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
Mar. 31, 2017	Mar. 31, 2016
Segment Reporting Information [Line Items]
Gross Premiums Written	$ 5,584	$ (24,780)
Net premiums earned	47,613	52,800
Net Change In Fair Value Of Credit Derivatives	1,052	12,866
Reportable Geographical Components [Member] \| United States [Member]
Segment Reporting Information [Line Items]
Gross Premiums Written	(2,679)	(13,759)
Net premiums earned	40,621	46,115
Net Change In Fair Value Of Credit Derivatives	201	855
Reportable Geographical Components [Member] \| United Kingdom [Member]
Segment Reporting Information [Line Items]
Gross Premiums Written	10,727	9,352
Net premiums earned	5,263	6,388
Net Change In Fair Value Of Credit Derivatives	0	0
Reportable Geographical Components [Member] \| Other International [Member]
Segment Reporting Information [Line Items]
Gross Premiums Written	(2,464)	(20,373)
Net premiums earned	1,729	297
Net Change In Fair Value Of Credit Derivatives	$ 851	$ 12,011

Aggregate net gain (loss) on all derivative instruments recognized in earnings during the period, before tax effects.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4A
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=56946850&loc=SL5618551-113959

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Amount, after premiums ceded to other entities and premiums assumed by the entity, of financial guarantee premiums earned.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 20
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=6480758&loc=d3e6811-158387

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 605
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6486662&loc=d3e27175-158546

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 225
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-04.1)
-URI http://asc.fasb.org/extlink&oid=6879464&loc=d3e573970-122913

Reference 4: http://www.xbrl.org/2003/role/presentationRef
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-Section 50
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-URI http://asc.fasb.org/extlink&oid=6480758&loc=d3e6816-158387

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 20
-Section 50
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=6933001&loc=SL5747862-161289

Reference 6: http://www.xbrl.org/2003/role/presentationRef
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Amount of direct and assumed premiums written.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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-Topic 944
-SubTopic 605
-Section 50
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