American Financial (AFG) 10-K 23 Feb 18 2017 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Feb. 01, 2018	Jun. 30, 2017
Document and Entity Information [Abstract]
Entity Registrant Name	AMERICAN FINANCIAL GROUP INC
Entity Central Index Key	1,042,046
Document Type	10-K
Document Period End Date	Dec. 31, 2017
Amendment Flag	false
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	FY
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Large Accelerated Filer
Entity Public Float			$ 7,640
Entity Common Stock, Shares Outstanding		88,425,972

Consolidated Balance Sheet

Consolidated Balance Sheet - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Assets:
Cash and cash equivalents	$ 2,338	$ 2,107
Investments:
Fixed maturities, available for sale at fair value (amortized cost — $37,038 and $33,735)	38,379	34,544
Fixed maturities, trading at fair value	348	359
Equity securities, available for sale at fair value (cost — $1,321 and $1,351)	1,600	1,502
Equity securities, trading at fair value	62	56
Mortgage loans	1,125	1,147
Policy loans	184	192
Equity index call options	701	492
Real estate and other investments	1,311	1,034
Total cash and investments	46,048	41,433
Recoverables from reinsurers	3,369	2,737
Prepaid reinsurance premiums	600	539
Agents’ balances and premiums receivable	1,146	997
Deferred policy acquisition costs	1,216	1,239
Assets of managed investment entities	4,902	4,765
Other receivables	1,030	908
Variable annuity assets (separate accounts)	644	600
Other assets	1,504	1,655
Goodwill	199	199
Total assets	60,658	55,072
Liabilities and Equity:
Unpaid losses and loss adjustment expenses	9,678	8,563
Unearned premiums	2,410	2,171
Annuity benefits accumulated	33,316	29,907
Life, accident and health reserves	658	691
Payable to reinsurers	743	634
Liabilities of managed investment entities	4,687	4,549
Long-term debt	1,301	1,283
Variable annuity liabilities (separate accounts)	644	600
Other liabilities	1,887	1,755
Total liabilities	55,324	50,153
Temporary equity
Redeemable noncontrolling interests	3	0
Shareholders’ equity:
Common Stock, no par value — 200,000,000 shares authorized — 88,275,460 and 86,924,399 shares outstanding	88	87
Capital surplus	1,181	1,111
Retained earnings	3,248	3,343
Accumulated other comprehensive income, net of tax	813	375
Total shareholders’ equity	5,330	4,916
Noncontrolling interests	1	3
Total equity	5,331	4,919
Total liabilities and equity	$ 60,658	$ 55,072

Consolidated Balance Sheet (Par

Consolidated Balance Sheet (Parenthetical) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Statement of Financial Position [Abstract]
Fixed maturities, available for sale at amortized cost	$ 37,038	$ 33,735
Equity securities, available for sale at cost	$ 1,321	$ 1,351
Common Stock, par value (USD per share)	$ 0	$ 0
Common Stock, shares authorized	200,000,000	200,000,000
Common Stock, shares outstanding	88,275,460	86,924,399

Consolidated Statement of Earni

Consolidated Statement of Earnings - USD ($) shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenues:
Property and casualty insurance net earned premiums	$ 4,579	$ 4,328	$ 4,224
Life, accident and health net earned premiums	22	24	104
Net investment income	1,831	1,696	1,633
Realized gains (losses) on:
Securities	5	19	(19)
Subsidiaries	0	2	(161)
Income (loss) of managed investment entities:
Investment income	210	190	155
Gain (loss) on change in fair value of assets/liabilities	12	15	(34)
Other income	206	224	243
Total revenues	6,865	6,498	6,145
Costs and Expenses:
