Condensed Financial Information of Parent Company - Condensed Statement of Earnings (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Revenues:
Total revenues	$ 2,623	$ 2,060	$ 1,951	$ 1,275	$ 2,130	$ 2,123	$ 1,960	$ 2,024	$ 7,909	$ 8,237	$ 7,150
Costs and Expenses:
Interest charges on other borrowings									88	68	62
Other expenses									430	441	393
Total costs and expenses									7,061	7,129	6,511
Earnings before income taxes									848	1,108	639
Provision for income taxes									127	239	122
Net Earnings Attributable to Shareholders	$ 692	$ 164	$ 177	$ (301)	$ 211	$ 147	$ 210	$ 329	732	897	530
AFG
Revenues:
Dividends from subsidiaries									543	417	261
Equity in undistributed earnings of subsidiaries									474	888	529
Investment and other income									32	20	2
Total revenues									1,049	1,325	792
Costs and Expenses:
Interest charges on intercompany borrowings									8	8	8
Interest charges on other borrowings									88	68	62
Other expenses									94	113	70
Total costs and expenses									190	189	140
Earnings before income taxes									859	1,136	652
Provision for income taxes									127	239	122
Net Earnings Attributable to Shareholders									$ 732	$ 897	$ 530