Financial Guarantee Insurance Contracts - Additional Information (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended			12 Months Ended
	Mar. 31, 2015	Dec. 31, 2014	Mar. 31, 2014	Dec. 31, 2014	Dec. 31, 2013
Insurance [Line Items]
Estimated Future Premium Payments Weighted Average Discounted Rate	2.50%	2.70%		2.70%
Weighted average period of future premiums	9 years 7 months 6 days			10 years 1 month 6 days
Transactions with non-investment grade internal ratings	32.00%	32.00%
Non-investment grade RMBS on total premiums receivable	7.00%	7.00%
Percentage of student loan transactions on total premium receivables	7.00%	8.00%
Uncollectable premium receivables	$ 17,082	$ 17,780		$ 17,780
Past due premiums on policies insuring non-investment grade obligations amount	500
Accelerated premium revenue for retired obligations	22,852		25,114
Losses and loss expense reserves ceded to reinsurers	74,519	100,355		100,355
Subrogation recoveries	2,568,353	2,523,540		2,523,540
Subrogation recoveries, net of reinsurance	2,540,710	2,496,515		2,496,515
Accumulated amortization on insurance intangible asset	283,773	249,205		249,205
Successor [Member]
Insurance [Line Items]
Reinsurance Payable	59,268	60,436		60,436
Reinsurance recoveries of losses included in losses and loss expenses	20,601		10,559
Losses and loss expense reserves ceded to reinsurers	74,519	100,355	111,303	100,355	122,357
Intangible amortization expense	37,432		31,714
Insurance intangible asset	1,347,295	1,410,920		1,410,920
Successor [Member] | Insurance Intangible Asset [Member]
Insurance [Line Items]
Intangible amortization expense	$ 37,432		$ 31,714
Loss Reserves [Member]
Insurance [Line Items]
Weighted average risk-free rate used to discount loss reserves	2.10%			2.30%