Property and casualty insurance: Losses and loss adjustment expenses	2,955	2,762	2,695
Property and casualty insurance: Commissions and other underwriting expenses	1,407	1,349	1,320
Annuity benefits	892	800	732
Life, accident and health benefits	26	33	131
Annuity and supplemental insurance acquisition expenses	173	186	179
Interest charges on borrowed money	85	77	75
Expenses of managed investment entities	181	151	112
Other expenses	422	353	336
Total costs and expenses	6,141	5,711	5,580
Earnings before income taxes	724	787	565
Provision for income taxes	247	119	195
Net earnings, including noncontrolling interests	477	668	370
Less: Net earnings attributable to noncontrolling interests	2	19	18
Net Earnings Attributable to Shareholders	$ 475	$ 649	$ 352
Earnings Attributable to Shareholders per Common Share:
Basic (USD per share)	$ 5.40	$ 7.47	$ 4.02
Diluted (USD per share)	$ 5.28	$ 7.33	$ 3.94
Average number of Common Shares:
Basic (shares)	87.8	86.9	87.6
Diluted (shares)	89.8	88.5	89.4
Cash dividends per Common Share (USD per share)	$ 4.7875	$ 2.1525	$ 2.03
Supplemental disclosure of Realized gains (losses) on securities:
Realized gains before impairments	$ 78	$ 135	$ 106
Losses on securities with impairment	(74)	(115)	(125)
Non-credit portion recognized in other comprehensive income (loss)	1	(1)	0
Impairment charges recognized in earnings	(73)	(116)	(125)
Total realized gains (losses) on securities	$ 5	$ 19	$ (19)

Consolidated Statement of Compr

Consolidated Statement of Comprehensive Income - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement of Comprehensive Income [Abstract]
Net earnings, including noncontrolling interests	$ 477	$ 668	$ 370
Net unrealized gains (losses) on securities:
Unrealized holding gains (losses) on securities arising during the period	297	80	(406)
Reclassification adjustment for realized (gains) losses included in net earnings	(10)	(12)	9
Reclassification for unrealized gains of subsidiaries sold	0	0	(22)
Total net unrealized gains (losses) on securities	287	68	(419)
Net unrealized gains (losses) on cash flow hedges	(4)	(8)	1
Foreign currency translation adjustments	12	7	(14)
Pension and other postretirement plans adjustments	1	0	1
Other comprehensive income (loss), net of tax	296	67	(431)
Total comprehensive income (loss), net of tax	773	735	(61)
Less: Comprehensive income attributable to noncontrolling interests	2	24	10
Comprehensive income (loss) attributable to shareholders	$ 771	$ 711	$ (71)

Consolidated Statement of Chang

Consolidated Statement of Changes in Equity - USD ($) $ in Millions	Total	Total	Common Shares	Common Stock and Capital Surplus	Retained Earnings	Accumulated Other Comprehensive Inc. (Loss)		Noncontrolling Interests
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect of accounting change	$ 2	$ 2			$ 2
Beginning Balance, shares at Dec. 31, 2014			87,708,793
Beginning Balance at Dec. 31, 2014	5,054	4,879		$ 1,240	2,912	$ 727		$ 175
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net earnings	370	352			352			18
Other comprehensive income (loss)	(431)	(423)				(423)		(8)
Dividends on Common Stock	(178)	(178)			(178)
Shares issued:
Exercise of stock options, shares			1,475,202
Exercise of stock options	47	47		47
Restricted stock awards, shares			171,130
Restricted stock awards	0	0		0
Other benefit plans, shares			111,681
Other benefit plans	7	7		7
Dividend reinvestment plan, shares			26,167
Dividend reinvestment plan	2	2		2
Stock-based compensation:
Stock-based compensation: Expense	21	21		21
