Acquisitions and Sale of Businesses (Details) - USD ($) $ in Millions			9 Months Ended
		Apr. 01, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Business Acquisition [Line Items]
Total purchase price			$ 0	$ 267
Allocation of excess purchase price:
Goodwill			$ 201		$ 201
Summit Holding Southeast, Inc [Member]
Business Acquisition [Line Items]
Total purchase price		$ 259
Tangible assets acquired:
Cash and cash equivalents		1,078
Fixed maturities, available for sale		92
Recoverables from reinsurers		116
Agents’ balances and premiums receivable		41
Deferred tax assets, net	[1]	67
Other receivables		21
Other assets		11
Total tangible assets acquired		1,426
Liabilities acquired:
Unpaid losses and loss adjustment expenses		1,142
Unearned premiums		3
Payable to reinsurers		3
Other liabilities		66
Total liabilities acquired		1,214
Net tangible assets acquired, at fair value		212
Excess purchase price over net tangible assets acquired		47
Allocation of excess purchase price:
Intangible assets acquired	[2]	47
Deferred tax on intangible assets acquired	[1]	(16)
Goodwill		$ 16

[1] AFG’s net deferred tax assets are included in Other assets in AFG’s Consolidated Balance Sheet at September 30, 2015.

[2] Included in Other assets in AFG’s Consolidated Balance Sheet.