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Investments - Summary of Net Investment Income (Detail) (USD $) In Thousands, unless otherwise specified | 3 Months Ended | 4 Months Ended | 5 Months Ended | 9 Months Ended
--- | --- | --- | --- | ---
Sep. 30, 2014 | Sep. 30, 2013 | Apr. 30, 2013 | Sep. 30, 2013 | Sep. 30, 2014
Successor Ambac [Member] |  |  |  |  |
Investment [Line Items] |  |  |  |  |
Fixed income securities | $ 84,339 | $ 53,301 |  | $ 83,732 | $ 233,878
Short-term investments | 832 | 626 |  | 788 | 2,000
Loans | 123 | 109 |  | 193 | 415
Investment expense | (2,413) | (2,260) |  | (3,726) | (7,723)
Securities available-for-sale and short-term | 82,881 | 51,776 |  | 80,987 | 228,570
Other investments | 700 | 350 |  | (2,665) | 5,905
Total net investment income | 83,581 | 52,126 |  | 78,322 | 234,475
Predecessor Ambac [Member] |  |  |  |  |
Investment [Line Items] |  |  |  |  |
Fixed income securities |  |  | 118,097 |  |
Short-term investments |  |  | 677 |  |
Loans |  |  | 146 |  |
Investment expense |  |  | (2,549) |  |
Securities available-for-sale and short-term |  |  | 116,371 |  |
Other investments |  |  | 369 |  |
Total net investment income |  |  | 116,740 |  |
Gains (losses) on securities held as of reporting date [Member] | Successor Ambac [Member] |  |  |  |  |
Investment [Line Items] |  |  |  |  |
Other investments | $ 329 | $ 1,577 | $ (78) | $ (784) | $ 5,965

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- Definition Amount of operating dividend and interest income, including amortization and accretion of premiums and discounts, on available-for-sale securities. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Available-for-Sale Securities -URI http://asc.fasb.org/extlink&oid=6505594 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 225 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-04.2) -URI http://asc.fasb.org/extlink&oid=6879574&loc=d3e536633-122882 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 04 -Paragraph 2 -Article 9 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 35 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=27723805&loc=d3e24721-111560 + Details
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