Income Taxes Income Taxes - NOL Usage Table (Details) $ in Millions	12 Months Ended
	Dec. 31, 2023 USD ($)
Net Income Loss Reconciliation [Line Items]
NOL allocated amount	$ 3,400
Ambac Assurance [Member]
Net Income Loss Reconciliation [Line Items]
NOL allocated amount	1,760
AFG [Member]
Net Income Loss Reconciliation [Line Items]
NOL allocated amount	$ 1,640
Minimum [Member] | Ambac Assurance [Member]
Net Income Loss Reconciliation [Line Items]
Operating Loss Carryforwards, Expiration Date	Dec. 31, 2030
Maximum [Member] | Ambac Assurance [Member]
Net Income Loss Reconciliation [Line Items]
Operating Loss Carryforwards, Expiration Date	Dec. 31, 2042