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Fair Value Measurements - Summary of Information about Described Model Inputs Used to Determine Fair Value of Each Class of Credit Derivatives (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified | Jun. 30, 2013 | Dec. 31, 2012
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Schedule Of Information About Described Model Inputs Used To Determine Fair Value Of Each Class Of Credit Derivative [Line Items] |  |
Notional outstanding | $ 5,861,060 | $ 11,281,777
Successor Ambac [Member] |  |
Schedule Of Information About Described Model Inputs Used To Determine Fair Value Of Each Class Of Credit Derivative [Line Items] |  |
Notional outstanding | 5,861,060 |
Predecessor Ambac [Member] |  |
Schedule Of Information About Described Model Inputs Used To Determine Fair Value Of Each Class Of Credit Derivative [Line Items] |  |
Notional outstanding |  | 11,281,777
CLO [Member] | Successor Ambac [Member] |  |
Schedule Of Information About Described Model Inputs Used To Determine Fair Value Of Each Class Of Credit Derivative [Line Items] |  |
Notional outstanding | 1,750,217 |
Weighted average reference obligation price | $ 97.7 |
Weighted average life (WAL) in years | 2 years 6 months |
Weighted average credit rating | AA |
Weighted average relative change ratio | 35.30% |
CVA percentage | 15.10% |
Fair value of derivative liabilities | (11,996) |
CLO [Member] | Predecessor Ambac [Member] |  |
Schedule Of Information About Described Model Inputs Used To Determine Fair Value Of Each Class Of Credit Derivative [Line Items] |  |
Notional outstanding |  | 6,155,767
Weighted average reference obligation price |  | $ 96.5
Weighted average life (WAL) in years |  | 2 years 2 months 12 days
Weighted average credit rating |  | AA-
Weighted average relative change ratio |  | 34.40%
CVA percentage |  | 55.00%
Fair value of derivative liabilities |  | (34,645)
Other [Member] | Successor Ambac [Member] |  |
Schedule Of Information About Described Model Inputs Used To Determine Fair Value Of Each Class Of Credit Derivative [Line Items] |  |
Notional outstanding | 2,940,586 |
Weighted average reference obligation price | $ 88.5 |
Weighted average life (WAL) in years | 4 years 3 months 18 days |
Weighted average credit rating | A- |
Weighted average relative change ratio | 37.40% |
CVA percentage | 31.20% |
Fair value of derivative liabilities | (134,161) |
Other [Member] | Predecessor Ambac [Member] |  |
Schedule Of Information About Described Model Inputs Used To Determine Fair Value Of Each Class Of Credit Derivative [Line Items] |  |
Notional outstanding |  | 3,701,387
Weighted average reference obligation price |  | $ 86.9
Weighted average life (WAL) in years |  | 4 years 2 months 12 days
Weighted average credit rating |  | A
Weighted average relative change ratio |  | 38.20%
CVA percentage |  | 55.00%
Fair value of derivative liabilities |  | $ (116,086)

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- Definition Fair value input weighted average credit rating. + References No definition available. + Details
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- Definition Fair value input weighted average life. + References No definition available. + Details
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- Definition Fair value input weighted average obligation price. + References No definition available. + Details
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- Definition Fair value input weighted average relative change ratio. + References No definition available. + Details
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- Definition Credit valuation adjustment (CVA) as a percentage of the credit derivative liability calculated excluding the CVA. + References No definition available. + Details
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Namespace Prefix: | ambc_
Data Type: | num:percentItemType
Balance Type: | na
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- Details
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- Definition Fair value of the gross liabilities less the gross assets of a derivative liability or group of derivative liabilities. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 50 -Paragraph 10 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=7491637&loc=d3e13433-108611 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 45 -Paragraph 5 -URI http://asc.fasb.org/extlink&oid=6945355&loc=d3e41228-113958 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 50 -Paragraph 15 -URI http://asc.fasb.org/extlink&oid=7491637&loc=d3e13495-108611 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 45 -Paragraph 6 -URI http://asc.fasb.org/extlink&oid=6945355&loc=d3e41271-113958 + Details
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- Definition Aggregate notional amount of credit risk derivatives. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 1A -Subparagraph (d) -URI http://asc.fasb.org/extlink&oid=7476318&loc=SL5579245-113959 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Notional Amount -URI http://asc.fasb.org/extlink&oid=6519104 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 1B -URI http://asc.fasb.org/extlink&oid=7476318&loc=SL5580258-113959 + Details
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