Financial Guarantee Insurance Contracts - Summary of Balance of RMBS Subrogation Recoveries and Related Claim Liabilities, by Estimation Approach (Detail) (Successor [Member], USD $) In Thousands, unless otherwise specified	4 Months Ended	8 Months Ended	12 Months Ended
	Apr. 30, 2013	Dec. 31, 2013	Dec. 31, 2014	Dec. 31, 2012	Dec. 31, 2011
Schedule Of Balance Of Rmbs Subrogation Recoveries And Related Claim Liabilities By Estimation Approach [Line Items]
Gross loss reserve before subrogation recoveries		$ 3,163,772	$ 1,897,426
Subrogation recoveries	2,482,918	2,206,598	2,523,540	2,523,225	2,720,266
Gross loss reserve after subrogation recoveries		957,174	(626,114)
Additional Transactions Reviewed Changes in RMBS Subrogation	0	2,451	24,565	18,981
Changes in Estimation Approach In Rmbs Subrogation	0	0	198,875	0
Impact Of Sponsor Actions In Residential Mortgage Backed Securities Subrogation	(54,195)	98	(146,270)	0
Other Changes Rmbs Subrogation	13,888	(278,869)	239,772	(216,057)
Adverse Loans Repurchased By Sponsor Change in Rmbs Subrogation	0	0		35
Adverse Samples [Member]
Schedule Of Balance Of Rmbs Subrogation Recoveries And Related Claim Liabilities By Estimation Approach [Line Items]
Gross loss reserve before subrogation recoveries		2,084,911
Subrogation recoveries		1,252,773
Gross loss reserve after subrogation recoveries		832,138
Random Samples [Member]
Schedule Of Balance Of Rmbs Subrogation Recoveries And Related Claim Liabilities By Estimation Approach [Line Items]
Gross loss reserve before subrogation recoveries		1,078,861	1,897,426
Subrogation recoveries		953,825	2,523,540
Gross loss reserve after subrogation recoveries		125,036	(626,114)
Adverse Samples [Member]
Schedule Of Balance Of Rmbs Subrogation Recoveries And Related Claim Liabilities By Estimation Approach [Line Items]
Subrogation recoveries	1,478,666	1,252,773	0	1,442,817	1,457,472
Additional Transactions Reviewed Changes in RMBS Subrogation	0	0	0	(35,486)
Changes in Estimation Approach In Rmbs Subrogation	0	0	(1,218,681)	0
Impact Of Sponsor Actions In Residential Mortgage Backed Securities Subrogation	0	98	0	0
Other Changes Rmbs Subrogation	35,849	(225,991)	(34,092)	20,796
Adverse Loans Repurchased By Sponsor Change in Rmbs Subrogation	0	0		35
Random Samples [Member]
Schedule Of Balance Of Rmbs Subrogation Recoveries And Related Claim Liabilities By Estimation Approach [Line Items]
Subrogation recoveries	1,004,252	953,825	2,523,540	1,080,408	1,262,794
Additional Transactions Reviewed Changes in RMBS Subrogation	0	2,451	24,565	54,467
Changes in Estimation Approach In Rmbs Subrogation	0	0	1,417,556	0
Impact Of Sponsor Actions In Residential Mortgage Backed Securities Subrogation	(54,195)	0	(146,270)	0
Other Changes Rmbs Subrogation	(21,961)	(52,878)	273,864	(236,853)
Adverse Loans Repurchased By Sponsor Change in Rmbs Subrogation	$ 0	$ 0		$ 0