Financial Guarantee Insurance Contracts - Summary of Rollforward of RMBS Subrogation, by Estimation Approach (Detail) - Successor [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Subrogation By Estimation Approach [Roll Forward]
Discounted RMBS subrogation (gross of reinsurance), beginning balance	$ 2,829,575	$ 2,523,540	$ 2,206,598
Changes recognized
Additional Transactions Reviewed Changes in RMBS Subrogation			24,565
Changes in Estimation Approach In Rmbs Subrogation			198,875
Impact of sponsor actions	(995,000)		(146,270)
Other Changes Rmbs Subrogation	72,460	306,035	239,772
Discounted RMBS subrogation (gross of reinsurance), ending balance	1,907,035	2,829,575	2,523,540
Random Samples [Member]
Subrogation By Estimation Approach [Roll Forward]
Discounted RMBS subrogation (gross of reinsurance), beginning balance	2,829,575	2,523,540	953,825
Changes recognized
Additional Transactions Reviewed Changes in RMBS Subrogation			24,565
Changes in Estimation Approach In Rmbs Subrogation			1,417,556
Impact of sponsor actions	(995,000)		(146,270)
Other Changes Rmbs Subrogation	72,460	306,035	273,864
Discounted RMBS subrogation (gross of reinsurance), ending balance	1,907,035	2,829,575	2,523,540
Adverse Samples [Member]
Subrogation By Estimation Approach [Roll Forward]
Discounted RMBS subrogation (gross of reinsurance), beginning balance	0	0	1,252,773
Changes recognized
Additional Transactions Reviewed Changes in RMBS Subrogation			0
Changes in Estimation Approach In Rmbs Subrogation			(1,218,681)
Impact of sponsor actions	0		0
Other Changes Rmbs Subrogation	0	0	(34,092)
Discounted RMBS subrogation (gross of reinsurance), ending balance	$ 0	$ 0	$ 0