Consolidated Balance Sheets - USD ($) $ in Millions	3 Months Ended	6 Months Ended
	Jun. 30, 2023	Jun. 30, 2023	Dec. 31, 2022	Dec. 31, 2021
Assets:
Fixed maturity securities, at fair value	$ 1,953	$ 1,953
Total investments (net of allowance for credit losses of $1 and $0)	2,510	2,510	$ 2,593
Restricted Cash	10	10	14
Premiums Receivable, Net	276	276	269
Premium Receivable, Allowance for Credit Loss	5	5	5
Reinsurance Recoverables, Including Reinsurance Premium Paid	149	149	115
Deferred ceded premium	198	198	124
Subrogation recoverable	139	139	271
Derivative assets	26	26	27
Intangible assets	317	317	326
Goodwill	61	61	61	$ 46
Other assets	89	89	84
Total assets	8,132	8,132	7,973
Liabilities:
Unearned premiums	394	394	372
Loss and loss expense reserves	863	863	805
Ceded premiums payable	96	96	39
Long-term debt	501	501	639
Accrued interest payable	450	450	427
Derivative Liability	37	37	38
Other liabilities	136	136	163
Total liabilities	6,809	6,809	6,647
Redeemable Noncontrolling Interest, Equity, Carrying Amount	20	20	20	18
Liabilities	6,809	6,809	6,647
Stockholders’ equity:
Preferred stock, par value $0.01 per share; 20,000,000 shares authorized; issued and outstanding shares—none	0	0	0
Common Stock, Value, Issued	0	0	0
Additional paid-in capital	283	283	274
Accumulated other comprehensive income	(209)	(209)	(253)	58
Retained earnings	1,191	1,191	1,245
Treasury stock, shares at cost: 0 and 8,202	(15)	(15)	(15)
Total Ambac Financial Group, Inc. stockholders’ equity	1,250	1,250	1,252
Noncontrolling interest	53	53	53
Total stockholders’ equity	1,303	1,303	1,305	1,098
Total liabilities and stockholders’ equity	8,132	8,132	7,973
Debt Securities, Available-for-sale, Allowance for Credit Loss	1	1	0
Debt Securities, Available-for-sale, Amortized Cost	2,033	2,033	2,041
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	309	309	61	$ 23
Deferred Policy Acquisition Cost	4	4	3
Capitalized Contract Cost, Net	$ 6	$ 6	$ 5
Treasury Stock, Common, Shares	1,355,146	1,355,146	1,685,233
Afg [Member]
Stockholders’ equity:
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	$ 43	$ 43	$ 44
Xchange
Liabilities:
Redeemable Noncontrolling Interest, Equity, Redemption Value	20	20
Redeemable Noncontrolling Interest, Equity, Carrying Amount			20
Short-term Investments [Member]
Assets:
Fixed maturity securities, at fair value	365	365	507
Stockholders’ equity:
Debt Securities, Available-for-sale, Allowance for Credit Loss	0	0	0
Debt Securities, Available-for-sale, Amortized Cost	365	365	507
Variable Interest Entity, Primary Beneficiary [Member]
Assets:
Fixed maturity securities, at fair value	2,056	2,056	1,967
Restricted Cash	266	266	17
Derivative assets	224	224	239
Other assets	2	2	2
Total assets	4,320	4,320	4,054
Liabilities:
Long-term debt	2,956	2,956	3,107
Derivative Liability	1,106	1,106	1,048
Other Sundry Liabilities, Current	264	264
Other liabilities	1	1	5
Total liabilities	4,326	4,326	4,160
Liabilities	4,326	4,326	4,160
Stockholders’ equity:
Financing Receivable, after Allowance for Credit Loss	1,772	1,772	1,829
Gross Investment Income, Operating	3
Derivative and other assets	226	226	241
Fixed Income Securities [Member]
Assets:
Fixed maturity securities, at fair value	1,552	1,552	1,395
Stockholders’ equity:
Debt Securities, Available-for-sale, Allowance for Credit Loss	1	1	0
Debt Securities, Available-for-sale, Amortized Cost	1,632	1,632	1,469
Debt Securities, Available-for-Sale, Excluding Accrued Interest	1,552	1,552	1,395
Debt Securities, Available-for-Sale, Amortized Cost, Excluding Accrued Interest, before Allowance for Credit Loss	1,631	1,631	1,469
Short-term Investments [Member]
Assets:
Fixed maturity securities, at fair value	365	365	507
Stockholders’ equity:
Gross Investment Income, Operating	5	10
Other Investments [Member]
Stockholders’ equity:
Other Investment Not Readily Marketable, Fair Value	530	530	568
Gross Investment Income, Operating	9	22
Fixed Income Securities, Trading
Stockholders’ equity:
Gross Investment Income, Operating	4	5
Debt Securities, Available-for-Sale, Excluding Accrued Interest	28	28	59
Collateral Pledged [Member] | Fixed Income Securities [Member]
Assets:
Fixed maturity securities, at fair value	36	36	64
Collateral Pledged [Member] | Fixed Income Securities [Member] | Short-term Investments [Member]
Assets:
Fixed maturity securities, at fair value	36	36	64
Stockholders’ equity:
Debt Securities, Available-for-sale, Allowance for Credit Loss	0	0	0
Debt Securities, Available-for-sale, Amortized Cost	36	36	64
Collateral Pledged [Member] | Short-term Investments
Stockholders’ equity:
Debt Securities, Available-for-sale, Amortized Cost	36	36	64
Collateralized Securities | Short-term Investments [Member]
Assets:
Fixed maturity securities, at fair value	$ 36	$ 36	$ 64