Income Taxes (Details 3) - USD ($) $ in Millions		Dec. 31, 2015	Dec. 31, 2014
Deferred tax assets:
Federal net operating loss carryforwards		$ 50	$ 51
Foreign underwriting losses		77	56
Capital loss carryforwards		32	0
Insurance claims and reserves		713	757
Employee benefits		115	107
Other, net		29	15
Total deferred tax assets before valuation allowance		1,016	986
Valuation allowance against deferred tax assets		(130)	(109)
Total deferred tax assets		886	877
Deferred tax liabilities:
Subsidiaries not in AFG’s tax return	[1]	(63)	(61)
Investment securities		(258)	(663)
Deferred policy acquisition costs		(336)	(178)
Total deferred tax liabilities		(657)	(902)
Net deferred tax asset (liability)		229
Net deferred tax asset (liability)			(25)
Excluding Unrealized Gains [Member]
Deferred tax assets:
Federal net operating loss carryforwards		50	51
Foreign underwriting losses		77	56
Capital loss carryforwards		32	0
Insurance claims and reserves		691	682
Employee benefits		115	107
Other, net		33	26
Total deferred tax assets before valuation allowance		998	922
Valuation allowance against deferred tax assets		(130)	(109)
Total deferred tax assets		868	813
Deferred tax liabilities:
Subsidiaries not in AFG’s tax return	[1]	(63)	(61)
Investment securities		23	(6)
Deferred policy acquisition costs		(418)	(364)
Total deferred tax liabilities		(458)	(431)
Net deferred tax asset (liability)		410	382
Impact of Unrealized Gains [Member]
Deferred tax assets:
Federal net operating loss carryforwards		0	0
Foreign underwriting losses		0	0
Capital loss carryforwards		0	0
Insurance claims and reserves		22	75
Employee benefits		0	0
Other, net		(4)	(11)
Total deferred tax assets before valuation allowance		18	64
Valuation allowance against deferred tax assets		0	0
Total deferred tax assets		18	64
Deferred tax liabilities:
Subsidiaries not in AFG’s tax return	[1]	0	0
Investment securities		(281)	(657)
Deferred policy acquisition costs		82	186
Total deferred tax liabilities		(199)	(471)
Net deferred tax asset (liability)		$ (181)	$ (407)

[1] Related to National Interstate Corporation, a 51%-owned subsidiary.