Fresh Start Financial Statement Reporting - Schedule of Calculation of Pre-Tax Gain, Recorded as Reorganization on Consolidated Statement of Total Comprehensive Income (Parenthetical) (Detail) (USD $)	Dec. 31, 2014	Dec. 31, 2013	Apr. 30, 2013
Extinguishment of Debt [Line Items]
Enterprise value			$ 185,000,000
Common stock			450,000us-gaap_CommonStockValue
Common stock, shares issued	45,005,932us-gaap_CommonStockSharesIssued	45,003,461us-gaap_CommonStockSharesIssued	45,000,000us-gaap_CommonStockSharesIssued
Common stock, par value	$ 0.01	$ 0.01	$ 0.01
Additional paid-in capital			184,550,000us-gaap_AdditionalPaidInCapital
Additional paid-in capital allocated to warrants			11,437ambc_AdditionalPaidInCapitalWarrants
Number of warrants issued			5,047,138ambc_ClassOfWarrantIssued
Additional paid-in capital attributable to common stock			173,113
Successor [Member]
Extinguishment of Debt [Line Items]
Common stock	450,000	450,000	450,000
Common stock, shares issued			45,000,000
Additional paid-in capital	$ 189,138,000	$ 185,672,000

Fresh Start Financial Statement Reporting - Schedule of Calculation of Pre-Tax Gain, Recorded as Reorganization on Consolidated Statement of Total Comprehensive Income (Parenthetical) (Detail) (USD $)

Dec. 31, 2014

Dec. 31, 2013

Apr. 30, 2013

Extinguishment of Debt [Line Items]

Enterprise value

$ 185,000,000ambc_PlanOfReorganizationEnterpriseValue

Common stock

450,000us-gaap_CommonStockValue

Common stock, shares issued

45,005,932us-gaap_CommonStockSharesIssued

45,003,461us-gaap_CommonStockSharesIssued

45,000,000us-gaap_CommonStockSharesIssued

Common stock, par value

$ 0.01us-gaap_CommonStockParOrStatedValuePerShare

Additional paid-in capital

184,550,000us-gaap_AdditionalPaidInCapital

Additional paid-in capital allocated to warrants

11,437ambc_AdditionalPaidInCapitalWarrants

Number of warrants issued

5,047,138ambc_ClassOfWarrantIssued

Additional paid-in capital attributable to common stock

173,113us-gaap_AdditionalPaidInCapitalCommonStock

Successor [Member]

Extinguishment of Debt [Line Items]

Common stock

450,000us-gaap_CommonStockValue
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= us-gaap_SuccessorMember

Common stock, shares issued

45,000,000us-gaap_CommonStockSharesIssued
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= us-gaap_SuccessorMember

Additional paid-in capital

$ 189,138,000us-gaap_AdditionalPaidInCapital
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= us-gaap_SuccessorMember

$ 185,672,000us-gaap_AdditionalPaidInCapital
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Additional Paid In Capital Warrants

+ References

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- Definition

Class Of Warrant Issued

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- Definition

Plan Of Reorganization Enterprise Value

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No definition available.

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- Definition

Excess of issue price over par or stated value of the entity's capital stock and amounts received from other transactions involving the entity's stock or stockholders. Includes adjustments to additional paid in capital. Some examples of such adjustments include recording the issuance of debt with a beneficial conversion feature and certain tax consequences of equity instruments awarded to employees. Use this element for the aggregate amount of additional paid-in capital associated with common and preferred stock. For additional paid-in capital associated with only common stock, use the element additional paid in capital, common stock. For additional paid-in capital associated with only preferred stock, use the element additional paid in capital, preferred stock.

+ References

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 31

-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 210.5-02.30(a)(1))

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

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- Definition

Value received from shareholders in common stock-related transactions that are in excess of par value or stated value and amounts received from other stock-related transactions. Includes only common stock transactions (excludes preferred stock transactions). May be called contributed capital, capital in excess of par, capital surplus, or paid-in capital.

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- Definition

Face amount or stated value per share of common stock.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.29)

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

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 30

-Article 5

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- Definition

Total number of common shares of an entity that have been sold or granted to shareholders (includes common shares that were issued, repurchased and remain in the treasury). These shares represent capital invested by the firm's shareholders and owners, and may be all or only a portion of the number of shares authorized. Shares issued include shares outstanding and shares held in the treasury.

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- Definition

Aggregate par or stated value of issued nonredeemable common stock (or common stock redeemable solely at the option of the issuer). This item includes treasury stock repurchased by the entity. Note: elements for number of nonredeemable common shares, par value and other disclosure concepts are in another section within stockholders' equity.

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