Background and Business Description - Additional Information (Detail)	1 Months Ended	4 Months Ended	8 Months Ended	12 Months Ended
	Apr. 30, 2013 USD ($) $ / shares shares	Apr. 30, 2013 USD ($) $ / shares shares	Dec. 31, 2013 USD ($)	Dec. 31, 2015 USD ($) Segment $ / shares shares	Dec. 31, 2014 USD ($) $ / shares Rate shares	Dec. 31, 2010 USD ($)	May. 01, 2013 USD ($) $ / shares shares
Background And Basis Of Presentation [Line Items]
Unpaid as a Percentage of Permitted Policy Claims | Rate					55.00%
Entity Incorporation, Date of Incorporation				Apr. 29, 1991	Apr. 29, 1991
Number of reportable segments | Segment				2
Par Value of Owner Trust Certificate					$ 74,794,000
Par Value of Private Placement					$ 299,175,000
Private Placement Par Value Proceeds					80.00%
Private Placement Maturity Date					Aug. 28, 2039
Interest on junior surplus notes					5.10%
Investment Warrants Expiration Date		Apr. 30, 2023
Transaction Limit					$ 5,000,000
Accrued rate of interest on outstanding policy obligations (percent)				5.10%	5.10%
Payment of permitted policy claim (percent)					25.00%
Equalizing payment on unpaid permitted policy claim (percent)					26.67%
December 2014 Payment of Deferred Amounts					$ 1,137,202,000
Capital Stock Authorized | shares	150,000,000	150,000,000
Common stock, shares authorized | shares	130,000,000	130,000,000
Common Stock, Par or Stated Value Per Share | $ / shares	$ 0.01	$ 0.01
Preferred stock, shares authorized | shares	20,000,000	20,000,000
Preferred Stock, Par or Stated Value Per Share | $ / shares	$ 0.01	$ 0.01
Common stock, shares issued | shares	45,000,000	45,000,000
Warrants issued exercise price | $ / shares	$ 16.67	$ 16.67
Mediation Agreement Cash Grant	$ 30,000,000	$ 30,000,000
Junior surplus note of Ambac Assurance Segregated Account	350,000,000	$ 350,000,000					$ 350,000,000
Common Stock Voting Restrictions					10.00%
Common Stock Voting Restriction Less One Vote					10.00%
Common Stock Transfer Restrictions					5.00%
Common Stock Additional Transfer Restrictions					5.00%
November 2014 Payment of Surplus Notes					$ 413,587,000
Ambac Assurance [Member]
Background And Basis Of Presentation [Line Items]
Net par exposure for policies allocated to the Segregated Account				$ 15,361,202,000
Issuance of secured note to segregated account						$ 2,000,000,000
Secured note maturity year						2050
Interest on the secured note accrues						4.50%
Available secured notes including capitalized interest					0
Minimum surplus amount				100,000,000
Maximum Reimbursement Of Operating Expenses	$ 5,000,000
Successor [Member]
Background And Basis Of Presentation [Line Items]
Proceeds from the sale of Junior Surplus Notes of the Segregated Account			$ 0	$ 0	$ 224,262,000
Common stock, shares authorized | shares				130,000,000	130,000,000
Common Stock, Par or Stated Value Per Share | $ / shares				$ 0.01	$ 0.01		$ 0.01
Preferred stock, shares authorized | shares				20,000,000	20,000,000
Preferred Stock, Par or Stated Value Per Share | $ / shares				$ 0.01	$ 0.01
Common stock, shares issued | shares				45,044,222	45,005,932		45,000,000
Warrants Distributed In Bankruptcy | shares	5,047,138	5,047,138					5,047,138
Warrants issued exercise price | $ / shares							$ 16.67
Two Thousand And Seventeen [Member] | Ambac Assurance [Member]
Background And Basis Of Presentation [Line Items]
Maximum Reimbursement Of Operating Expenses after 2017	$ 4,000,000