Income Taxes Income Taxes - NOL Usage Table (Details) - USD ($) $ in Thousands	9 Months Ended		12 Months Ended
	Sep. 30, 2016	Sep. 30, 2011	Dec. 31, 2015
Net Income Loss Reconciliation [Line Items]
Income Tax Examination, Penalties and Interest Accrued	$ 3,650,000
Tolling Payment Payable to AFG	19,066		$ 70,911
AdditionalTollingPaymentPayabletoAFG			543
TierABCCredit	10,000
TierACreditUsage	5,000
NOL allocated amount	4,110,272
Ambac Assurance [Member]
Net Income Loss Reconciliation [Line Items]
Percentage Of Notional Federal Tax Liability		25.00%
AACNetTaxableIncome	1,013,502		877,313
NOL allocated amount	2,636,498
AACNetTaxableIncomeFromTierA			479,000
AACNetTaxableIncomeFromTierB	136,189		398,313
AdditionalAACNetTaxableIncomeFromTierB			$ 3,879
AFG [Member]
Net Income Loss Reconciliation [Line Items]
Percentage Of Notional Federal Tax Liability		50.00%
Tier A [Member]
Net Income Loss Reconciliation [Line Items]
NOL allocated amount	$ 479,000
NOL applicable percentage	15.00%
Tier B [Member]
Net Income Loss Reconciliation [Line Items]
NOL allocated amount	$ 1,057,000
NOL applicable percentage	40.00%
Tier C [Member]
Net Income Loss Reconciliation [Line Items]
NOL allocated amount	$ 1,057,000
NOL applicable percentage	10.00%
Tier D [Member]
Net Income Loss Reconciliation [Line Items]
NOL allocated amount	$ 1,057,000
NOL applicable percentage	15.00%