Background and Business Description - Additional Information (Detail) - Jun. 30, 2015	USD ($) Segment
Background And Basis Of Presentation [Line Items]
Entity Incorporation, Date of Incorporation	Apr. 29, 1991
Number of reportable segments | Segment	2
Percentage of Total Exposure That Is Held By Counterparty	10.00%
In Connection With An Exploratory Discussion With One Counterparty-The Percentage Of The Counterparty’s Exposure That Would Be Paid In Cash	25.00%
InConnectionWithAnExploratoryDiscussionWithOneCounterpart-TheDiscount(to par)OfTheCounterpartysExposureThatWouldBeAgreedInOrderToEffectATransactionAndIssueNewSurplusNotesPayingA7%CouponAndDueIn2020	5.00%
In Connection With An Exploratory Discussion With One Counterparty, The Coupon Rate On New Surplus Notes That Might Be Issued	7.00%
In Connection With An Exploratory Discussion With One Counterparty-The Maturity Date On New Surplus Notes That Might Be Issued	2020
Ambac Assurance [Member]
Background And Basis Of Presentation [Line Items]
Net par exposure for policies allocated to the Segregated Account	$ 17,415,876,000
Minimum surplus amount	100,000,000
Statutory Accounting Practices, Statutory Capital and Surplus, Balance	$ 235,230,000