Fair Value Measurements - Summary of Carrying Amount and Fair Value of Ambac's Financial Assets and Liabilities (Detail) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Financial assets:
Other investments	$ 391,075	$ 285,261
Other assets	7,729	8,696
Financial liabilities:
Derivative liabilities	16,700	34,543
Successor [Member]
Financial assets:
Fixed income securities	6,186,101	5,334,120
Short term investments	130,732	225,789
Successor [Member] \| Total Fair Value [Member]
Financial assets:
Other investments	403,414	298,095
Cash	21,218	35,744
Loans	4,467	5,128
Total financial assets	21,105,906	20,051,480
Financial liabilities:
Obligations under investment and repurchase agreements	82,541	101,400
Liabilities for net financial guarantees written	4,175,019	2,325,859
Long-term debt	1,422,602	1,235,721
Total financial liabilities	20,350,795	18,272,701
Successor [Member] \| Total Fair Value [Member] \| Variable Interest Entity [Member]
Financial assets:
Restricted cash	5,477	5,822
Loans		11,690,324
Financial liabilities:
Long-term debt	11,930,434	12,327,960
Successor [Member] \| Carrying Amount [Member]
Financial assets:
Other investments	419,885	310,600
Cash	21,218	35,744
Loans	4,513	5,206
Total financial assets	21,122,423	20,064,063
Financial liabilities:
Obligations under investment and repurchase agreements	82,358	100,358
Liabilities for net financial guarantees written	2,787,131	2,033,484
Long-term debt	1,510,529	1,481,045
Total financial liabilities	19,050,651	18,224,608
Successor [Member] \| Carrying Amount [Member] \| Variable Interest Entity [Member]
Financial assets:
Restricted cash	5,477	5,822
Loans	11,476,766	11,690,324
Financial liabilities:
Long-term debt	11,930,434	12,327,960
Successor [Member] \| Investments Measured at NAV as a Practical Expedient [Member]
Financial assets:
Other investments	312,503	239,516
Successor [Member] \| Level 1 [Member]
Financial assets:
Other investments	78,572	45,745
Cash	21,218	35,744
Loans	0	0
Total financial assets	390,761	463,868
Financial liabilities:
Obligations under investment and repurchase agreements	0	0
Liabilities for net financial guarantees written	0	0
Long-term debt	0	0
Total financial liabilities	36	0
Successor [Member] \| Level 1 [Member] \| Variable Interest Entity [Member]
Financial assets:
Restricted cash	5,477	5,822
Loans		0
Financial liabilities:
Long-term debt	0	0
Successor [Member] \| Level 2 [Member]
Financial assets:
Other investments	0	0
Cash	0	0
Loans	0	0
Total financial assets	5,238,149	4,490,636
Financial liabilities:
Obligations under investment and repurchase agreements	0	0
Liabilities for net financial guarantees written	0	0
Long-term debt	1,121,249	132,837
Total financial liabilities	13,007,407	11,400,158
Successor [Member] \| Level 2 [Member] \| Variable Interest Entity [Member]
Financial assets:
Restricted cash	0	0
Loans		0
Financial liabilities:
Long-term debt	9,347,134	9,147,790
Successor [Member] \| Level 3 [Member]
Financial assets:
Other investments	12,339	12,834
Cash	0	0
Loans	4,467	5,128
Total financial assets	15,164,493	14,857,460
Financial liabilities:
Obligations under investment and repurchase agreements	82,541	101,400
Liabilities for net financial guarantees written	4,175,019	2,325,859
Long-term debt	301,353	1,102,884
Total financial liabilities	7,343,352	6,872,543
Successor [Member] \| Level 3 [Member] \| Variable Interest Entity [Member]
Financial assets:
Restricted cash	0	0
Loans		11,690,324
Financial liabilities:
Long-term debt	2,583,300	3,180,170
Successor [Member] \| Interest Rate Swaps [Member] \| Total Fair Value [Member]
Financial assets:
Derivative assets	103,373	84,886
Successor [Member] \| Interest Rate Swaps [Member] \| Carrying Amount [Member]
Financial assets:
Derivative assets	103,373	84,886
Successor [Member] \| Interest Rate Swaps [Member] \| Level 1 [Member]
Financial assets:
Derivative assets	0	0
Successor [Member] \| Interest Rate Swaps [Member] \| Level 2 [Member]
Financial assets:
Derivative assets	21,340	21,848
Successor [Member] \| Interest Rate Swaps [Member] \| Level 3 [Member]
Financial assets:
Derivative assets	82,033	63,038
Successor [Member] \| Municipal Bonds [Member] \| Total Fair Value [Member]
Financial assets:
Fixed income securities	399,522	420,770
Successor [Member] \| Municipal Bonds [Member] \| Carrying Amount [Member]
Financial assets:
Fixed income securities	399,522	420,770
Successor [Member] \| Municipal Bonds [Member] \| Level 1 [Member]
Financial assets:
Fixed income securities	0	0
Successor [Member] \| Municipal Bonds [Member] \| Level 2 [Member]
Financial assets:
