Income Taxes - Additional Information (Detail) (USD $) In Thousands, unless otherwise specified	9 Months Ended	12 Months Ended
	Sep. 30, 2011	Dec. 31, 2014	Dec. 31, 2013	Apr. 30, 2013	Dec. 31, 2012	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		5,401,573
Operating tax carryforward expiration year start		2029
Operating tax carryforward expiration year end		2034
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		1,379,082
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		4,986,206
United States [Member]
Tax Credit Carryforward [Line Items]
NOL allocated amount		167,004
United Kingdom [Member]
Tax Credit Carryforward [Line Items]
NOL allocated amount		$ 248,363