Stock-based compensation: Excess tax benefits	12	12		12
Shares acquired and retired, shares			(1,955,186)
Shares acquired and retired	(126)	(126)		(27)	(99)
Shares exchanged — benefit plans, shares			(45,765)
Shares exchanged — benefit plans	(3)	(3)		(1)	(2)
Forfeitures of restricted stock, shares			(17,570)
Forfeitures of restricted stock	0	0		0
Other	(7)				0			(7)
Ending Balance, shares at Dec. 31, 2015			87,474,452
Ending Balance at Dec. 31, 2015	4,770	4,592		1,301	2,987	304		178
Beginning Balance, Redeemable Noncontrolling Interests at Dec. 31, 2014	0
Ending Balance, Redeemable Noncontrolling Interests at Dec. 31, 2015	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net earnings	668	649			649			19
Other comprehensive income (loss)	67	62				62		5
Dividends on Common Stock	(187)	(187)			(187)
Shares issued:
Exercise of stock options, shares			958,344
Exercise of stock options	32	32		32
Restricted stock awards, shares			318,940
Restricted stock awards	0	0		0
Other benefit plans, shares			95,875
Other benefit plans	7	7		7
Dividend reinvestment plan, shares			25,516
Dividend reinvestment plan	2	2		2
Stock-based compensation:
Stock-based compensation: Expense	22	22		22
Shares acquired and retired, shares			(1,911,976)
Shares acquired and retired	(133)	(133)		(29)	(104)
Shares exchanged — benefit plans, shares			(32,707)
Shares exchanged — benefit plans	(2)	(2)		0	(2)
Forfeitures of restricted stock, shares			(4,045)
Forfeitures of restricted stock	0	0		0
Acquisition of noncontrolling interests	(315)	(128)		(137)		9	[1]	(187)
Other	$ (12)	0			0	0		(12)
Ending Balance, shares at Dec. 31, 2016	86,924,399		86,924,399
Ending Balance at Dec. 31, 2016	$ 4,919	4,916		1,198	3,343	375		3
Ending Balance, Redeemable Noncontrolling Interests at Dec. 31, 2016	0
Redeemable Noncontrolling Interest, Equity, Carrying Amount [Abstract]
Redeemable noncontrolling interests	0
Net earnings	477	475			475			2
Other comprehensive income (loss)	296	296				296		0
Dividends on Common Stock	$ (421)	(421)			(421)
Exercise of stock options, shares	1,020,986		1,020,986
Exercise of stock options	$ 34	34		34
Restricted stock awards, shares			232,250
Restricted stock awards	0	0		0
Other benefit plans, shares			99,588
Other benefit plans	10	10		10
Dividend reinvestment plan, shares			42,572
Dividend reinvestment plan	4	4		4
Stock-based compensation: Expense	24	24		24
Shares exchanged — benefit plans, shares			(37,718)
Shares exchanged — benefit plans	(5)	(5)		(1)	(4)
Forfeitures of restricted stock, shares			(6,617)
Forfeitures of restricted stock	0	0		0
Sale of redeemable noncontrolling interests	(3)	(3)				(3)		0
Other	$ (4)							(4)
Ending Balance, shares at Dec. 31, 2017	88,275,460		88,275,460
Ending Balance at Dec. 31, 2017	$ 5,331	5,330		$ 1,269	3,248	813		1
Ending Balance, Redeemable Noncontrolling Interests at Dec. 31, 2017	3
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect of accounting change	0	$ 0			$ (145)	$ 145		$ 0
Redeemable Noncontrolling Interest, Equity, Carrying Amount [Abstract]
Redeemable noncontrolling interests	$ 3
[1]	Other includes the December 2017 reclassification of $145 million stranded in AOCI from accounting for the Tax Cuts and Jobs Act of 2017 to retained earnings (see Note A — “Accounting Policies — Income Taxes”), and the impact on AOCI of the December 2017 sale of redeemable noncontrolling interests in Neon and the November 2016 acquisition of the noncontrolling interest in NATL (see Note B — “Acquisitions and Sale of Businesses”).

