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Investments - Additional Information (Detail) - USD ($) $ in Thousands | 3 Months Ended | 6 Months Ended |
--- | --- | --- | ---
Jun. 30, 2017 | Jun. 30, 2016 | Mar. 31, 2016 | Jun. 30, 2017 | Jun. 30, 2016 | Dec. 31, 2016
Investment [Line Items] |  |  |  |  |  |
Securities fair value | $ 6,021 |  |  | $ 6,021 |  | $ 5,872
Fair Value of Securities Placed in Trust | 352,446 |  |  | 352,446 |  | 360,759
Successor [Member] |  |  |  |  |  |
Investment [Line Items] |  |  |  |  |  |
Other investments | 452,032 |  |  | 452,032 |  | 450,307
Unrealized losses on securities | 21,985 |  |  | 21,985 |  | 29,944
Cash recoveries |  |  | $ 995,000 |  |  |
Other investments | 4,217 | $ 6,390 |  | 12,626 | $ 9,229 |
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments | 62,108 |  |  | 62,108 |  | 79,642
Below Investment Grade Securities and Non-Rated Securities [Member] | Successor [Member] |  |  |  |  |  |
Investment [Line Items] |  |  |  |  |  |
Fair value of below investment grade securities and non-rated securities | 997,251 |  |  | 997,251 |  | 890,952
Gross unrealized loss | 49,242 |  |  | 49,242 |  | 53,273
Ambac Wrapped Securities [Member] |  |  |  |  |  |
Investment [Line Items] |  |  |  |  |  |
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments | 32,184 |  |  | 32,184 |  |
Gains (losses) on securities held as of reporting date [Member] | Successor [Member] |  |  |  |  |  |
Investment [Line Items] |  |  |  |  |  |
Other investments | 930 | $ 3,742 |  | 6,513 | $ 5,417 |
Ambac UK [Member] |  |  |  |  |  |
Investment [Line Items] |  |  |  |  |  |
Asset Backed Securities Fair Value Disclosure | 169,672 |  |  | 169,672 |  | 118,813
Interest Rate Contract [Member] | Successor [Member] |  |  |  |  |  |
Investment [Line Items] |  |  |  |  |  |
Other investments | 223,364 |  |  | 223,364 |  | 261,315
Reported Value Measurement [Member] | Interest Rate Contract [Member] | Successor [Member] |  |  |  |  |  |
Investment [Line Items] |  |  |  |  |  |
Other investments | $ 52,264 |  |  | $ 52,264 |  | $ 51,158

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