Segment Reporting (Details) $ in Millions	3 Months Ended
	Mar. 31, 2022 USD ($) level3FinancialInstruments	Mar. 31, 2021 USD ($)	Dec. 31, 2021 USD ($)
Segment Reporting, Revenue Reconciling Item [Line Items]
Number of Reportable Segments | level3FinancialInstruments	3
Revenues	$ 119	$ 129
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest	3	19
Provision (benefit) for income taxes	0	2
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	2	17
Premiums Earned, Net	15	14
Net investment income, including realized gains (loss)	5	49
Amortization of intangible assets	14	19
Interest Expense	44	50
Total assets	11,531	12,840	$ 12,303
Premiums Written, Net	12	(9)
Derivative, Gain (Loss) on Derivative, Net	57	25
Insurance Commissions and Fees	9	7
Other revenues, operating	34	33
Losses and loss expenses (benefit)	24	8
Operating Expenses	29	29
Insurance Commissions	5	4
Depreciation	0	0
Benefits, Losses and Expenses	116	110
Net Income (Loss) Attributable to Nonredeemable Noncontrolling Interest	0	0
Net income attributable to common shareholders	2	17
Financial Guarantee
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	109	118
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest	6	24
Premiums Earned, Net	13	14
Net investment income, including realized gains (loss)	5	49
Amortization of intangible assets	14	19
Interest Expense	44	50
Total assets	11,075	12,470
Derivative, Gain (Loss) on Derivative, Net	57	25
Other revenues, operating	34	29
Losses and loss expenses (benefit)	23	8
Operating Expenses	21	17
Depreciation	0	0
Benefits, Losses and Expenses	102	94
Specialty Property & Casualty Program
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	2	0
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest	(2)	(1)
Premiums Earned, Net	1	0
Net investment income, including realized gains (loss)	0	0
Total assets	191	108
Other revenues, operating	0	0
Losses and loss expenses (benefit)	1	0
Operating Expenses	3	1
Depreciation	0	0
Benefits, Losses and Expenses	4	1
Managing General Agency Underwriter
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	9	7
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest	2	2
Amortization of intangible assets	1	1
Total assets	97	98
Insurance Commissions and Fees	9	7
Other revenues, operating	0	0
Operating Expenses	1	1
Insurance Commissions	5	4
Depreciation	0	0
Benefits, Losses and Expenses	6	5
Corporate and Other
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	0	4
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest	(3)	(6)
Net investment income, including realized gains (loss)	0	0
Total assets	168	165
Other revenues, operating	0	4
Operating Expenses	3	10
Depreciation	0	0
Benefits, Losses and Expenses	3	10
Surplus Notes	$ 77	$ 114