Financial Guarantee Insurance Contracts - Summarized Future Gross Undiscounted Premiums Expected to be Collected, and Future Expected Premiums Earned, Net of Reinsurance (Detail) - Successor [Member] $ in Thousands	Mar. 31, 2017 USD ($)
Future premiums expected to be collected, June 30. 2017	$ 15,490
Future premiums expected to be collected, September 30, 2017	16,958
Future premiums expected to be collected, December 31, 2017	14,583
Future premiums expected to be collected, December 31, 2018	61,045
Future premiums expected to be collected, December 31, 2019	57,574
Future premiums expected to be collected, December 31, 2020	54,725
Future premiums expected to be collected, December 31, 2021	48,636
Future premiums expected to be collected, December 31, 2026	215,417
Future premiums expected to be collected, December 31, 2031	172,005
Future premiums expected to be collected, December 31, 2036	101,505
Future premiums expected to be collected, December 31, 2041	35,221
Future premiums expected to be collected, December 31, 2046	16,921
Future premiums expected to be collected, December 31, 2051	5,250
Future premiums expected to be collected, December 31, 2056	239
Future premiums expected to be collected, Total	815,569
Future expected premiums to be earned, net of reinsurance, June 30, 2017	26,449
Future expected premiums to be earned, net of reinsurance, September 30, 2017	23,676
Future expected premiums to be earned, net of reinsurance, December 31, 2017	20,442
Future expected premiums to be earned, net of reinsurance, December 31, 2018	73,108
Future expected premiums to be earned, net of reinsurance, December 31, 2019	66,576
Future expected premiums to be earned, net of reinsurance, December 31, 2020	62,413
Future expected premiums to be earned, net of reinsurance, December 31, 2021	57,214
Future expected premiums to be earned, net of reinsurance, December 31, 2026	233,977
Future expected premiums to be earned, net of reinsurance, December 31, 2031	157,264
Future expected premiums to be earned, net of reinsurance, December 31, 2036	88,021
Future expected premiums to be earned, net of reinsurance, December 31, 2041	30,593
Future expected premiums to be earned, net of reinsurance, December 31, 2046	14,783
Future expected premiums to be earned, net of reinsurance, December 31, 2051	6,148
Future expected premiums to be earned, net of reinsurance, December 31, 2056	686
Future expected premiums to be earned, net of reinsurance, Total	$ 861,350