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Long-Term Debt - Carrying Value of Long-Term Debt (Parenthetical) (Detail) | 12 Months Ended
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Dec. 31, 2012 | Dec. 31, 2011
Debt Instrument [Line Items] |  |
Percentage of debt instrument | 6.65% |
Ambac Assurance Corporation [Member] | 5.1% surplus notes, general account, due 2020 [Member] |  |
Debt Instrument [Line Items] |  |
Percentage of debt instrument | 5.10% | 5.10%
Debt instrument due | 2020 | 2020
Ambac Assurance Corporation [Member] | 5.1% surplus notes, segregated account, due 2020 [Member] |  |
Debt Instrument [Line Items] |  |
Percentage of debt instrument | 5.10% | 5.10%
Debt instrument due | 2020 | 2020
Ambac Assurance Corporation [Member] | 5.1% junior surplus notes, segregated account, due 2020 [Member] |  |
Debt Instrument [Line Items] |  |
Percentage of debt instrument | 5.10% | 5.10%
Debt instrument due | 2020 | 2020

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- Definition Debt Instruments Maturity Year + References No definition available. + Details
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- Definition Interest rate stated in the contractual debt agreement. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 22 -Article 5 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.22(a)(1)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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- Details
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