Segment Information - Schedule of Gross Premiums Written, Net Premiums Earned and Net Change in Fair Value of Credit Derivatives (Detail) - Successor [Member] - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Segment Reporting Information [Line Items]
Gross Premiums Written	$ 14,473	$ 10,543	$ (4,041)	$ (24,780)	$ (18,732)	$ (8,710)	$ (11,192)	$ (1,062)	$ (53,837)	$ (37,572)	$ 288,310
Net premiums earned	49,867	53,218	41,402	52,800	114,463	71,535	60,879	65,718	197,287	312,595	246,360
Net Change In Fair Value Of Credit Derivatives	$ 1,552	$ 1,733	$ 3,955	$ 12,866	$ (3,045)	$ 36,952	$ 10,293	$ (2,499)	20,106	41,701	23,906
Reportable Geographical Components [Member] | United States [Member]
Segment Reporting Information [Line Items]
Gross Premiums Written									(35,686)	(13,028)	(46,279)
Net premiums earned									168,646	229,658	197,154
Net Change In Fair Value Of Credit Derivatives									1,828	39,633	8,669
Reportable Geographical Components [Member] | United Kingdom [Member]
Segment Reporting Information [Line Items]
Gross Premiums Written									10,892	3,652	(221,516)
Net premiums earned									24,470	68,799	31,672
Net Change In Fair Value Of Credit Derivatives									0	0	0
Reportable Geographical Components [Member] | Other International [Member]
Segment Reporting Information [Line Items]
Gross Premiums Written									(29,043)	(28,196)	(20,515)
Net premiums earned									4,171	14,138	17,534
Net Change In Fair Value Of Credit Derivatives									$ 18,278	$ 2,068	$ 15,237