Condensed Financial Information of Parent Company - Condensed Statement of Comprehensive Income (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
Statement of Other Comprehensive Income [Abstract]
Net earnings (loss) attributable to shareholders	$ 692	$ 164	$ 177	$ (301)	$ 211	$ 147	$ 210	$ 329	$ 732	$ 897	$ 530
Comprehensive income (loss) attributable to shareholders									1,146	1,712	(14)
AFG
Statement of Other Comprehensive Income [Abstract]
Net earnings (loss) attributable to shareholders									732	897	530
Other comprehensive income (loss), net of tax									414	815	(544)
Comprehensive income (loss) attributable to shareholders									$ 1,146	$ 1,712	$ (14)