Background and Business Description - Additional Information (Detail) (USD $)	3 Months Ended	12 Months Ended
	Mar. 31, 2015 Segment	Dec. 31, 2014	Apr. 30, 2013
Background And Basis Of Presentation [Line Items]
Entity Incorporation, Date of Incorporation	Apr. 29, 1991
Number of reportable segments	2
Investment Warrants Expiration Date		Apr. 30, 2023
Payment of permitted policy claim (percent)		25.00%
Common stock, shares authorized	130,000,000	130,000,000
Common Stock, Par or Stated Value Per Share	$ 0.01	$ 0.01	$ 0.01
Preferred stock, shares authorized	20,000,000	20,000,000
Preferred Stock, Par or Stated Value Per Share	$ 0.01	$ 0.01
Common stock, shares issued	45,006,057	45,005,932
Warrants Distributed In Bankruptcy			5,047,138
Warrants issued exercise price			$ 16.67
Ambac Assurance [Member]
Background And Basis Of Presentation [Line Items]
Net par exposure for policies allocated to the Segregated Account	$ 18,052,539,000
Minimum surplus amount	100,000,000
Segregated Account [Member]
Background And Basis Of Presentation [Line Items]
Insurance Liabilities Not Assumed	$ 26,169,000
Successor [Member]
Background And Basis Of Presentation [Line Items]
Common stock, shares issued			45,000,000
Warrants Distributed In Bankruptcy			5,047,138