Condensed Financial Information of Parent Company - Condensed Statement of Comprehensive Income (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
Statement of Other Comprehensive Income [Abstract]
Net earnings (losses) attributable to shareholders	$ (29)	$ 204	$ 210	$ 145	$ 166	$ 11	$ 145	$ 153	$ 530	$ 475	$ 649
Comprehensive income (loss) attributable to shareholders									(14)	771	711
AFG
Statement of Other Comprehensive Income [Abstract]
Net earnings (losses) attributable to shareholders									530	475	649
Other comprehensive income (loss), net of tax									(544)	296	62
Comprehensive income (loss) attributable to shareholders									$ (14)	$ 771	$ 711