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Derivative Instruments - Summary of Notional for VIE Derivatives Outstanding (Detail) (USD $) In Thousands, unless otherwise specified | Jun. 30, 2013 | Dec. 31, 2012
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Schedule Of Notional For Variable Interest Entity Derivatives Outstanding [Line Items] |  |
Derivative products, Notional Amount | $ 232,267 | $ 213,585
Successor Ambac [Member] | Interest Rate Swaps [Member] |  |
Schedule Of Notional For Variable Interest Entity Derivatives Outstanding [Line Items] |  |
Derivative products, Notional Amount | 1,669,298 |
Successor Ambac [Member] | Interest Rate Swaps-Pay-Fixed/Receive-Variable [Member] |  |
Schedule Of Notional For Variable Interest Entity Derivatives Outstanding [Line Items] |  |
Derivative products, Notional Amount | 4,356,549 |
Successor Ambac [Member] | Currency Swaps [Member] |  |
Schedule Of Notional For Variable Interest Entity Derivatives Outstanding [Line Items] |  |
Derivative products, Notional Amount | 707,264 |
Successor Ambac [Member] | Credit Derivatives [Member] |  |
Schedule Of Notional For Variable Interest Entity Derivatives Outstanding [Line Items] |  |
Derivative products, Notional Amount | 18,958 |
Predecessor Ambac [Member] | Interest Rate Swaps [Member] |  |
Schedule Of Notional For Variable Interest Entity Derivatives Outstanding [Line Items] |  |
Derivative products, Notional Amount |  | 1,782,999
Predecessor Ambac [Member] | Interest Rate Swaps-Pay-Fixed/Receive-Variable [Member] |  |
Schedule Of Notional For Variable Interest Entity Derivatives Outstanding [Line Items] |  |
Derivative products, Notional Amount |  | 4,707,454
Predecessor Ambac [Member] | Currency Swaps [Member] |  |
Schedule Of Notional For Variable Interest Entity Derivatives Outstanding [Line Items] |  |
Derivative products, Notional Amount |  | 755,438
Predecessor Ambac [Member] | Credit Derivatives [Member] |  |
Schedule Of Notional For Variable Interest Entity Derivatives Outstanding [Line Items] |  |
Derivative products, Notional Amount |  | $ 20,885

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- Definition Aggregate notional amount specified by the derivative(s). Expressed as an absolute value. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Article 12 -Section 13 -Sentence Column B + Details
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- Definition Fair value of derivative liability, presented on a gross basis even when the derivative instrument is subject to master netting arrangements and qualifies for net presentation in the statement of financial position. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 133 -Paragraph 205G -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 133 -Paragraph 44C -Subparagraph a -Clause 1 -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4B -Subparagraph (a),(c) -URI http://asc.fasb.org/extlink&oid=7476318&loc=SL5624163-113959 + Details
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