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Investments - Additional Information (Detail) (USD $) In Thousands, unless otherwise specified |  |  | 2 Months Ended | 1 Months Ended | 4 Months Ended | 6 Months Ended |  |  |  | 3 Months Ended
--- | --- | --- | --- | --- | --- | --- | --- | --- | --- | ---
Jun. 30, 2013 | Dec. 31, 2012 | Jun. 30, 2013 Successor Ambac [Member] | Apr. 30, 2013 Predecessor Ambac [Member] | Apr. 30, 2013 Predecessor Ambac [Member] | Jun. 30, 2012 Predecessor Ambac [Member] | Dec. 31, 2012 Predecessor Ambac [Member] | Jun. 30, 2013 Residential Mortgage-Backed Securities [Member] | Jun. 30, 2013 Alt-A Residential Mortgage Backed Securities [Member] Security | Jun. 30, 2013 Other asset-backed securities [Member] | Jun. 30, 2013 Asset Backed, Military Housing, Fixed Rate Securities [Member] Security | Jun. 30, 2013 Below investment grade securities and non-rated securities [Member] | Dec. 31, 2012 Below investment grade securities and non-rated securities [Member] | Mar. 31, 2013 National Century Financial Enterprises, Inc. [Member]
Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Fair value of below investment grade securities and non-rated securities |  |  |  |  |  |  |  |  |  |  |  | $ 902,845 | $ 192,190 |
Gross unrealized loss |  |  |  |  |  |  |  |  |  |  |  | 36,195 | 43,934 |
Unrealized losses on securities |  |  | 137,749 |  |  |  | 7,551 | 23,426 | 14,555 | 23,570 | 23,141 |  |  |
Number of securities in unrealized loss position |  |  |  |  |  |  |  |  | 24 |  | 6 |  |  |
Investment realized losses |  |  | 18,472 |  | 53,305 | 67,459 |  |  |  |  |  |  |  | 150,201
Investment in asset backed notes |  |  |  |  |  |  |  |  |  |  |  |  |  | 174,500
Cash recoveries |  |  |  |  |  |  |  |  |  |  |  |  |  | 39,978
Securities fair value | 6,855 | 6,945 |  |  |  |  |  |  |  |  |  |  |  |
Fair value of securities held by bankruptcy remote trust | 235,850 | 201,329 |  |  |  |  |  |  |  |  |  |  |  |
Other investments |  |  | $ (3,015) | $ 912 | $ 369 |  |  |  |  |  |  |  |  |

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- Definition Available For Sale Securities In Unrealized Loss Positions Qualitative Disclosure Number Of Positions Less Than 12 Months + References No definition available. + Details
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- Definition Aggregate losses of below investment grade securities and non rated securities in a continuous unrealized loss position. + References No definition available. + Details
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- Definition Fair value of below investment grade securities and non rated securities in a continuous unrealized loss position. + References No definition available. + Details
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- Definition Fair value of securities deposited with governmental authorities. + References No definition available. + Details
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- Details
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- Definition Other Investments Income + References No definition available. + Details
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- Definition Fair Value of securities held to collateralize and fund repayment of debt issued through a resecuritization transaction. + References No definition available. + Details
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- Definition Investments in notes or bonds that are collateralized by a specific group of underlying assets owned by the issuer of the notes or bonds which are short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. Generally, only investments with original maturities of three months or less qualify under that definition. Original maturity means original maturity to the entity holding the investment. For example, both a three-month US Treasury bill and a three-year Treasury note purchased three months from maturity qualify as cash equivalents. However, a Treasury note purchased three-years ago does not become a cash equivalent when its remaining maturity is three months. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Cash Equivalents -URI http://asc.fasb.org/extlink&oid=6507016 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 8, 9 -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. + Details
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- Definition Amount of the excess of amortized cost basis over fair value of securities that have been in a loss position for less than twelve months for securities categorized neither as held-to-maturity nor trading securities. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 6 -Subparagraph (a)(2) -URI http://asc.fasb.org/extlink&oid=6872113&loc=d3e27290-111563 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 7 -URI http://asc.fasb.org/extlink&oid=6872113&loc=d3e27337-111563 + Details
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- Definition This element represents the gross amount awarded, to be received by, or to be remitted to the entity in settlement of litigation occurring during the period. + References No definition available. + Details
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- Definition The net realized gains or losses on investments during the period, not including gains or losses on securities separately or otherwise categorized as trading, available-for-sale, or held-to-maturity. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 225 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-04.3(a)) -URI http://asc.fasb.org/extlink&oid=6879464&loc=d3e573970-122913 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 325 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6485959&loc=d3e22529-158502 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 04 -Paragraph 3 -Subparagraph a -Article 7 + Details
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