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Investments - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Investment [Line Items]
Payment of permitted policy claim (percent)					25.00%
Future payment of permitted policy claim (percent)					45.00%
Securities fair value	$ 6,831		$ 6,831		$ 6,790
Fair Value of Securities Placed in Trust	403,106		403,106
Successor [Member]
Investment [Line Items]
Unrealized losses on securities	58,351		58,351		20,081
Other investments	(1,424)	$ 700	10,702	$ 5,905
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments	71,181		71,181		32,269
Below Investment Grade Securities and Non-Rated Securities [Member] | Successor [Member]
Investment [Line Items]
Fair value of below investment grade securities and non-rated securities	788,174		788,174		473,656
Gross unrealized loss	44,497		44,497		16,001
Ambac Wrapped Securities [Member]
Investment [Line Items]
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments	40,877		40,877
Gains (losses) on securities held as of reporting date [Member] | Successor [Member]
Investment [Line Items]
Other investments	(3,482)	$ 329	(41)	$ 5,965
Ambac UK [Member]
Investment [Line Items]
Asset Backed Securities Fair Value Disclosure	78,925		$ 78,925		51,395
National Century Financial Enterprises, Inc. [Member]
Investment [Line Items]
Cash recoveries	$ 0				$ 35

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Asset-backed securities guaranteed by Ambac UK.

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Aggregate losses of below investment grade securities and non rated securities in a continuous unrealized loss position.

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Fair value of below investment grade securities and non rated securities in a continuous unrealized loss position.

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- Definition

Percentage of the Segregated Account of Ambac Assurance's permitted policy claims that are to be paid in cash from July 2014 forward as approved by the Rehabilitation Court.

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Fair Value of Securities Placed in Trust

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Other Investments Income

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Percentage of the Segregated Account of Ambac Assurance's permitted policy claims that were paid in cash from September 2012 through June 2014.

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Line items represent reporting concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef



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-Article 12



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Amount before tax of unrealized loss in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

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-Publisher FASB



-Name Accounting Standards Codification



-Topic 320



-SubTopic 10



-Section 50



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Amount of accumulated unrealized loss on investments in debt and equity securities classified as available-for-sale that have been in a continuous loss position for less than twelve months.

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