Consolidated Statement of Cash

Consolidated Statement of Cash Flows - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Operating Activities:
Net earnings, including noncontrolling interests	$ 477	$ 668	$ 370
Adjustments:
Depreciation and amortization	107	134	134
Annuity benefits	892	800	732
Realized (gains) losses on investing activities	(23)	(61)	100
Net sales of trading securities	17	79	10
Deferred annuity and life policy acquisition costs	(225)	(230)	(224)
Change in:
Reinsurance and other receivables	(963)	(315)	(10)
Other assets	13	(467)	(13)
Insurance claims and reserves	1,321	533	451
Payable to reinsurers	109	43	(54)
Other liabilities	(18)	265	12
Managed investment entities’ assets/liabilities	60	(279)	(190)
Other operating activities, net	37	(20)	35
Net cash provided by operating activities	1,804	1,150	1,353
Investing Activities:
Purchases of fixed maturities	(9,485)	(7,537)	(7,201)
Purchases of equity securities	(182)	(207)	(570)
Purchases of mortgage loans	(254)	(341)	(213)
Purchases of equity index call options and other investments	(831)	(738)	(534)
Purchases of real estate, property and equipment	(109)	(49)	(102)
Proceeds from maturities and redemptions of fixed maturities	6,105	4,713	3,333
Proceeds from repayments of mortgage loans	215	262	265
Proceeds from sales of fixed maturities	392	641	321
Proceeds from sales of equity securities	216	348	364
Proceeds from sales and settlements of equity index call options and other investments	789	319	374
Proceeds from sales of real estate, property and equipment	55	55	117
Proceeds from sales of businesses	0	0	7
Cash and cash equivalents of businesses sold	0	0	(49)
Managed investment entities:
Purchases of investments	(2,979)	(2,254)	(1,530)
Proceeds from sales and redemptions of investments	2,774	1,890	855
Other investing activities, net	2	(83)	(10)
Net cash used in investing activities	(3,292)	(2,981)	(4,573)
Financing Activities:
Annuity receipts	4,341	4,585	4,485
Annuity surrenders, benefits and withdrawals	(2,405)	(2,275)	(2,025)
Net transfers from variable annuity assets	54	42	43
Additional long-term borrowings	712	302	145
Reductions of long-term debt	(745)	(18)	(192)
Issuances of managed investment entities’ liabilities	2,731	2,293	1,026
Retirements of managed investment entities’ liabilities	(2,585)	(1,600)	(136)
Issuances of Common Stock	37	35	61
Repurchases of Common Stock	0	(133)	(126)
Cash dividends paid on Common Stock	(417)	(185)	(176)
Acquisition of noncontrolling interests in subsidiary	0	(315)	0
Other financing activities, net	(4)	(13)	(8)
Net cash provided by (used in) financing activities	1,719	2,718	3,097
Net Change in Cash and Cash Equivalents	231	887	(123)
Cash and cash equivalents at beginning of year	2,107	1,220	1,343
Cash and cash equivalents at end of year	$ 2,338	$ 2,107	$ 1,220

Accounting Policies

Accounting Policies	12 Months Ended
	Dec. 31, 2017
Accounting Policies [Abstract]
Accounting Policies	Accounting Policies Basis of Presentation The consolidated financial statements include the accounts of American Financial Group, Inc. and its subsidiaries (“AFG”). Certain reclassifications have been made to prior years to conform to the current year’s presentation. All significant intercompany balances and transactions have been eliminated. The results of operations of companies since their formation or acquisition are included in the consolidated financial statements. Events or transactions occurring subsequent to December 31, 2017 , and prior to the filing of this Form 10-K, have been evaluated for potential recognition or disclosure herein. The preparation of the financial statements in conformity with U.S. generally accepted accounting principles (“GAAP”) requires management to make estimates and assumptions that affect the amounts reported in the financial statements and accompanying notes. Changes in circumstances could cause actual results to differ materially from those estimates. Fair Value Measurements Accounting standards define fair value as the price that would be received to sell an asset or paid to transfer a liability (an exit price) in an orderly transaction between market participants on the measurement date. The standards establish a hierarchy of valuation techniques based on whether the assumptions that market participants would use in pricing the asset or liability (“inputs”) are observable or unobservable. Observable inputs reflect market data obtained from independent sources, while unobservable inputs reflect AFG’s assumptions about the assumptions market participants would use in pricing the asset or liability. AFG did not have any significant nonrecurring fair value measurements of nonfinancial assets and liabilities in 2017 or 2016 . Investments Fixed maturity and equity securities classified as “available for sale” are reported at fair value with unrealized gains and losses included in accumulated other comprehensive income (“AOCI”) in AFG’s Balance Sheet. Fixed maturity and equity securities classified as “trading” are reported at fair value with changes in unrealized holding gains or losses during the period included in net investment income. Mortgage and policy loans are carried primarily at the aggregate unpaid balance. In January 2016, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2016-01, which, among other things, will require all equity securities currently classified as “available for sale” to be reported at