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Investments - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended			12 Months Ended
	Mar. 31, 2016	Sep. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Dec. 31, 2015
Investment [Line Items]
Payment of permitted policy claim (percent)				25.00%
Future payment of permitted policy claim (percent)				45.00%
Securities fair value	$ 5,939				$ 6,762
Fair Value of Securities Placed in Trust	381,249				396,100
Successor [Member]
Investment [Line Items]
Unrealized losses on securities	46,348				82,799
Other investments	2,839		$ 9,651
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments	76,831				104,206
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	1,053,711				953,000
Gross unrealized loss	63,981				69,214
Ambac Wrapped Securities [Member]
Investment [Line Items]
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments	57,269
Gains (losses) on securities held as of reporting date [Member] | Successor [Member]
Investment [Line Items]
Other investments	1,301		$ 6,255
Ambac UK [Member]
Investment [Line Items]
Asset Backed Securities Fair Value Disclosure	$ 118,968				$ 119,802
National Century Financial Enterprises, Inc. [Member]
Investment [Line Items]
Cash recoveries		$ 0		$ 35

X

- Definition

Asset-backed securities guaranteed by Ambac UK.

+ References

No definition available.

+ Details

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- Definition

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

+ References

No definition available.

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- Definition

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

+ References

No definition available.

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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.

+ References

No definition available.

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- Definition

Fair value of securities deposited with governmental authorities.

+ References

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- Definition

Fair Value of Securities Placed in Trust

+ References

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- Definition

Other Investments Income

+ References

No definition available.

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- Definition

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

+ References

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- Definition

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.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Article 12
-Section 12
-Sentence Column A

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- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27161-111563

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- Definition

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.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 6
-Subparagraph (a)(2)
-URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27290-111563

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27337-111563

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Amount of judgment or settlement awarded to (against) the entity in respect of litigation.

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