Fixed income securities	399,522	420,770
Successor [Member] \| Municipal Bonds [Member] \| Level 3 [Member]
Financial assets:
Fixed income securities	0	0
Successor [Member] \| Corporate Obligations [Member] \| Total Fair Value [Member]
Financial assets:
Fixed income securities	1,872,756	1,593,669
Successor [Member] \| Corporate Obligations [Member] \| Total Fair Value [Member] \| Variable Interest Entity [Member]
Financial assets:
Fixed income securities	2,828,685	2,588,556
Successor [Member] \| Corporate Obligations [Member] \| Carrying Amount [Member]
Financial assets:
Fixed income securities	1,872,756	1,593,669
Successor [Member] \| Corporate Obligations [Member] \| Carrying Amount [Member] \| Variable Interest Entity [Member]
Financial assets:
Fixed income securities	2,828,685	2,588,556
Successor [Member] \| Corporate Obligations [Member] \| Level 1 [Member]
Financial assets:
Fixed income securities	0	0
Successor [Member] \| Corporate Obligations [Member] \| Level 1 [Member] \| Variable Interest Entity [Member]
Financial assets:
Fixed income securities	0	0
Successor [Member] \| Corporate Obligations [Member] \| Level 2 [Member]
Financial assets:
Fixed income securities	1,872,756	1,593,669
Successor [Member] \| Corporate Obligations [Member] \| Level 2 [Member] \| Variable Interest Entity [Member]
Financial assets:
Fixed income securities	0	0
Successor [Member] \| Corporate Obligations [Member] \| Level 3 [Member]
Financial assets:
Fixed income securities	0	0
Successor [Member] \| Corporate Obligations [Member] \| Level 3 [Member] \| Variable Interest Entity [Member]
Financial assets:
Fixed income securities	2,828,685	2,588,556
Successor [Member] \| Foreign Obligations [Member] \| Total Fair Value [Member]
Financial assets:
Fixed income securities	56,923	96,306
Successor [Member] \| Foreign Obligations [Member] \| Carrying Amount [Member]
Financial assets:
Fixed income securities	56,923	96,306
Successor [Member] \| Foreign Obligations [Member] \| Level 1 [Member]
Financial assets:
Fixed income securities	56,365	87,808
Successor [Member] \| Foreign Obligations [Member] \| Level 2 [Member]
Financial assets:
Fixed income securities	558	8,498
Successor [Member] \| Foreign Obligations [Member] \| Level 3 [Member]
Financial assets:
Fixed income securities	0	0
Successor [Member] \| US Government Debt Securities [Member] \| Total Fair Value [Member]
Financial assets:
Fixed income securities	33,425	26,687
Fixed income securities, pledged as collateral	64,972	64,555
Successor [Member] \| US Government Debt Securities [Member] \| Carrying Amount [Member]
Financial assets:
Fixed income securities	33,425	26,687
Fixed income securities, pledged as collateral	64,972	64,555
Successor [Member] \| US Government Debt Securities [Member] \| Level 1 [Member]
Financial assets:
Fixed income securities	33,425	26,687
Fixed income securities, pledged as collateral	64,972	64,555
Successor [Member] \| US Government Debt Securities [Member] \| Level 2 [Member]
Financial assets:
Fixed income securities	0	0
Fixed income securities, pledged as collateral	0	0
Successor [Member] \| US Government Debt Securities [Member] \| Level 3 [Member]
Financial assets:
Fixed income securities	0	0
Fixed income securities, pledged as collateral	0	0
Successor [Member] \| U.S. Agency Obligations [Member] \| Total Fair Value [Member]
Financial assets:
Fixed income securities	4,106	4,212
Successor [Member] \| U.S. Agency Obligations [Member] \| Carrying Amount [Member]
Financial assets:
Fixed income securities	4,106	4,212
Successor [Member] \| U.S. Agency Obligations [Member] \| Level 1 [Member]
Financial assets:
Fixed income securities	0	0
Successor [Member] \| U.S. Agency Obligations [Member] \| Level 2 [Member]
Financial assets:
Fixed income securities	4,106	4,212
Successor [Member] \| U.S. Agency Obligations [Member] \| Level 3 [Member]
Financial assets:
Fixed income securities	0	0
Successor [Member] \| Residential Mortgage-Backed Securities [Member] \| Total Fair Value [Member]
Financial assets:
Fixed income securities	2,387,531	1,977,338
Successor [Member] \| Residential Mortgage-Backed Securities [Member] \| Carrying Amount [Member]
Financial assets:
Fixed income securities	2,387,531	1,977,338
Successor [Member] \| Residential Mortgage-Backed Securities [Member] \| Level 1 [Member]
Financial assets:
Fixed income securities	0	0
Successor [Member] \| Residential Mortgage-Backed Securities [Member] \| Level 2 [Member]
Financial assets:
Fixed income securities	1,707,956	1,488,454
Successor [Member] \| Residential Mortgage-Backed Securities [Member] \| Level 3 [Member]
