Financial Guarantee Insurance Contracts - Estimated Future Amortization Expense for Insurance Intangible Asset (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013
Amortization Of Intangible Assets [Abstract]
2013	$ 71,958
2014	127,898
2015	114,572
2016	105,052
2017	97,306
Thereafter	$ 1,104,826

- Details

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- Definition

Amount of amortization expected to be recognized after the fifth fiscal year following the latest fiscal year for insurance intangible asset, excluding goodwill.

+ References

No definition available.

+ Details

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Period Type:	instant

- Definition

Amount of amortization expected to be recognized during the remaining current fiscal year for insurance intangible asset, excluding goodwill.

+ References

No definition available.

+ Details

Name:	ambc_AmortizationOfIntangibleAssetsRemainingFiscalYear
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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of amortization expected to be recognized during the fifth fiscal year following the latest fiscal year for insurance intangible asset, excluding goodwill.

+ References

No definition available.

+ Details

Name:	ambc_AmortizationOfIntangibleAssetsYearFive
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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of amortization expected to be recognized during the fourth fiscal year following the latest fiscal year for insurance intangible asset, excluding goodwill.

+ References

No definition available.

+ Details

Name:	ambc_AmortizationOfIntangibleAssetsYearFour
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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of amortization expected to be recognized during the third fiscal year following the latest fiscal year for insurance intangible asset, excluding goodwill.

+ References

No definition available.

+ Details

Name:	ambc_AmortizationOfIntangibleAssetsYearThree
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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of amortization expected to be recognized during the second fiscal year following the latest fiscal year for insurance intangible asset, excluding goodwill.

+ References

No definition available.

+ Details

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Namespace Prefix:	ambc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant