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Investments - Additional Information (Detail) - USD ($) $ in Thousands | 4 Months Ended | 8 Months Ended | 12 Months Ended
--- | --- | --- | ---
Apr. 30, 2013 | Dec. 31, 2013 | Dec. 31, 2015 | Dec. 31, 2014
Investment [Line Items] |  |  |  |
Payment of permitted policy claim (percent) |  |  |  | 25.00%
Future payment of permitted policy claim (percent) |  |  |  | 45.00%
Securities fair value |  |  | $ 6,762 | $ 6,790
Fair value of securities held by bankruptcy remote trust |  |  | 396,100 | 0
Successor [Member] |  |  |  |
Investment [Line Items] |  |  |  |
Unrealized losses on securities |  |  | 82,799 | 20,081
Other investments |  | $ 3,580 | 16,952 | 8,108
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments |  |  | 104,206 | 32,269
Predecessor [Member] |  |  |  |
Investment [Line Items] |  |  |  |
Other investments | $ 369 |  |  |
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 |  |  | 953,000 | 473,656
Gross unrealized loss |  |  | 69,214 | 16,001
Ambac Wrapped Securities [Member] | Successor [Member] |  |  |  |
Investment [Line Items] |  |  |  |
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments |  |  | 63,127 |
Gains (losses) on securities held as of reporting date [Member] | Successor [Member] |  |  |  |
Investment [Line Items] |  |  |  |
Other investments |  | 1,878 | 7,649 | 7,200
Gains (losses) on securities held as of reporting date [Member] | Predecessor [Member] |  |  |  |
Investment [Line Items] |  |  |  |
Other investments | 369 |  |  |
National Century Financial Enterprises, Inc. [Member] |  |  |  |
Investment [Line Items] |  |  |  |
Cash recoveries | $ 39,978 | $ 1,441 | 96 | 35
Fixed Income Securities [Member] | Successor [Member] |  |  |  |
Investment [Line Items] |  |  |  |
Unrealized losses on securities |  |  | 82,741 | 19,966
Fixed Income Securities [Member] | Residential Mortgage-Backed Securities [Member] | Successor [Member] |  |  |  |
Investment [Line Items] |  |  |  |
Unrealized losses on securities |  |  | 53,367 | 12,391
Fixed Income Securities [Member] | Asset-backed Securities [Member] | Successor [Member] |  |  |  |
Investment [Line Items] |  |  |  |
Unrealized losses on securities |  |  | $ 3,456 | $ 155

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