Included in OCI	$ 0	$ (1)

Fair Value, Measured with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Consolidation

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Amount of unrealized gain (loss) recognized in income from asset measured at fair value on recurring basis using unobservable input (level 3) and still held.

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Amount of purchases of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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Amount of settlement of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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Amount of gain (loss) recognized in income from derivative asset (liability) after deduction of derivative liability (asset), measured at fair value on recurring basis using unobservable input (level 3).

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