fair value, with holding gains and losses recognized in net earnings, instead of AOCI. AFG will be required to adopt this guidance effective January 1, 2018. At the date of adoption, the $221 million net unrealized gain on equity securities included in AOCI as of December 31, 2017 will be reclassified to retained earnings as the cumulative effect of an accounting change. Premiums and discounts on fixed maturity securities are amortized using the effective interest method. Mortgage-backed securities (“MBS”) are amortized over a period based on estimated future principal payments, including prepayments. Prepayment assumptions are reviewed periodically and adjusted to reflect actual prepayments and changes in expectations. Gains or losses on securities are determined on the specific identification basis. When a decline in the value of a specific investment is considered to be other-than-temporary at the balance sheet date, a provision for impairment is charged to earnings (included in realized gains (losses) on securities) and the cost basis of that investment is reduced. If management can assert that it does not intend to sell an impaired fixed maturity security and it is not more likely than not that it will have to sell the security before recovery of its amortized cost basis, then the other-than-temporary impairment is separated into two components: (i) the amount related to credit losses (recorded in earnings) and (ii) the amount related to all other factors (recorded in other comprehensive income). The credit-related portion of an other-than-temporary impairment is measured by comparing a security’s amortized cost to the present value of its current expected cash flows discounted at its effective yield prior to the impairment charge. Both components are shown in the statement of earnings. If management intends to sell an impaired security, or it is more likely than not that it will be required to sell the security before recovery, an impairment charge to earnings is recorded to reduce the amortized cost of that security to fair value. Derivatives Derivatives included in AFG’s Balance Sheet are recorded at fair value. Changes in fair value of derivatives are included in earnings, unless the derivatives are designated and qualify as highly effective cash flow hedges. Derivatives that do not qualify for hedge accounting under GAAP consist primarily of (i) components of certain fixed maturity securities (primarily interest-only MBS) and (ii) the equity-based component of certain annuity products (included in annuity benefits accumulated) and related equity index call options designed to be consistent with the characteristics of the liabilities and used to mitigate the risk embedded in those annuity products. To qualify for hedge accounting, at the inception of a derivative contract, AFG formally documents the relationship between the terms of the hedge and the hedged items and its risk management objective. This documentation includes defining how hedge effectiveness and ineffectiveness will be measured on a retrospective and prospective basis. Changes in the fair value of derivatives that are designated and qualify as highly effective cash flow hedges are recorded in AOCI and are reclassified into earnings when the variability of the cash flows from the hedged items impacts earnings. Any hedge ineffectiveness is immediately recorded in current period earnings. When the change in the fair value of a qualifying cash flow hedge is included in earnings, it is included in the same line item in the statement of earnings as the cash flows from the hedged item. AFG uses interest rate swaps that are designated and qualify as highly effective cash flow hedges to mitigate interest rate risk related to certain floating-rate securities included in AFG’s portfolio of fixed maturity securities. For derivatives that are designated and qualify as highly effective fair value hedges, changes in the fair value of the derivative, along with changes in the fair value of the hedged item attributable to the hedged risk, are recognized in current period earnings. Goodwill Goodwill represents the excess of cost of subsidiaries over AFG’s equity in their underlying net assets. Goodwill is not amortized, but is subject to an impairment test at least annually. An entity is not required to complete the quantitative annual goodwill impairment test on a reporting unit if the entity elects to perform a qualitative analysis and determines that it is more likely than not that the reporting unit’s fair value exceeds its carrying amount. Reinsurance Amounts recoverable from reinsurers are estimated in a manner consistent with the claim liability associated with the reinsured policies. AFG’s property and casualty insurance subsidiaries report as assets (i) the estimated reinsurance recoverable on paid and unpaid losses, including an estimate for losses incurred but not reported, and (ii) amounts paid or due to reinsurers applicable to the unexpired terms of policies in force. Payable to reinsurers includes ceded premiums due to reinsurers, as well as ceded premiums retained by AFG’s property and casualty insurance subsidiaries under contracts to fund ceded losses as they become due. AFG’s insurance subsidiaries also assume reinsurance from other companies. Earnings on reinsurance assumed is recognized based on information received from ceding companies. An AFG subsidiary