Condensed Financial Information of Parent Company - Condensed Statement of Earnings (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Revenues:
Total revenues	$ 2,130	$ 2,123	$ 1,960	$ 2,024	$ 1,690	$ 2,008	$ 1,833	$ 1,619	$ 8,237	$ 7,150	$ 6,865
Costs and Expenses:
Interest charges on other borrowings									68	62	85
Other expenses									405	353	422
Total costs and expenses									7,129	6,511	6,141
Earnings before income taxes									1,108	639	724
Provision for income taxes									239	122	247
Net Earnings Attributable to Shareholders	$ 211	$ 147	$ 210	$ 329	$ (29)	$ 204	$ 210	$ 145	897	530	475
AFG
Revenues:
Dividends from subsidiaries									417	261	681
Equity in undistributed earnings of subsidiaries									888	529	264
Investment and other income									20	2	13
Total revenues									1,325	792	958
Costs and Expenses:
Interest charges on intercompany borrowings									8	8	9
Interest charges on other borrowings									68	62	85
Other expenses									113	70	142
Total costs and expenses									189	140	236
Earnings before income taxes									1,136	652	722
Provision for income taxes									239	122	247
Net Earnings Attributable to Shareholders									$ 897	$ 530	$ 475