Condensed Financial Information of Parent Company - Condensed Statement of Earnings (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Revenues:
Total revenues	$ 1,690	$ 2,008	$ 1,833	$ 1,619	$ 1,808	$ 1,835	$ 1,646	$ 1,576	$ 7,150	$ 6,865	$ 6,498
Costs and Expenses:
Interest charges on other borrowings									62	85	77
Other expenses									353	422	353
Total costs and expenses									6,511	6,141	5,711
Earnings before income taxes									639	724	787
Provision for income taxes									122	247	119
Net Earnings Attributable to Shareholders	$ (29)	$ 204	$ 210	$ 145	166	$ 11	$ 145	$ 153	530	475	649
AFG
Revenues:
Dividends from subsidiaries									261	681	643
Equity in undistributed earnings of subsidiaries									529	264	286
Investment and other income									2	13	7
Total revenues									792	958	936
Costs and Expenses:
Interest charges on intercompany borrowings									8	9	9
Interest charges on other borrowings									62	85	77
Other expenses									70	142	82
Total costs and expenses									140	236	168
Earnings before income taxes									652	722	768
Provision for income taxes					$ (56)				122	247	119
Net Earnings Attributable to Shareholders									$ 530	$ 475	$ 649