Segment Reporting (Details) $ in Millions	3 Months Ended
	Mar. 31, 2023 USD ($) level3FinancialInstruments	Mar. 31, 2022 USD ($)	Dec. 31, 2022 USD ($)
Segment Reporting, Revenue Reconciling Item [Line Items]
Number of Reportable Segments | level3FinancialInstruments	3
Revenues	$ 58	$ 119
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest	(29)	3
Provision for income taxes	4	0
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	(33)	2
Premiums Earned, Net	14	15
Net Investment Income	34	5
Amortization of Intangible Assets	7	14
Interest Expense	16	44
Total assets	8,219	11,531	$ 7,973
Premiums Written, Net	18	12
Derivative, Gain (Loss) on Derivative, Net	(4)	57
Insurance Commissions and Fees	14	9
Losses and loss adjustment expenses	18	24
Other Cost and Expense, Operating	36	29
Insurance Commissions	8	5
Depreciation	0	0
Benefits, Losses and Expenses	86	116
Net Income (Loss) Attributable to Nonredeemable Noncontrolling Interest	(1)	0
Net income attributable to common shareholders	(33)	2
Realized Investment Gains (Losses)	(4)	10
Contractually Specified Servicing Fee, Late Fee, and Ancillary Fee Earned in Exchange for Servicing Financial Asset	1	0
Other income Items	2	24
Deferred Policy Acquisition Costs, Amortization Expense	1	0
Financial Guarantee
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	32	109
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest	(32)	6
Premiums Earned, Net	7	13
Net Investment Income	31	5
Amortization of Intangible Assets	6	14
Interest Expense	16	44
Total assets	7,503	11,075
Derivative, Gain (Loss) on Derivative, Net	(3)	57
Losses and loss adjustment expenses	13	23
Other Cost and Expense, Operating	28	21
Depreciation	0	0
Benefits, Losses and Expenses	64	102
Realized Investment Gains (Losses)	(4)	10
Other income Items	2	24
Deferred Policy Acquisition Costs, Amortization Expense	0	0
Specialty Property & Casualty Program
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	9	2
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest	(1)	(2)
Premiums Earned, Net	7	1
Net Investment Income	1	0
Total assets	349	191
Losses and loss adjustment expenses	5	1
Other Cost and Expense, Operating	4	3
Depreciation	0	0
Benefits, Losses and Expenses	10	4
Managing General Agency Underwriter
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	15	9
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest	4	2
Amortization of Intangible Assets	1	1
Total assets	140	97
Insurance Commissions and Fees	14	9
Other Cost and Expense, Operating	2	1
Insurance Commissions	8	5
Depreciation	0	0
Benefits, Losses and Expenses	11	6
Corporate and Other
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	2	0
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest	0	(3)
Net Investment Income	2	0
Total assets	227	168
Derivative, Gain (Loss) on Derivative, Net	0
Other Cost and Expense, Operating	2	3
Depreciation	0	0
Benefits, Losses and Expenses	2	3
Surplus Notes	0	77
Realized Investment Gains (Losses)	0	0
Other income Items	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	1	0
Other income Items	0	0
Deferred Policy Acquisition Costs, Amortization Expense	1	0
Insurance Distribution
Segment Reporting, Revenue Reconciling Item [Line Items]
Other income Items	$ 0	$ 0