Basis of Presentation and Significant Accounting Policies - Additional Information (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
Dec. 31, 2012 Customer Transactions	Dec. 31, 2011
Accounting Policies [Line Items]
Discontinued Liabilities subject to compromise	$ 211,896
Liabilities subject to compromise contractual interest on debt	85,371	110,093
Weighted average risk-free rate	2.60%	2.60%
Weighted average period of future premiums	9 years 7 months 6 days	10 years
Transactions with non-investment grade internal ratings	40.00%	43.00%
Non-investment grade MBS on total premium receivable	7.00%	9.00%
Percentage of student loan transactions on total premium receivable	12.00%	11.00%
Accelerated premium revenue for retired obligations	127,628	60,249
Weighted average risk-free discount rate	1.60%	1.80%
Percentage on impaired population of loans	39.00%
Total number of sponsors	8
Number of transactions represented by sponsors	49
Amortization of deferred acquisition costs	26,825	21,328
Fair values declined below amortized cost percentage	20.00%
Future grant equity shares	16,032,551
Foreign exchange items	(175)	1,436
Breach Rate [Member]
Accounting Policies [Line Items]
Percentage on impaired population of loans	4.00%
Minimum [Member]
Accounting Policies [Line Items]
Fair values declined below amortized cost percentage	5.00%
Estimated useful lives of assets	3 years
Maximum [Member]
Accounting Policies [Line Items]
Past due premiums on policies insuring non-investment grade obligations amount	$ 500
Fair values declined below amortized cost percentage	20.00%
Estimated useful lives of assets	5 years
Risk Classification - Class II [Member]
Accounting Policies [Line Items]
Percentage of monetary default	10.00%
Risk Classification - Class III [Member] \| Minimum [Member]
Accounting Policies [Line Items]
Percentage of monetary default	50.00%

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Liabilities Subject To Compromise Not Recognized In Balance Sheet

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Number of insured transactions that have been reviewed to ascertain whether the loans underlying the insured RMBS transactions conform to the representation and warranties with respect to the securitized loans.

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Number of sponsors that represent insured transactions are being reviewed.

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Percentage Decline In Market Value Below Amortization Cost

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Percentage of financial guarantee premiums receivable related to Student Loan insured transactions with non-investment grade internal ratings.

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Represents the percentage of the adverse loan sample subset versus the principal balance of the impaired population of loans.

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Represents the percentage of the adverse loan sample subset versus the principal balance of the original loans in pool.

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Percentage of financial guarantee premiums receivable related to insured transactions with non-investment grade internal ratings.

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Past due premiums on policies insuring internally rated non-investment grade obligations.

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Percentage of probability of loss or claim payment over the life of the insured transaction(s) within the related risk classification.

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The number of shares available for future grant under stock compensation plans.

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The amount of contractual interest expense on prepetition liabilities not included in the statement of operations.

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Amount of deferred policy acquisition costs charged to expense in the period, generally in proportion to related revenue earned, estimated gross profits, or over the customer relationship or some other period.

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This element represents the amount of premium revenue on financial guarantee insurance contracts recognized during the period that was accelerated for revenue recognition purposes.

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This element represents the weighted average risk free rate used to discount the claim liability related to financial guarantee insurance contracts.

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Weighted average period over which premium receivable for financial guarantee insurance contracts is collected where premium is received over the contract period, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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This element represents the weighted average risk free rate used to discount the premiums expected to be collected for financial guarantee insurance contracts where the premium is to be received over the contract period.

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The aggregate foreign currency transaction gain (loss) (both realized and unrealized) included in determining net income for the reporting period. Excludes foreign currency transactions designated as hedges of net investment in a foreign entity and intercompany foreign currency transactions that are of a long-term nature, when the entities to the transaction are consolidated, combined, or accounted for by the equity method in the reporting enterprise's financial statements. For certain enterprises, primarily banks, that are dealers in foreign exchange, foreign currency transaction gains (losses) may be disclosed as dealer gains (losses).

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Useful life of long lived, physical assets used in the normal conduct of business and not intended for resale, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. Examples include, but not limited to, land, buildings, machinery and equipment, office equipment, furniture and fixtures, and computer equipment.

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