Financial assets:
Fixed income securities	679,575	488,884
Successor [Member] \| Collateralized Debt Obligations [Member] \| Total Fair Value [Member]
Financial assets:
Fixed income securities	106,844	84,267
Successor [Member] \| Collateralized Debt Obligations [Member] \| Carrying Amount [Member]
Financial assets:
Fixed income securities	106,844	84,267
Successor [Member] \| Collateralized Debt Obligations [Member] \| Level 1 [Member]
Financial assets:
Fixed income securities	0	0
Successor [Member] \| Collateralized Debt Obligations [Member] \| Level 2 [Member]
Financial assets:
Fixed income securities	106,844	84,267
Successor [Member] \| Collateralized Debt Obligations [Member] \| Level 3 [Member]
Financial assets:
Fixed income securities	0	0
Successor [Member] \| Asset-backed Securities [Member] \| Total Fair Value [Member]
Financial assets:
Fixed income securities	1,129,290	840,527
Successor [Member] \| Asset-backed Securities [Member] \| Carrying Amount [Member]
Financial assets:
Fixed income securities	1,129,290	840,527
Successor [Member] \| Asset-backed Securities [Member] \| Level 1 [Member]
Financial assets:
Fixed income securities	0	0
Successor [Member] \| Asset-backed Securities [Member] \| Level 2 [Member]
Financial assets:
Fixed income securities	1,056,391	840,527
Successor [Member] \| Asset-backed Securities [Member] \| Level 3 [Member]
Financial assets:
Fixed income securities	72,899	0
Successor [Member] \| Short-Term [Member] \| Total Fair Value [Member]
Financial assets:
Short term investments	130,732	225,789
Successor [Member] \| Short-Term [Member] \| Carrying Amount [Member]
Financial assets:
Short term investments	130,732	225,789
Successor [Member] \| Short-Term [Member] \| Level 1 [Member]
Financial assets:
Short term investments	130,732	197,398
Successor [Member] \| Short-Term [Member] \| Level 2 [Member]
Financial assets:
Short term investments	0	28,391
Successor [Member] \| Short-Term [Member] \| Level 3 [Member]
Financial assets:
Short term investments	0	0
Successor [Member] \| Other Assets [Member] \| Total Fair Value [Member]
Financial assets:
Other assets	7,729	8,696
Successor [Member] \| Other Assets [Member] \| Carrying Amount [Member]
Financial assets:
Other assets	7,729	8,696
Successor [Member] \| Other Assets [Member] \| Level 1 [Member]
Financial assets:
Other assets	0	0
Successor [Member] \| Other Assets [Member] \| Level 2 [Member]
Financial assets:
Other assets	0	0
Successor [Member] \| Other Assets [Member] \| Level 3 [Member]
Financial assets:
Other assets	7,729	8,696
Successor [Member] \| Futures Contracts [Member] \| Total Fair Value [Member]
Financial assets:
Derivative assets		109
Successor [Member] \| Futures Contracts [Member] \| Carrying Amount [Member]
Financial assets:
Derivative assets		109
Successor [Member] \| Futures Contracts [Member] \| Level 1 [Member]
Financial assets:
Derivative assets		109
Successor [Member] \| Futures Contracts [Member] \| Level 2 [Member]
Financial assets:
Derivative assets		0
Successor [Member] \| Futures Contracts [Member] \| Level 3 [Member]
Financial assets:
Derivative assets		0
Futures Contracts [Member] \| Successor [Member] \| Total Fair Value [Member]
Financial liabilities:
Derivative liabilities	36	0
Futures Contracts [Member] \| Successor [Member] \| Carrying Amount [Member]
Financial liabilities:
Derivative liabilities	36	0
Futures Contracts [Member] \| Successor [Member] \| Level 1 [Member]
Financial liabilities:
Derivative liabilities	36	0
Futures Contracts [Member] \| Successor [Member] \| Level 2 [Member]
Financial liabilities:
Derivative liabilities	0	0
Futures Contracts [Member] \| Successor [Member] \| Level 3 [Member]
Financial liabilities:
Derivative liabilities	0	0
Interest Rate Swaps [Member] \| Successor [Member] \| Total Fair Value [Member]
Financial liabilities:
Derivative liabilities - interest rate swaps - asset position	(97,964)	(52,128)
Derivative liabilities	516,638	370,943
Interest Rate Swaps [Member] \| Successor [Member] \| Total Fair Value [Member] \| Variable Interest Entity [Member]
Financial liabilities:
Derivative liabilities	2,304,789	1,965,265
Interest Rate Swaps [Member] \| Successor [Member] \| Carrying Amount [Member]
Financial liabilities:
Derivative liabilities - interest rate swaps - asset position	(97,964)	(52,128)
Derivative liabilities	516,638	370,943
Interest Rate Swaps [Member] \| Successor [Member] \| Carrying Amount [Member] \| Variable Interest Entity [Member]
Financial liabilities:
Derivative liabilities	2,304,789	1,965,265
Interest Rate Swaps [Member] \| Successor [Member] \| Level 1 [Member]
