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Long-Term Debt - Carrying Value of Long-Term Debt (Parenthetical) (Detail)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Debt Instrument [Line Items]
Percentage of debt instrument	6.65%
Ambac Assurance Corporation [Member] | 5.1% surplus notes, general account, due 2020 [Member]
Debt Instrument [Line Items]
Percentage of debt instrument	5.10%	5.10%
Debt instrument due	2020	2020
Ambac Assurance Corporation [Member] | 5.1% surplus notes, segregated account, due 2020 [Member]
Debt Instrument [Line Items]
Percentage of debt instrument	5.10%	5.10%
Debt instrument due	2020	2020
Ambac Assurance Corporation [Member] | 5.1% junior surplus notes, segregated account, due 2020 [Member]
Debt Instrument [Line Items]
Percentage of debt instrument	5.10%	5.10%
Debt instrument due	2020	2020

X

- Definition

Debt Instruments Maturity Year

+ References

No definition available.

+ Details

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X

- Definition

Interest rate stated in the contractual debt agreement.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 22

-Article 5



Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.22(a)(1))

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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