Consolidated Balance Sheets $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2022 USD ($)	Jun. 30, 2022 USD ($)	Dec. 31, 2021 USD ($)
Assets:
Fixed maturity securities, at fair value	$ 1,947,000	$ 1,947,000
Total investments (net of allowance for credit losses of $0 and $0)	2,547,000	2,547,000	$ 2,955,000
Cash and cash equivalents	32,000	32,000	17,000
Restricted Cash	5,000	5,000	5,000
Premiums Receivable, Net	311,000	311,000	323,000
Premium Receivable, Allowance for Credit Loss	6,000	6,000	9,000
Reinsurance Recoverable, Allowance for Credit Loss	48	48	10
Reinsurance Recoverables, Including Reinsurance Premium Paid	55,000	55,000	55,000
Deferred ceded premium	104,000	104,000	90,000
Subrogation recoverable	1,667,000	1,667,000	2,092,000
Derivative assets	40,000	40,000	76,000
Intangible assets	330,000	330,000	362,000
Goodwill	46,000	46,000	46,000
Other assets	83,000	83,000	68,000
Total assets	10,061,000	10,061,000	12,303,000
Liabilities:
Unearned premiums	385,000	385,000	395,000
Loss and loss expense reserves	1,019,000	1,019,000	1,570,000
Ceded premiums payable	44,000	44,000	33,000
Long-term debt	2,189,000	2,189,000	2,230,000
Accrued interest payable	559,000	559,000	576,000
Derivative Liability	61,000	61,000	95,000
Other liabilities	124,000	124,000	133,000
Total liabilities	9,198,000	9,198,000	11,187,000
Redeemable Noncontrolling Interest, Equity, Carrying Amount	18,000	18,000	18,000
Liabilities	9,198,000	9,198,000	11,187,000
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	267,000	267,000	257,000
Accumulated other comprehensive income	(196,000)	(196,000)	58,000
Retained earnings	728,000	728,000	726,000
Treasury stock, shares at cost: 0 and 8,202	(16,000)	(16,000)	(3,000)
Total Ambac Financial Group, Inc. stockholders’ equity	784,000	784,000	1,038,000
Noncontrolling interest	62,000	62,000	60,000
Total stockholders’ equity	846,000	846,000	1,098,000
Total liabilities and stockholders’ equity	10,061,000	10,061,000	12,303,000
Available-for-sale Securities, Amortized Cost Basis	1,979,000	1,979,000	2,140,000
Debt Securities, Available-for-sale, Allowance for Credit Loss	0	0	0
Debt Securities, Available-for-sale, Amortized Cost	1,979,000	1,979,000
Xchange
Liabilities:
Redeemable Noncontrolling Interest, Equity, Redemption Value	18,000	18,000
Redeemable Noncontrolling Interest, Equity, Carrying Amount			18,000
Short-term Investments [Member]
Assets:
Fixed maturity securities, at fair value	452,000	452,000	414,000
Stockholders’ equity:
Available-for-sale Securities, Amortized Cost Basis	452,000	452,000	415,000
Debt Securities, Available-for-sale, Allowance for Credit Loss	0	0	0
Variable Interest Entity, Primary Beneficiary [Member]
Assets:
Fixed maturity securities, at fair value	2,642,000	2,642,000	3,455,000
Restricted Cash	2,000	2,000	2,000
Derivative assets	51,000	51,000	38,000
Other assets	2,000	2,000	2,000
Total assets	4,841,000	4,841,000	6,216,000
Liabilities:
Long-term debt	3,340,000	3,340,000	4,216,000
Derivative Liability	1,476,000	1,476,000	1,940,000
Total liabilities	4,816,000	4,816,000	6,156,000
Liabilities	4,816,000	4,816,000	6,156,000
Stockholders’ equity:
Financing Receivable, after Allowance for Credit Loss	2,144,000	2,144,000	2,718,000
Gross Investment Income, Operating	(1,000)
Fixed Income Securities [Member]
Assets:
Fixed maturity securities, at fair value	1,410,000	1,410,000	1,730,000
Stockholders’ equity:
Available-for-sale Securities, Amortized Cost Basis	1,442,000	1,442,000	1,605,000
Available-for-sale Securities	1,410,000	1,410,000	1,730,000
Debt Securities, Available-for-sale, Allowance for Credit Loss	0	0	0
Short-term Investments [Member]
Stockholders’ equity:
Available-for-sale Securities	452,000	452,000	414,000
Gross Investment Income, Operating	1,000	1,000
Other Investments [Member]
Stockholders’ equity:
Available-for-sale Securities	598,000	598,000	690,000
Gross Investment Income, Operating	(23,000)	(23,000)
Fixed Income Securities, Trading
Stockholders’ equity:
Available-for-sale Securities, Amortized Cost Basis	2,000	2,000	0
Available-for-sale Securities	2,000	2,000
Gross Investment Income, Operating	(11,000)	(21,000)
Collateral Pledged [Member] | Fixed Income Securities [Member]
Assets:
Fixed maturity securities, at fair value	85,000	85,000	120,000
Stockholders’ equity:
Debt Securities, Available-for-sale, Amortized Cost	15,000	15,000	15,000
Collateral Pledged [Member] | Fixed Income Securities [Member] | Short-term Investments [Member]
Assets:
Fixed maturity securities, at fair value	70,000	70,000	105,000
Stockholders’ equity:
Available-for-sale Securities, Amortized Cost Basis	70,000	70,000	105,000
Debt Securities, Available-for-sale, Allowance for Credit Loss	0	0	0
Collateral Pledged [Member] | Short-term Investments
Stockholders’ equity:
Available-for-sale Securities, Amortized Cost Basis	70,000	70,000	105,000
Collateralized Securities | Fixed Income Securities [Member]
Stockholders’ equity:
Available-for-sale Securities	15,000	15,000	15,000
Collateralized Securities | Short-term Investments [Member]
Stockholders’ equity:
Available-for-sale Securities	$ 70,000	$ 70,000	$ 105,000