Consolidated Statements of Cash Flows - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Cash flows from operating activities:
Net income (loss) attributable to common stockholders	$ (17)	$ (437)	$ (216)
Net income (loss)	(16)	(437)	(216)
Adjustments to reconcile net income to net cash used in operating activities:
Depreciation and amortization	2	1	0
Amortization of bond premium and discount	(13)	(15)	(63)
Share-based compensation	14	11	12
Deferred income taxes	6	(9)	1
Current income taxes	(4)	17	35
Unearned premiums, net	(82)	(48)	(132)
Losses and loss expenses, net	(147)	76	(364)
Ceded premiums payable	6	(3)	(4)
Premium receivables	48	44	77
Accrued interest payable	103	93	87
Amortization of intangible assets	55	57	295
Net realized investment gains	(7)	(22)	(81)
Net realized gains (losses) on extinguishment of debt	(33)	0	0
Other, net	(35)	59	79
Net cash used in operating activities	(131)	(175)	(311)
Cash flows from investing activities:
Proceeds from sales of bonds	236	1,109	1,212
Proceeds from matured bonds	698	137	379
Purchases of bonds	(343)	(975)	(959)
Proceeds from sales of other invested assets	39	374	81
Purchases of other invested assets	(127)	(475)	(137)
Change in short-term investments	98	158	(218)
Change in cash collateral receivable	9	0	100
Proceeds From Financial Guaranty Variable Interest Entity Assets	171	178	543
Payments to Acquire Businesses, Net of Cash Acquired		(74)
Other, net	(5)	1	(2)
Net cash provided by investing activities	776	432	1,000
Cash flows from financing activities:
Proceeds from Sale of Senior Surplus Notes	11	0	0
Paydown of Ambac Note	(1,641)	(121)	(178)
Payments of Debt Issuance Costs	(12)	0	0
Payment, Tax Withholding, Share-based Payment Arrangement	(6)	(3)	(3)
Paydown of Financial Guaranty Variable Interest Entity Liabilities	(170)	(178)	(542)
Net Cash Provided by (Used in) Financing Activities	(657)	(303)	(691)
Effect of Exchange Rate on Cash and Cash Equivalents	0	0	0
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Excluding Exchange Rate Effect	(12)	(46)	(2)
Cash and cash equivalents end of period	17	20	24
Supplemental disclosure of cash flow information
Income Taxes Paid	15	11	21
Cash payments related to reorganization items:
Variable interest entity activities	(7)	(5)	(38)
Increase (Decrease) in Derivative Assets and Liabilities	(23)	6	(1)
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	23	35	81
Proceeds From Issuance of Ambac UK Debt	0	0	12
Proceeds from Issuance of Secured Debt	1,163
Net Income (Loss) Attributable to Nonredeemable Noncontrolling Interest	(1)
Proceeds from (Payments to) Noncontrolling Interests	(1)
Ambac Financial Group, Inc Parent Company Only [Member]
Cash flows from operating activities:
Net income (loss) attributable to common stockholders	(17)	(437)	(216)
Net income (loss)	(17)	(437)	(216)
Adjustments to reconcile net income to net cash used in operating activities:
Amortization of bond premium and discount	(9)	(6)	(6)
Share-based compensation	14	11	12
Current income taxes	1	30	15
Net realized investment gains	5	1	2
Other, net	(6)	(10)	(6)
Net cash used in operating activities	(10)	11	16
Cash flows from investing activities:
Proceeds from matured bonds	33	46	86
Purchases of bonds	(34)	(45)	(2)
Proceeds from sales of other invested assets	(8)	0	0
Change in short-term investments	105	89	(125)
Payments to Acquire Businesses, Net of Cash Acquired		(74)
Net cash provided by investing activities	95	16	(22)
Cash flows from financing activities:
Net Cash Provided by (Used in) Financing Activities	(92)	(29)	0
Cash and cash equivalents end of period	1	7	9
Supplemental disclosure of cash flow information
Income Taxes Paid	$ 0	$ 0	$ 1