cedes life insurance policies to a third party on a funds withheld basis whereby the subsidiary retains the assets (securities) associated with the reinsurance contract. Interest is credited to the reinsurer based on the actual investment performance of the retained assets. This reinsurance contract is considered to contain an embedded derivative (that must be adjusted to fair value) because the yield on the payable is based on a specific block of the ceding company’s assets, rather than the overall creditworthiness of the ceding company. AFG determined that changes in the fair value of the underlying portfolio of fixed maturity securities is an appropriate measure of the value of the embedded derivative. The securities related to this contract are classified as “trading.” The adjustment to fair value on the embedded derivative offsets the investment income recorded on the adjustment to fair value of the related trading portfolio. Deferred Policy Acquisition Costs (“DPAC”) Policy acquisition costs (principally commissions, premium taxes and certain underwriting and policy issuance costs) directly related to the successful acquisition or renewal of an insurance contract are deferred. DPAC also includes capitalized costs associated with sales inducements offered to fixed annuity policyholders such as enhanced interest rates and premium and persistency bonuses. For the property and casualty companies, DPAC is limited based upon recoverability without any consideration for anticipated investment income and is charged against income ratably over the terms of the related policies. A premium deficiency is recognized if the sum of expected claims costs, claims adjustment expenses and unamortized acquisition costs exceed the related unearned premiums. A premium deficiency is first recognized by charging any unamortized acquisition costs to expense to the extent required to eliminate the deficiency. If the premium deficiency is greater than unamortized acquisition costs, a liability is accrued for the excess deficiency and reported with unpaid losses and loss adjustment expenses. DPAC related to annuities is deferred to the extent deemed recoverable and amortized, with interest, in relation to the present value of actual and expected gross profits on the policies. Expected gross profits consist principally of estimated future investment margin (estimated future net investment income less interest credited on policyholder funds) and surrender, mortality, and other life and annuity policy charges, less death, annuitization and guaranteed withdrawal benefits in excess of account balances and estimated future policy administration expenses. To the extent that realized gains and losses result in adjustments to the amortization of DPAC related to annuities, such adjustments are reflected as components of realized gains (losses) on securities. DPAC related to traditional life and health insurance is amortized over the expected premium paying period of the related policies, in proportion to the ratio of annual premium revenues to total anticipated premium revenues. See “ Life, Accident and Health Reserves ” below for details on the impact of loss recognition on the accounting for traditional life and health insurance contracts. DPAC includes the present value of future profits on business in force of annuity and life, accident and health insurance companies acquired (“PVFP”). PVFP represents the portion of the costs to acquire companies that is allocated to the value of the right to receive future cash flows from insurance contracts existing at the date of acquisition. PVFP is amortized with interest in relation to expected gross profits of the acquired policies for annuities and universal life products and in relation to the premium paying period for traditional life and health insurance products. DPAC and certain other balance sheet amounts related to annuity, long-term care and life businesses are also adjusted, net of tax, for the change in expense that would have been recorded if the unrealized gains (losses) from securities had actually been realized. These adjustments are included in unrealized gains (losses) on marketable securities, a component of AOCI in AFG’s Balance Sheet. Managed Investment Entities A company is considered the primary beneficiary of, and therefore must consolidate, a variable interest entity (“VIE”) based primarily on its ability to direct the activities of the VIE that most significantly impact that entity’s economic performance and the obligation to absorb losses of, or receive benefits from, the entity that could potentially be significant to the VIE. AFG manages, and has investments in, collateralized loan obligations (“CLOs”) that are VIEs (see Note H — “ Managed Investment Entities ” ). AFG has determined that it is the primary beneficiary of the CLOs because (i) its role as asset manager gives it the power to direct the activities that most significantly impact the economic performance of the CLOs and (ii) through its investment in the CLO debt tranches, it has exposure to CLO losses (limited to the amount AFG invested) and the right to receive CLO benefits that could potentially be significant to the CLOs. On January 1, 2016, AFG adopted ASU 2015-02, which amended certain consolidation accounting guidance, including the VIE guidance that applies to collateralized financing entities such as CLOs. The new