Income Taxes - Significant components of deferred tax assets and liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Deferred tax assets:
Federal net operating loss carryforwards	$ 50	$ 50
Foreign underwriting losses	120	77
Capital loss carryforwards	83	32
Insurance claims and reserves	801	713
Employee benefits	131	115
Other, net	35	29
Total deferred tax assets before valuation allowance	1,220	1,016
Valuation allowance against deferred tax assets	(173)	(130)
Total deferred tax assets	1,047	886
Deferred tax liabilities:
Subsidiaries not in AFG’s tax return	0	(63)
Investment securities	(307)	(258)
Deferred policy acquisition costs	(352)	(336)
Total deferred tax liabilities	(659)	(657)
Net deferred tax asset (liability)	388	229
Excluding Unrealized Gains
Deferred tax assets:
Federal net operating loss carryforwards	50	50
Foreign underwriting losses	120	77
Capital loss carryforwards	83	32
Insurance claims and reserves	774	691
Employee benefits	131	115
Other, net	40	33
Total deferred tax assets before valuation allowance	1,198	998
Valuation allowance against deferred tax assets	(173)	(130)
Total deferred tax assets	1,025	868
Deferred tax liabilities:
Subsidiaries not in AFG’s tax return	0	(63)
Investment securities	29	23
Deferred policy acquisition costs	(448)	(418)
Total deferred tax liabilities	(419)	(458)
Net deferred tax asset (liability)	606	410
Impact of Unrealized Gains
Deferred tax assets:
Federal net operating loss carryforwards	0	0
Foreign underwriting losses	0	0
Capital loss carryforwards	0	0
Insurance claims and reserves	27	22
Employee benefits	0	0
Other, net	(5)	(4)
Total deferred tax assets before valuation allowance	22	18
Valuation allowance against deferred tax assets	0	0
Total deferred tax assets	22	18
Deferred tax liabilities:
Subsidiaries not in AFG’s tax return	0	0
Investment securities	(336)	(281)
Deferred policy acquisition costs	96	82
Total deferred tax liabilities	(240)	(199)
Net deferred tax asset (liability)	$ (218)	$ (181)