Fair Value Measurement - Fair Value Level 3 Rollforward Recurring Basis (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Financial Guaranty Variable Interest Entities
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value at start of period	$ (715)	$ (289)	$ (333)
Total pretax realized and unrealized gains/(losses) recorded in:
Net income (loss)	34	(8)
Other comprehensive income (loss)	(3)	(1)
Issuances	0	0
Sales	0
Settlements	99	53
VIE consolidations	(571)	0
Deconsolidations	15
Fair value at end of period	715	289
Change in unrealized gains/(losses) related to financial instruments held	59	(6)
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)	(1)
Consolidated Investment Vehicles
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value at start of period	(4,154)	(3,705)	$ (1,227)
Total pretax realized and unrealized gains/(losses) recorded in:
Net income (loss)	178	15
Other comprehensive income (loss)	42	0
Issuances	(1,421)	(3,367)
Sales	2
Settlements	402	891
VIE consolidations	(26)	(17)
Deconsolidations	374
Fair value at end of period	4,154	3,705
Change in unrealized gains/(losses) related to financial instruments held	217	(2)
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	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	(154)	(100)
Total pre-tax realized and unrealized gains (losses) recorded in:
Net income (loss)	(11)	(58)
Other comprehensive income (loss)	0	0
Issuances	0	0
Sales	0
Settlements	3	(4)
Consolidations	0	0
Deconsolidations	0
Fair value at end of period	(162)	(154)
Change in unrealized gains/(losses)included in earnings related to financial instruments	(11)	(74)
Fixed-maturity securities \| Obligations of state and political subdivisions
Fair Value Level 3 Rollforward
Fair value at beginning of period	72	101
Total pretax realized and unrealized gains/(losses) recorded in:
Net income (loss)	1	23
Other comprehensive income (loss)	(12)	(5)
Purchases	0	0
Sales	0	(44)
Settlements	(14)	(3)
Consolidations	0	0
Deconsolidation	0
Fair value at end of period	47	72
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	(12)	1
Fixed-maturity securities \| RMBS
Fair Value Level 3 Rollforward
Fair value at beginning of period	216	255
Total pretax realized and unrealized gains/(losses) recorded in:
Net income (loss)	16	16
Other comprehensive income (loss)	(36)	(1)
Purchases	22	0
Sales	0	0
Settlements	(39)	(54)
Consolidations	0	0
Deconsolidation	0
Fair value at end of period	179	216
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	(32)	(1)
Fixed-maturity securities \| Asset-backed securities
Fair Value Level 3 Rollforward
Fair value at beginning of period	863	940
Total pretax realized and unrealized gains/(losses) recorded in:
Net income (loss)	5	18
Other comprehensive income (loss)	(47)	(5)
Purchases	43	344
Sales	(13)	(142)
Settlements	(57)	(292)
Consolidations	0	0
Deconsolidation	0
Fair value at end of period	794	863
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	(45)	(6)
Fixed-maturity securities \| Corporate securities
Fair Value Level 3 Rollforward
Fair value at beginning of period	0	30
Total pretax realized and unrealized gains/(losses) recorded in:
Net income (loss)		2
Other comprehensive income (loss)		16
Purchases		0
Sales		(48)
Settlements		0
Consolidations		0
Fair value at end of period		0
Fixed-maturity securities \| Corporate 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		0
Financial Guaranty Variable Interest Entities
Fair Value Level 3 Rollforward
Fair value at beginning of period	260	296
Total pretax realized and unrealized gains/(losses) recorded in:
Net income (loss)	(3)	26
Other comprehensive income (loss)	0	0
Purchases	0	0
Sales	0	0
Settlements	(60)	(62)
Consolidations	22	0
Deconsolidation	(15)
Fair value at end of period	204	260
Change in unrealized gains/(losses) related to financial instruments held, Included in OCI	(3)	27
Consolidated Investment Vehicles \| Corporate securities
Fair Value Level 3 Rollforward
Fair value at beginning of period	91	0
Total pretax realized and unrealized gains/(losses) recorded in:
Net income (loss)	2	0
Other comprehensive income (loss)	0	0
Purchases	16	0
Sales	(13)	0
Settlements	0	0
Consolidations	0	91
Deconsolidation	0
Fair value at end of period	96	91
Change in unrealized gains/(losses) related to financial instruments held, Included in OCI	1	0
Consolidated Investment Vehicles \| Equity securities and warrants
Fair Value Level 3 Rollforward
Fair value at beginning of period	239	2
Total pretax realized and unrealized gains/(losses) recorded in:
Net income (loss)	1	35
Other comprehensive income (loss)	0	0
Purchases	73	56
Sales	(16)	(28)
Settlements	0	0
Consolidations	0	174
Deconsolidation	0
Fair value at end of period	297	239
Change in unrealized gains/(losses) related to financial instruments held, Included in OCI	(8)	(2)
Consolidated Investment Vehicles \| Structured products
Fair Value Level 3 Rollforward
Fair value at beginning of period	0
Total pretax realized and unrealized gains/(losses) recorded in:
Net income (loss)	(5)
Other comprehensive income (loss)	0
Purchases	52
Sales	(21)
Settlements	0
Consolidations	0
Deconsolidation	20
Fair value at end of period	46	0
Change in unrealized gains/(losses) related to financial instruments held, Included in OCI	(4)
Other
Fair Value Level 3 Rollforward
Fair value at beginning of period	27	54
Total pretax realized and unrealized gains/(losses) recorded in:
Net income (loss)	24	(27)
Other comprehensive income (loss)	(1)	0
Purchases	0	0
Sales	0	0
Settlements	0	0
Consolidations	0	0
Deconsolidation	0
Fair value at end of period	50	27
Change in unrealized gains/(losses) related to financial instruments held, Included in OCI	24	$ (28)
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	$ (1)

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

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