guidance affects how fee arrangements with CLO asset managers impact the determination of the primary beneficiary of those entities. Due to the significance of AFG’s investments in the CLOs that it manages, the new guidance did not impact the consolidation of AFG’s currently outstanding CLOs. The new guidance also impacted the consolidation analysis that applies to limited partnerships and similar entities, but did not result in a change to the accounting for AFG’s existing investments in those entities. Because AFG has no right to use the CLO assets and no obligation to pay the CLO liabilities, the assets and liabilities of the CLOs are shown separately in AFG’s Balance Sheet. AFG has elected the fair value option for reporting on the CLO assets and liabilities to improve the transparency of financial reporting related to the CLOs. The net gain or loss from accounting for the CLO assets and liabilities at fair value is presented separately in AFG’s Statement of Earnings. The fair values of a CLO’s assets may differ from the separately measured fair values of its liabilities even though the CLO liabilities only have recourse to the CLO assets. AFG has set the carrying value of the CLO liabilities equal to the fair value of the CLO assets (which have more observable fair values) as an alternative to reporting those liabilities at a separately measured fair value. CLO earnings attributable to AFG’s shareholders are measured by the change in the fair value of AFG’s investments in the CLOs and management fees earned. Prior to the adoption of new guidance effective January 1, 2015, measuring both the CLO assets and CLO liabilities at separately determined fair values resulted in a difference between the carrying value of the CLO assets and the carrying value of the CLO liabilities that was not attributable to AFG’s ownership interest in the CLOs. This difference was recorded as “appropriated retained earnings — managed investment entities” in AFG’s Balance Sheet. In accordance with the guidance adopted in 2015, the amount reported as “appropriated retained earnings — managed investment entities” at December 31, 2014 was reclassified to “liabilities of managed investment entities” on January 1, 2015 as the cumulative effect of an accounting change. Unpaid Losses and Loss Adjustment Expenses The net liabilities stated for unpaid claims and for expenses of investigation and adjustment of unpaid claims represent management’s best estimate and are based upon (i) the accumulation of case estimates for losses reported prior to the close of the accounting period on direct business written; (ii) estimates received from ceding reinsurers and insurance pools and associations; (iii) estimates of unreported losses (including possible development on known claims) based on past experience; (iv) estimates based on experience of expenses for investigating and adjusting claims; and (v) the current state of the law and coverage litigation. Establishing reserves for asbestos, environmental and other mass tort claims involves considerably more judgment than other types of claims due to, among other things, inconsistent court decisions, an increase in bankruptcy filings as a result of asbestos-related liabilities, novel theories of coverage, and judicial interpretations that often expand theories of recovery and broaden the scope of coverage. Loss reserve liabilities are subject to the impact of changes in claim amounts and frequency and other factors. Changes in estimates of the liabilities for losses and loss adjustment expenses are reflected in the statement of earnings in the period in which determined. Despite the variability inherent in such estimates, management believes that the liabilities for unpaid losses and loss adjustment expenses are adequate. Annuity Benefits Accumulated Annuity receipts and benefit payments are recorded as increases or decreases in annuity benefits accumulated rather than as revenue and expense. Increases in this liability for interest credited are charged to expense and decreases for policy charges are credited to other income. For certain products, annuity benefits accumulated also includes reserves for accrued persistency and premium bonuses, guaranteed withdrawals and excess benefits expected to be paid on future deaths and annuitizations (“EDAR”). The liabilities for EDAR and guaranteed withdrawals are accrued for and modified using assumptions consistent with those used in determining DPAC and DPAC amortization, except that amounts are determined in relation to the present value of total expected assessments. Total expected assessments consist principally of estimated future investment margin, surrender, mortality, and other life and annuity policy charges, and unearned revenues once they are recognized as income. Annuity benefits accumulated also includes amounts advanced from the Federal Home Loan Bank of Cincinnati. Unearned Revenue Certain upfront policy charges on annuities are deferred as unearned revenue (included in other liabilities) and recognized in net earnings (included in other income) using the same assumptions and estimated gross profits used to amortize DPAC. Life, Accident and Health Reserves Liabilities for future policy benefits under traditional life, accident and health policies are computed using the net level premium method. Computations are based on the original projections of investment