Income Taxes - Additional Information (Detail) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2011	Dec. 31, 2015	Dec. 31, 2013	Dec. 31, 2014	Apr. 30, 2013	Dec. 31, 2010
Tax Credit Carryforward [Line Items]
Unrecognized Tax Benefits, Interest on Income Taxes Accrued		$ 0	$ 0	$ 0	$ 0
Income Tax Examination, Penalties and Interest Accrued	$ 3,650,000
NOL allocated amount		4,298,770
Net Operating Loss Carry Forwards Reduced For Cancellation Of Indebtedness Income And Interest Expense			$ 816,380
Percentage Of Notional Federal Tax Liability	25.00%
AFG [Member]
Tax Credit Carryforward [Line Items]
NOL allocated amount		1,382,109
Ambac [Member]
Tax Credit Carryforward [Line Items]
Bankruptcy Claims, Amount Paid to Settle Claims					1,900
Amount Of Loss Carry Forward Relinquish By Which Loss Carry Forward Exceed						$ 3,400,000
Amount Of Loss Carryforward Relinquishment						$ 1,059,988
Segregated Account [Member]
Tax Credit Carryforward [Line Items]
Bankruptcy Claims, Amount Paid to Settle Claims					$ 100,000
U. S. Federal Net Operating Tax [Member]
Tax Credit Carryforward [Line Items]
NOL allocated amount		4,154,786
United States [Member]
Tax Credit Carryforward [Line Items]
NOL allocated amount		129,048
United Kingdom [Member]
Tax Credit Carryforward [Line Items]
NOL allocated amount		$ 14,936
Minimum [Member]
Tax Credit Carryforward [Line Items]
Operating Loss Carryforwards, Expiration Date		Dec. 31, 2029
Maximum [Member]
Tax Credit Carryforward [Line Items]
Operating Loss Carryforwards, Expiration Date		Dec. 31, 2034