Income Taxes Income Taxes - NOL Usage Table (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Apr. 30, 2013	Dec. 31, 2010
Net Income Loss Reconciliation [Line Items]
TierABCCredit	$ 5,000
TierACreditUsage	10,000
NOL allocated amount	4,298,770
Tolling Payment Payable to AFG	$ 70,911
Tier C Tolling Payment Payable to IRS	12.50%
Tier D Tolling Payments Payable to IRS	17.50%
Ambac Assurance [Member]
Net Income Loss Reconciliation [Line Items]
AACNetTaxableIncome	$ 877,313
AACNetTaxableIncomeFromTierA	479,000
AACNetTaxableIncomeFromTierB	398,313
Ambac [Member]
Net Income Loss Reconciliation [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
Segregated Account [Member]
Net Income Loss Reconciliation [Line Items]
Bankruptcy Claims, Amount Paid to Settle Claims		$ 100,000
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%