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Investments - Summary of Fair Value, Including Financial Guarantee, and Weighted-Average Underlying Rating, Excluding Financial Guarantee, of Insured Securities (Detail) - Successor [Member] - USD ($) $ in Thousands | Sep. 30, 2015 | Dec. 31, 2014
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Standard & Poor's, CCC- Rating [Member] | Ambac Assurance Corporation [Member] |  |
Investment [Line Items] |  |
Fair value of securities that include benefit of guarantees provided by financial guarantors | $ 2,172,102 | $ 2,199,719
Standard & Poor's, A Rating [Member] | Assured Guaranty Municipal Corporation [Member] |  |
Investment [Line Items] |  |
Fair value of securities that include benefit of guarantees provided by financial guarantors |  | 119,492
Standard & Poor's, A- Rating [Member] | National Public Finance Guarantee Corporation [Member] |  |
Investment [Line Items] |  |
Fair value of securities that include benefit of guarantees provided by financial guarantors | 48,695 | 67,895
Standard & Poor's, A+ Rating [Member] | Assured Guaranty Municipal Corporation [Member] |  |
Investment [Line Items] |  |
Fair value of securities that include benefit of guarantees provided by financial guarantors | 58,794 |
Standard & Poor's, A+ Rating [Member] | MBIA Insurance Corporation [Member] |  |
Investment [Line Items] |  |
Fair value of securities that include benefit of guarantees provided by financial guarantors | 29,108 | 32,460
Standard & Poor's, CCC Rating [Member] |  |
Investment [Line Items] |  |
Fair value of securities that include benefit of guarantees provided by financial guarantors | 2,308,699 | 2,419,566
Municipal Bonds [Member] | Standard & Poor's, CCC- Rating [Member] | Ambac Assurance Corporation [Member] |  |
Investment [Line Items] |  |
Fair value of securities that include benefit of guarantees provided by financial guarantors | 53,097 | 53,164
Municipal Bonds [Member] | Standard & Poor's, A Rating [Member] | Assured Guaranty Municipal Corporation [Member] |  |
Investment [Line Items] |  |
Fair value of securities that include benefit of guarantees provided by financial guarantors |  | 119,492
Municipal Bonds [Member] | Standard & Poor's, A- Rating [Member] | National Public Finance Guarantee Corporation [Member] |  |
Investment [Line Items] |  |
Fair value of securities that include benefit of guarantees provided by financial guarantors | 48,695 | 67,895
Municipal Bonds [Member] | Standard & Poor's, A+ Rating [Member] | Assured Guaranty Municipal Corporation [Member] |  |
Investment [Line Items] |  |
Fair value of securities that include benefit of guarantees provided by financial guarantors | 58,794 |
Municipal Bonds [Member] | Standard & Poor's, CCC Rating [Member] |  |
Investment [Line Items] |  |
Fair value of securities that include benefit of guarantees provided by financial guarantors | 160,586 | 240,551
Corporate Debt Securities [Member] | Standard & Poor's, A Rating [Member] | Assured Guaranty Municipal Corporation [Member] |  |
Investment [Line Items] |  |
Fair value of securities that include benefit of guarantees provided by financial guarantors |  | 0
Corporate Debt Securities [Member] | Standard & Poor's, A- Rating [Member] | National Public Finance Guarantee Corporation [Member] |  |
Investment [Line Items] |  |
Fair value of securities that include benefit of guarantees provided by financial guarantors | 0 | 0
Corporate Debt Securities [Member] | Standard & Poor's, A+ Rating [Member] | Assured Guaranty Municipal Corporation [Member] |  |
Investment [Line Items] |  |
Fair value of securities that include benefit of guarantees provided by financial guarantors | 0 |
Corporate Debt Securities [Member] | Standard & Poor's, A+ Rating [Member] | MBIA Insurance Corporation [Member] |  |
Investment [Line Items] |  |
Fair value of securities that include benefit of guarantees provided by financial guarantors | 29,108 | 32,460
Corporate Debt Securities [Member] | Standard & Poor's, CCC Rating [Member] |  |
Investment [Line Items] |  |
Fair value of securities that include benefit of guarantees provided by financial guarantors | 29,108 | 32,460
Mortgage and Asset-Backed Securities [Member] | Standard & Poor's, CCC- Rating [Member] | Ambac Assurance Corporation [Member] |  |
Investment [Line Items] |  |
Fair value of securities that include benefit of guarantees provided by financial guarantors | 2,119,005 | 2,146,555
Mortgage and Asset-Backed Securities [Member] | Standard & Poor's, CCC Rating [Member] |  |
Investment [Line Items] |  |
Fair value of securities that include benefit of guarantees provided by financial guarantors | $ 2,119,005 | $ 2,146,555

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