Financial Guarantee Insurance Contracts - Summary of Loss Reserve Roll-Forward, Net of Subrogation Recoverable and Reinsurance (Detail) € in Thousands, $ in Thousands	9 Months Ended
	Sep. 30, 2017 USD ($)	Sep. 30, 2017 EUR (€)	Sep. 30, 2016 USD ($)	Sep. 30, 2016 EUR (€)	Sep. 30, 2017 USD ($)	Dec. 31, 2016 USD ($)	Sep. 30, 2016 USD ($)
Successor [Member]
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]
Beginning gross loss and loss expense reserves	$ 3,696,038		$ 2,858,813
Less reinsurance on loss and loss expense reserves	30,767		44,059
Beginning balance of net loss and loss expense reserves	3,665,271		2,814,754
Current Year Claims and Claims Adjustment Expense	5,328		11,033
Prior Year Claims and Claims Adjustment Expense	405,589		(238,015)
Liability for Unpaid Claims and Claims Adjustment Expense, Incurred Claims	410,917		(226,982)
Claim and loss expense payments, net of subrogation and reinsurance	(330)		(2,056)
Claim and loss expense (payments) recoveries, net of subrogation and reinsurance	(148,082)		950,810
Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid	148,412		(948,754)
Liability for Unpaid Claims and Claims Adjustment Expense, Foreign Currency Translation Gain (Loss)	26,556		(56,910)
Liability for Unpaid Claims and Claims Adjustment Expense, Net	3,665,271		2,814,754		$ 3,954,332	$ 3,665,271	$ 3,479,616
Add reinsurance on loss and loss expense reserves	46,023		24,298
Ending gross loss and loss expense reserves	4,000,355		3,503,914
Policyholder Benefits and Claims Incurred, Ceded	21,189		(11,990)
Net Incurred RMBS Subrogation Recoveries	(62,451)		87,310
Ceded Loss And Loss Expenses Paid Not Yet Recovered					$ (47)	$ (349)	$ 143
Euro Member Countries, Euro
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]
Ending gross loss and loss expense reserves	$ 21,142	€ 17,891	$ 17,029	€ 15,153