Financial liabilities:
Derivative liabilities - interest rate swaps - asset position	0	0
Derivative liabilities	0	0
Interest Rate Swaps [Member] \| Successor [Member] \| Level 1 [Member] \| Variable Interest Entity [Member]
Financial liabilities:
Derivative liabilities	0	0
Interest Rate Swaps [Member] \| Successor [Member] \| Level 2 [Member]
Financial liabilities:
Derivative liabilities - interest rate swaps - asset position	(97,964)	(52,128)
Derivative liabilities	332,199	243,256
Interest Rate Swaps [Member] \| Successor [Member] \| Level 2 [Member] \| Variable Interest Entity [Member]
Financial liabilities:
Derivative liabilities	2,304,789	1,965,265
Interest Rate Swaps [Member] \| Successor [Member] \| Level 3 [Member]
Financial liabilities:
Derivative liabilities - interest rate swaps - asset position	0	0
Derivative liabilities	184,439	127,687
Interest Rate Swaps [Member] \| Successor [Member] \| Level 3 [Member] \| Variable Interest Entity [Member]
Financial liabilities:
Derivative liabilities	0	0
Credit Derivatives [Member] \| Successor [Member] \| Total Fair Value [Member]
Financial liabilities:
Derivative liabilities	16,700	34,543
Credit Derivatives [Member] \| Successor [Member] \| Carrying Amount [Member]
Financial liabilities:
Derivative liabilities	16,700	34,543
Credit Derivatives [Member] \| Successor [Member] \| Level 1 [Member]
Financial liabilities:
Derivative liabilities	0	0
Credit Derivatives [Member] \| Successor [Member] \| Level 2 [Member]
Financial liabilities:
Derivative liabilities	0	0
Credit Derivatives [Member] \| Successor [Member] \| Level 3 [Member]
Financial liabilities:
Derivative liabilities	16,700	34,543
Currency Swaps [Member] \| Successor [Member] \| Total Fair Value [Member] \| Variable Interest Entity [Member]
Financial assets:
Derivative assets	68,676
Financial liabilities:
Derivative liabilities		(36,862)
Currency Swaps [Member] \| Successor [Member] \| Carrying Amount [Member] \| Variable Interest Entity [Member]
Financial assets:
Derivative assets	68,676
Financial liabilities:
Derivative liabilities		(36,862)
Currency Swaps [Member] \| Successor [Member] \| Level 1 [Member] \| Variable Interest Entity [Member]
Financial assets:
Derivative assets	0
Financial liabilities:
Derivative liabilities		0
Currency Swaps [Member] \| Successor [Member] \| Level 2 [Member] \| Variable Interest Entity [Member]
Financial assets:
Derivative assets	68,676
Financial liabilities:
Derivative liabilities		(36,862)
Currency Swaps [Member] \| Successor [Member] \| Level 3 [Member] \| Variable Interest Entity [Member]
Financial assets:
Derivative assets	$ 0
Financial liabilities:
Derivative liabilities		$ 0

Guaranteed investment agreements at fair value.

No definition available.

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- Definition

Fair value of restricted cash and cash equivalents.

+ References

No definition available.

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- Definition

Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

+ References

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- Definition

Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

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- Definition

Fair value portion of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.

+ References

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- Definition

Fair value, before effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes assets elected not to be offset. Excludes assets not subject to a master netting arrangement.

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Fair value, before effects of master netting arrangements, of a financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes liabilities elected not to be offset. Excludes liabilities not subject to a master netting arrangement.

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- Definition

Fair value of asset associated with financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset.

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- Definition

Fair value portion of investments accounted under the equity method.

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- Definition

Fair value portion of guarantee, including, but not limited to, financial standby letter of credit, fair value guarantee, guarantee of collection of scheduled contractual cash flows from financial assets, and contracts that contingently require the guarantor to make payments or perform services.

+ References

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