Fresh Start Financial Statement Reporting - Schedule of Impact of Fresh Start Adjustments (Detail) (Predecessor Ambac [Member], USD $) In Thousands, unless otherwise specified	Apr. 30, 2013
Fresh-Start Adjustment [Line Items]
Deferred acquisition costs	$ (184,953)
Insurance intangible asset	1,658,972
Goodwill	514,511
Obligations under investment agreements	(1,505)
Long-term debt and accrued interest payable	(767,924)
Other liabilities	(1,837)
Asset/liability fair value adjustments impacting Reorganization items	1,228,251
Adjustment to deferred tax provision
Gain on fresh start adjustments	1,228,251
Non-variable interest entity [Member]
Fresh-Start Adjustment [Line Items]
Loans (non-VIE)	(1,575)
Variable Interest Entity [Member]
Fresh-Start Adjustment [Line Items]
VIE loans and long-term debt	$ 12,562

Fresh Start Adjustment Increase Decrease Adjustment To Deferred Tax Provision

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Amount of fresh-start adjustment to deferred acquisition costs.

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Fresh-start adjustment to loans.

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Fresh Start Adjustment, Increase (Decrease), Long Term Debt And Accrued Interest Payable

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Fresh Start Adjustment Increase Decrease Obligations Under Investment Agreements

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Fresh-start adjustments to VIE assets and liabilities.

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Fresh Start Adjustment Net Gain

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Amount of fresh-start adjustment to amortizable intangible assets.

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Amount of fresh-start adjustment to goodwill.

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The total of the amount of fresh-start adjustments to other noncurrent obligations.

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Amount of fresh-start adjustment to reorganization value in excess of amounts allocable to identifiable assets (generally due to the revaluation of assets and liabilities).

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