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	Dec. 31, 2017 USD ($)
Future premiums expected to be collected, March 31, 2018	$ 16,923
Future premiums expected to be collected, June 30. 2018	13,801
Future premiums expected to be collected, September 30, 2018	14,779
Future premiums expected to be collected, December 31, 2018	13,282
Future premiums expected to be collected, December 31, 2019	55,203
Future premiums expected to be collected, December 31, 2020	52,282
Future premiums expected to be collected, December 31, 2021	45,848
Future premiums expected to be collected, December 31, 2022	43,678
Future premiums expected to be collected, December 31, 2027	193,190
Future premiums expected to be collected, December 31, 2032	150,385
Future premiums expected to be collected, December 31, 2037	82,597
Future premiums expected to be collected, December 31, 2042	29,169
Future premiums expected to be collected, December 31, 2047	13,599
Future premiums expected to be collected, December 31, 2052	3,586
Future premiums expected to be collected, December 31, 2057	92
Future premiums expected to be collected, Total	728,414
Future expected premium to be earned, net of reinsurance, March 31, 2018	17,561
Future expected premiums to be earned, net of reinsurance, June 30, 2018	17,294
Future expected premiums to be earned, net of reinsurance, September 30, 2018	16,604
Future expected premiums to be earned, net of reinsurance, December 31, 2018	16,150
Future expected premiums to be earned, net of reinsurance, December 31, 2019	61,368
Future expected premiums to be earned, net of reinsurance, December 31, 2020	57,263
Future expected premiums to be earned, net of reinsurance, December 31, 2021	52,149
Future expected premiums to be earned, net of reinsurance, December 31, 2022	48,447
Future expected premiums to be earned, net of reinsurance, December 31, 2027	197,446
Future expected premiums to be earned, net of reinsurance, December 31, 2032	131,682
Future expected premiums to be earned, net of reinsurance, December 31, 2037	72,520
Future expected premiums to be earned, net of reinsurance, December 31, 2042	24,833
Future expected premiums to be earned, net of reinsurance, December 31, 2047	12,694
Future expected premiums to be earned, net of reinsurance, December 31, 2052	4,651
Future expected premiums to be earned, net of reinsurance, December 31, 2057	298
Future expected premiums to be earned, net of reinsurance, Total	$ 730,960