Financial Guarantee Insurance Contracts - Summary of Rollforward of RMBS Subrogation, by Estimation Approach (Detail) (Successor [Member], USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Subrogation By Estimation Approach [Roll Forward]
Discounted RMBS subrogation (gross of reinsurance), beginning balance	$ 2,523,540	$ 2,206,598
Changes recognized
Changes in Estimation Approach In Rmbs Subrogation	0	0
Impact of sponsor actions	0	0
Other Changes Rmbs Subrogation	44,813	17,697
Discounted RMBS subrogation (gross of reinsurance), ending balance	2,568,353	2,224,295
Random Samples [Member]
Subrogation By Estimation Approach [Roll Forward]
Discounted RMBS subrogation (gross of reinsurance), beginning balance	2,523,540	953,825
Changes recognized
Changes in Estimation Approach In Rmbs Subrogation	0	0
Impact of sponsor actions	0	0
Other Changes Rmbs Subrogation	44,813	51,789
Discounted RMBS subrogation (gross of reinsurance), ending balance	2,568,353	1,005,614
Adverse Samples [Member]
Subrogation By Estimation Approach [Roll Forward]
Discounted RMBS subrogation (gross of reinsurance), beginning balance	0	1,252,773
Changes recognized
Changes in Estimation Approach In Rmbs Subrogation	0	0
Impact of sponsor actions	0	0
Other Changes Rmbs Subrogation	0	(34,092)
Discounted RMBS subrogation (gross of reinsurance), ending balance	$ 0	$ 1,218,681