Condensed Financial Information of Parent Company - Condensed Statement of Cash Flows (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Operating Activities:
Net earnings attributable to shareholders	$ 385	$ 109	$ 54	$ 101	$ 129	$ 63	$ 141	$ 19	$ 649	$ 352	$ 452
Adjustments:
Net cash provided by operating activities									1,150	1,353	1,231
Investing Activities:
Net cash used in investing activities									(2,981)	(4,573)	(3,628)
Financing Activities:
Additional long-term borrowings									302	145	145
Reductions of long-term debt									(18)	(192)	(2)
Issuances of Common Stock									35	61	47
Repurchases of Common Stock									(133)	(126)	(191)
Cash dividends paid on Common Stock									(185)	(176)	(167)
Net cash provided by (used in) financing activities									2,718	3,097	2,101
Net Change in Cash and Cash Equivalents									887	(123)	(296)
Cash and cash equivalents at beginning of year				1,220				1,343	1,220	1,343	1,639
Cash and cash equivalents at end of year	2,107				1,220				2,107	1,220	1,343
AFG
Operating Activities:
Net earnings attributable to shareholders									649	352	452
Adjustments:
Equity in net earnings of subsidiaries									(638)	(451)	(545)
Dividends from subsidiaries									611	280	451
Other operating activities, net									(67)	(19)	14
Net cash provided by operating activities									555	162	372
Investing Activities:
Capital contributions to subsidiaries									(560)	(27)	(431)
Returns of capital from subsidiaries									0	1	0
Purchases of investments, property and equipment									(1)	(10)	(1)
Proceeds from maturities and redemptions of investments									1	0	0
Proceeds from sales of investments, property and equipment									0	3	0
Net cash used in investing activities									(560)	(33)	(432)
Financing Activities:
Additional long-term borrowings									296	145	145
Reductions of long-term debt									0	(132)	0
Issuances of Common Stock									35	57	42
Repurchases of Common Stock									(133)	(126)	(191)
Cash dividends paid on Common Stock									(185)	(176)	(167)
Net cash provided by (used in) financing activities									13	(232)	(171)
Net Change in Cash and Cash Equivalents									8	(103)	(231)
Cash and cash equivalents at beginning of year				$ 189				$ 292	189	292	523
Cash and cash equivalents at end of year	$ 197				$ 189				$ 197	$ 189	$ 292