Segment Reporting (Details) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023 USD ($)	Sep. 30, 2022 USD ($)	Sep. 30, 2023 USD ($) level3FinancialInstruments	Sep. 30, 2022 USD ($)	Dec. 31, 2022 USD ($)
Segment Reporting, Revenue Reconciling Item [Line Items]
Number of Reportable Segments | level3FinancialInstruments			3
Revenues	$ 74	$ 80	$ 194	$ 286
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest	68	342	28	352
Provision for income taxes	1	2	7	4
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	66	340	21	348
Premiums Earned, Net	18	11	47	39
Net Investment Income	30	11	100	(6)
Amortization of Intangible Assets	7	6	21	34
Interest Expense	16	49	48
Total assets	7,847	9,412	7,847	9,412	$ 7,973
Premiums Written, Net	27	0	0	21
Derivative, Gain (Loss) on Derivative, Net	4	37	1	124
Net realized gains on extinguishment of debt	0	0	0	57
Insurance Commissions and Fees	15	7	39	22
Losses and loss adjustment expenses	(76)	(353)	(51)	(341)
Other Cost and Expense, Operating	49	31	120	88
Insurance Commissions	8	4	22	13
Depreciation	0	0	1	1
Benefits, Losses and Expenses	6	(262)	166	(66)
Net Income (Loss) Attributable to Nonredeemable Noncontrolling Interest	0	0	(1)	(1)
Net income attributable to common shareholders	66	340	19	347
Realized Investment Gains (Losses)	1	14	(7)	31
Contractually Specified Servicing Fee, Late Fee, and Ancillary Fee Earned in Exchange for Servicing Financial Asset	2	1	6	2
Other income Items	3	(1)	7	17
Deferred Policy Acquisition Costs, Amortization Expense	2	1	5	2
Financial Guarantee
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	41	67	112	250
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest	69	349	29	362
Premiums Earned, Net	6	7	20	31
Net Investment Income	27	9	90	(9)
Amortization of Intangible Assets	6	5	18	32
Interest Expense	16	49	48	138
Total assets	7,018	8,902	7,018	8,902
Derivative, Gain (Loss) on Derivative, Net	4	37	2	123
Net realized gains on extinguishment of debt			0	57
Losses and loss adjustment expenses	(86)	(356)	(71)	(347)
Other Cost and Expense, Operating	35	20	87	64
Depreciation	0	0	1	1
Benefits, Losses and Expenses	(28)	(282)	83	(112)
Realized Investment Gains (Losses)	1	14	(7)	31
Other income Items	3	(1)	7	17
Deferred Policy Acquisition Costs, Amortization Expense	0	0	0	0
Specialty Property & Casualty Program
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	16	6	35	11
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest	0	(1)	(1)	(5)
Premiums Earned, Net	12	4	27	8
Net Investment Income	1	0	3	1
Total assets	457	259	457	259
Losses and loss adjustment expenses	10	3	20	5
Other Cost and Expense, Operating	4	3	12	10
Depreciation	0	0	0	0
Benefits, Losses and Expenses	15	7	36	16
Realized Investment Gains (Losses)			0
Managing General Agency Underwriter
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	15	7	39	22
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest	2	1	7	3
Amortization of Intangible Assets	1	1	3	2
Total assets	160	94	160	94
Insurance Commissions and Fees	15	7	39	22
Other Cost and Expense, Operating	3	1	7	4
Insurance Commissions	8	4	22	13
Depreciation	0	0	0	0
Benefits, Losses and Expenses	12	6	33	19
Corporate and Other
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	3	1	7	2
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest	(4)	(6)	(8)	(8)
Net Investment Income	3	1	7	2
Total assets	213	157	213	157
Derivative, Gain (Loss) on Derivative, Net	0	0	0	1
Other Cost and Expense, Operating	7	6	14	11
Depreciation	0	0	0	0
Benefits, Losses and Expenses	7	6	14	11
Surplus Notes	0	69	0	69
Realized Investment Gains (Losses)	0	0	0	0
Other income Items	0	0	0	0
Property and Casualty, Commercial Insurance
Segment Reporting, Revenue Reconciling Item [Line Items]
Contractually Specified Servicing Fee, Late Fee, and Ancillary Fee Earned in Exchange for Servicing Financial Asset	2	1	6	2
Other income Items	0	0	0	0
Deferred Policy Acquisition Costs, Amortization Expense	2	1	5	1
Insurance Distribution
Segment Reporting, Revenue Reconciling Item [Line Items]
Other income Items	$ 0	$ 0	$ 0	$ 0