Financial Guarantee Insurance Contracts - Summary of Loss Reserve Roll-Forward, Net of Subrogation Recoverable and Reinsurance (Detail) - Successor [Member] - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015	Dec. 31, 2015
Loss And Loss Adjustment Expense Reserves [Line Items]
Ceded Loss And Loss Expenses Paid Not Yet Recovered	$ (1,404)	$ 4,974			$ (60)
Policyholder Benefits and Claims Incurred, Ceded	(1,847)	(3,219)	$ (7,607)	$ (23,821)
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]
Beginning gross loss and loss expense reserves			2,858,813	3,798,733
Less reinsurance on loss and loss expense reserves			44,059	100,355
Beginning balance of net loss and loss expense reserves			2,814,754	3,698,378
Current year:
ambc_LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseIncurredClaimsCurrentYear			12	737
Total current year			12	737
Prior years:
Change in previously established loss and loss expense reserves, gross of RMBS subrogation and net of reinsurance			(157,403)	(262,962)
Claim and loss expense (payments) recoveries, net of subrogation and reinsurance			(1,011,957)	88,387
Change in previously established RMBS subrogation recoveries, net of reinsurance			(48,647)	(32,785)
Liability For Unpaid Claims And Claims Adjustment Expense Change In Loss Reserves Prior Year			805,907	(384,134)
Net change in loss and loss expense reserves			805,919	(383,397)
Liability for Unpaid Claims and Claims Adjustment Expense, Net	3,620,673	3,314,981	2,814,754	3,698,378	$ 2,814,754
Add reinsurance on loss and loss expense reserves	30,108	71,031	30,108	71,031
Ending gross loss and loss expense reserves	$ 3,650,781	$ 3,386,012	$ 3,650,781	$ 3,386,012