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Fair Value Measurements - Information about Valuation Inputs for Fixed Income Securities Classified as Level 3 (Detail) | 9 Months Ended | 12 Months Ended
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Sep. 30, 2013 Successor Ambac [Member] Corporate Obligations [Member] | Sep. 30, 2013 Successor Ambac [Member] U.S. Agency Obligations [Member] | Sep. 30, 2013 Successor Ambac [Member] Other Commercial Asset-Backed [Member] | Dec. 31, 2012 Predecessor Ambac [Member] Corporate Obligations [Member] | Dec. 31, 2012 Predecessor Ambac [Member] Collateralized Debt Obligations [Member] | Dec. 31, 2012 Predecessor Ambac [Member] Other Commercial Asset-Backed [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items] |  |  |  |  |  |
Coupon rate | 0.345% | 6.98% | 0.66% | 0.345% | 1.05% | 0.71%
Maturity | 20 years 4 months 21 days | 1 year 7 months 13 days | 7 years 3 months 22 days | 21 years 1 month 21 days | 1 year 6 months 4 days | 7 years 10 months 10 days
Yield | 6.63% | 0.34% | 2.75% | 6.08% | 5.92% | 7.50%

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- Definition Fair value inputs coupon rate. + References No definition available. + Details
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- Definition Fair value inputs maturity. + References No definition available. + Details
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- Definition Fair value inputs yield. + References No definition available. + Details
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- Details
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