Condensed Financial Information of Parent Company - Condensed Statement of Comprehensive Income (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
Statement of Other Comprehensive Income [Abstract]
Net earnings attributable to shareholders	$ 211	$ 147	$ 210	$ 329	$ (29)	$ 204	$ 210	$ 145	$ 897	$ 530	$ 475
Comprehensive income (loss) attributable to shareholders									1,712	(14)	771
AFG
Statement of Other Comprehensive Income [Abstract]
Net earnings attributable to shareholders									897	530	475
Other comprehensive income (loss), net of tax									815	(544)	296
Comprehensive income (loss) attributable to shareholders									$ 1,712	$ (14)	$ 771