Consolidated Statement of Earnings - USD ($) shares in Millions, $ in Millions	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenues:
Property and casualty insurance net earned premiums	$ 4,579	$ 4,328	$ 4,224
Life, accident and health net earned premiums	22	24	104
Net investment income	1,831	1,696	1,633
Realized gains (losses) on:
Securities	5	19	(19)
Subsidiaries	0	2	(161)
Income (loss) of managed investment entities:
Investment income	210	190	155
Gain (loss) on change in fair value of assets/liabilities	12	15	(34)
Other income	206	224	243
Total revenues	6,865	6,498	6,145
Costs and Expenses:
Property and casualty insurance: Losses and loss adjustment expenses	2,955	2,762	2,695
Property and casualty insurance: Commissions and other underwriting expenses	1,407	1,349	1,320
Annuity benefits	892	800	732
Life, accident and health benefits	26	33	131
Annuity and supplemental insurance acquisition expenses	173	186	179
Interest charges on borrowed money	85	77	75
Expenses of managed investment entities	181	151	112
Other expenses	422	353	336
Total costs and expenses	6,141	5,711	5,580
Earnings before income taxes	724	787	565
Provision for income taxes	247	119	195
Net earnings, including noncontrolling interests	477	668	370
Less: Net earnings attributable to noncontrolling interests	2	19	18
Net Earnings Attributable to Shareholders	$ 475	$ 649	$ 352
Earnings Attributable to Shareholders per Common Share:
Basic (USD per share)	$ 5.40	$ 7.47	$ 4.02
Diluted (USD per share)	$ 5.28	$ 7.33	$ 3.94
Average number of Common Shares:
Basic (shares)	87.8	86.9	87.6
Diluted (shares)	89.8	88.5	89.4
Cash dividends per Common Share (USD per share)	$ 4.7875	$ 2.1525	$ 2.03
Supplemental disclosure of Realized gains (losses) on securities:
Realized gains before impairments	$ 78	$ 135	$ 106
Losses on securities with impairment	(74)	(115)	(125)
Non-credit portion recognized in other comprehensive income (loss)	1	(1)	0
Impairment charges recognized in earnings	(73)	(116)	(125)
Total realized gains (losses) on securities	$ 5	$ 19	$ (19)

Annuity and supplemental insurance acquisition expenses.

No definition available.

Name:	afg_AnnuityAndSupplementalInsuranceAcquisitionExpenses
Namespace Prefix:	afg_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Annuity benefits includes 1) interest credited to policyholders accounts, which provides a guaranteed yield, 2) expenses related to excess benefits expected to be paid on future deaths and annuitizations and 3) net expenses related to changes in embedded derivatives on equity indexed annuities offset by equity index call options.

+ References

No definition available.