Schedule I - Summary of Investments Other Than Investments in Related Parties (Detail) (Successor Ambac [Member], USD $) In Thousands, unless otherwise specified	Dec. 31, 2013
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Amortized Cost	$ 6,565,637
Estimated Fair Value	6,523,727
Amount at which shown in the balance sheet	6,523,727
U.S. Government Obligations [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Amortized Cost	254,611
Estimated Fair Value	252,471
Amount at which shown in the balance sheet	252,471
U.S. Agency Obligations [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Amortized Cost	32,214
Estimated Fair Value	32,154
Amount at which shown in the balance sheet	32,154
Municipal Obligations [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Amortized Cost	1,405,293
Estimated Fair Value	1,377,723
Amount at which shown in the balance sheet	1,377,723
Residential Mortgage-Backed Securities [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Amortized Cost	1,516,877
Estimated Fair Value	1,558,625
Amount at which shown in the balance sheet	1,558,625
Collateralized Debt Obligations [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Amortized Cost	184,118
Estimated Fair Value	183,872
Amount at which shown in the balance sheet	183,872
Other Asset-Backed Securities [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Amortized Cost	1,020,251
Estimated Fair Value	992,448
Amount at which shown in the balance sheet	992,448
Corporate Obligations [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Amortized Cost	1,508,377
Estimated Fair Value	1,489,369
Amount at which shown in the balance sheet	1,489,369
Foreign Obligations [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Amortized Cost	131,709
Estimated Fair Value	124,877
Amount at which shown in the balance sheet	124,877
Short-Term [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Amortized Cost	271,118
Estimated Fair Value	271,119
Amount at which shown in the balance sheet	271,119
Other [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Amortized Cost	241,069
Estimated Fair Value	241,069
Amount at which shown in the balance sheet	$ 241,069

This element represents the carrying (reported) amount of the entity's investments as of the balance sheet date. This amount may represent the individual investment's or group of similar investments' original cost, fair value, or such other amount at which the investment is shown in the entity's balance sheet.

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 15

-Article 12

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 946

-SubTopic 320

-Section S99

-Paragraph 7

-Subparagraph (SX 210.12-15)

-URI http://asc.fasb.org/extlink&oid=6955306&loc=d3e611379-123010

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This item represents the original cost of the entity's investments including investments in equity securities and, as to fixed maturities, original cost reduced by repayments and adjusted for amortization of premiums or accrual of discounts.

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This item represents the reported amount of the entity's investments measured at fair value. Fair value is the price that would be received to sell an investment in an orderly transaction between market participants at the balance sheet [measurement] date.

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