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Loans - Additional Information (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Finance Receivable Transferred To Held For Sale [Line Items]
Loans at Carrying Amount	$ 9,203	$ 18,996
Loan impairments	0	0
VIEs [Member]
Finance Receivable Transferred To Held For Sale [Line Items]
Loans at Carrying Amount	209,807	202,696
Loans outstanding maturity date	2047	2047
Loan impairments	$ 0	$ 0
Minimum [Member]
Finance Receivable Transferred To Held For Sale [Line Items]
Interest rate on loans	4.67%	3.01%
Loans outstanding maturity date	2013-12	2013-12
Minimum [Member] | VIEs [Member]
Finance Receivable Transferred To Held For Sale [Line Items]
Interest rate on loans	5.33%	5.33%
Maximum [Member]
Finance Receivable Transferred To Held For Sale [Line Items]
Interest rate on loans	7.00%	7.00%
Loans outstanding maturity date	2026-06	2026-06
Maximum [Member] | VIEs [Member]
Finance Receivable Transferred To Held For Sale [Line Items]
Interest rate on loans	5.42%	5.42%

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- Details

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Namespace Prefix:	abk_
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X

- Definition

Interest Rate On Term Loan

+ References

No definition available.

+ Details

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Namespace Prefix:	abk_
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Period Type:	duration

X

- Definition

Loan Maturity date

+ References

No definition available.

+ Details

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Namespace Prefix:	abk_
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Balance Type:	na
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X

- Definition

Maturity Year Of Long Term Debt

+ References

No definition available.

+ Details

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X

- Definition

Amount of allowance for credit losses related to recorded investment.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 50

-Paragraph 15

-Subparagraph (a)(3)

-URI http://asc.fasb.org/extlink&oid=7512638&loc=d3e5212-111524

+ Details

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Namespace Prefix:	us-gaap_
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Balance Type:	credit
Period Type:	instant

X

- Definition

Total of loans held-for-sale and held-in-portfolio net of unearned income, allowance for loan and lease losses, if any, unamortized loan origination and other fees and costs, and purchased premiums or discounts.

+ References

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 7

-Subparagraph a

-Article 9



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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-03.7(a))

-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

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Balance Type:	debit
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