Income Taxes Income Taxes - NOL Usage Table (Details) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended		24 Months Ended
	Sep. 30, 2011	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2016
Net Income Loss Reconciliation [Line Items]
TierABCCredit			$ 5,000
TierABCredit			(10,000)
NOL allocated amount		$ 4,027,329		$ 4,027,329
Tolling Payment to AFG			71,454
Tolling Payment Payable to AFG		$ 28,691		$ 28,691
Tier C Tolling Payment Payable to IRS		12.50%		12.50%
Tier D Tolling Payments Payable to IRS		17.50%		17.50%
Income Tax Examination, Penalties and Interest Accrued	$ 3,650,000
Ambac Assurance [Member]
Net Income Loss Reconciliation [Line Items]
AACNetTaxableIncome		$ 1,086,124	877,313
NOL allocated amount		2,563,876		$ 2,563,876
AACNetTaxableIncomeFromTierA		479,000	479,000
AACNetTaxableIncomeFromTierB		204,932	$ 402,192	607,124
Percentage Of Notional Federal Tax Liability	25.00%
AFG [Member]
Net Income Loss Reconciliation [Line Items]
NOL allocated amount		1,389,359		1,389,359
Percentage Of Notional Federal Tax Liability	50.00%
Tier A [Member]
Net Income Loss Reconciliation [Line Items]
NOL allocated amount		$ 479,000		479,000
NOL applicable percentage		15.00%
Tier B [Member]
Net Income Loss Reconciliation [Line Items]
NOL allocated amount		$ 1,057,000		1,057,000
NOL applicable percentage		40.00%
Tier C [Member]
Net Income Loss Reconciliation [Line Items]
NOL allocated amount		$ 1,057,000		1,057,000
NOL applicable percentage		10.00%
Tier D [Member]
Net Income Loss Reconciliation [Line Items]
NOL allocated amount		$ 1,057,000		$ 1,057,000
NOL applicable percentage		15.00%