Financial Guarantee Insurance Contracts - Effect of Reinsurance on Premiums Written and Earned (Detail) - Successor [Member] - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
Direct Premiums Written									$ 14,313	$ 53,837	$ 37,572
Assumed Reinsurance Premiums Written									0	0	0
Ceded Reinsurance Premiums Written									2,104	8,772	3,001
Premiums written, net of reinsurance									12,209	45,065	34,571
Direct Premiums Earned									190,496	215,564	336,025
Assumed Reinsurance Premiums Earned									106	85	87
Ceded Reinsurance Premiums Earned									15,325	18,362	23,517
Reinsurance on premiums earned, Net	$ 31,523	$ 52,989	$ 43,152	$ 47,613	$ 49,867	$ 53,218	$ 41,402	$ 52,800	$ 175,277	$ 197,287	$ 312,595