yields, mortality, morbidity and surrenders and include provisions for unfavorable deviations unless a loss recognition event (premium deficiency) occurs. Claim reserves and liabilities established for accident and health claims are modified as necessary to reflect actual experience and developing trends. For long-duration contracts (such as traditional life and long-term care policies), loss recognition occurs when, based on current expectations as of the measurement date, existing contract liabilities plus the present value of future premiums (including reasonably expected rate increases) are not expected to cover the present value of future claims payments and related settlement and maintenance costs (excluding overhead) as well as unamortized acquisition costs. If a block of business is determined to be in loss recognition, a charge is recorded in earnings in an amount equal to the excess of the present value of expected future claims costs and unamortized acquisition costs over existing reserves plus the present value of expected future premiums (with no provision for adverse deviation). The charge is recorded first to reduce unamortized acquisition costs and then as an additional reserve (if unamortized acquisition costs have been reduced to zero). In addition, reserves for traditional life and long-term care policies are subject to adjustment for loss recognition charges that would have been recorded if the unrealized gains (losses) from securities had actually been realized. This adjustment is included in unrealized gains (losses) on marketable securities, a component of AOCI in AFG’s Balance Sheet. Debt Issuance Costs Debt issuance costs related to AFG’s outstanding debt are amortized over the life of the related debt using the effective interest method. Effective January 1, 2016, AFG adopted (on a retrospective basis) ASU 2015-03, which requires debt issuance costs to be presented in the balance sheet as a direct reduction in the carrying value of long-term debt (consistent with the treatment of debt discounts) with the periodic amortization of such costs included in interest expense. Debt issuance costs related to AFG’s revolving credit facilities will continue to be included in other assets in AFG’s Balance Sheet. Prior to AFG’s adoption of ASU 2015-03, AFG reported unamortized debt issuance costs as a deferred charge asset (included in other assets) in AFG’s Balance Sheet and the periodic amortization was included in other expenses in AFG’s Statement of Earnings. The updated guidance did not affect the overall recognition and measurement guidance for debt issuance costs. Accordingly, the guidance did not have an overall impact on AFG’s Shareholders’ Equity or results of operations. Variable Annuity Assets and Liabilities Separate accounts related to variable annuities represent the fair value of deposits invested in underlying investment funds on which AFG earns a fee. Investment funds are selected and may be changed only by the policyholder, who retains all investment risk. AFG’s variable annuity contracts contain a guaranteed minimum death benefit (“GMDB”) to be paid if the policyholder dies before the annuity payout period commences. In periods of declining equity markets, the GMDB may exceed the value of the policyholder’s account. A GMDB liability is established for future excess death benefits using assumptions together with a range of reasonably possible scenarios for investment fund performance that are consistent with DPAC capitalization and amortization assumptions. Premium Recognition Property and casualty premiums are earned generally over the terms of the policies on a pro rata basis. Unearned premiums represent that portion of premiums written, which is applicable to the unexpired terms of policies in force. On reinsurance assumed from other insurance companies or written through various underwriting organizations, unearned premiums are based on information received from such companies and organizations. For traditional life, accident and health products, premiums are recognized as revenue when legally collectible from policyholders. For interest-sensitive life and universal life products, premiums are recorded in a policyholder account, which is reflected as a liability. Revenue is recognized as amounts are assessed against the policyholder account for mortality coverage and contract expenses. Noncontrolling Interests For balance sheet purposes, noncontrolling interests represent the interests of shareholders other than AFG in consolidated entities. In the statement of earnings, net earnings and losses attributable to noncontrolling interests represents such shareholders’ interest in the earnings and losses of those entities. Noncontrolling interests that are redeemable at the option of the holder are presented separately in the mezzanine section of the balance sheet (between liabilities and equity). Income Taxes Deferred income taxes are calculated using the liability method. Under this method, deferred income tax assets and liabilities are determined based on differences between financial reporting and tax bases and are measured using enacted tax rates. A valuation allowance is established to reduce total deferred tax assets to an amount that will more likely than not be realized. AFG recognizes the tax benefits of uncertain tax positions only when the position is more likely than not to be sustained under examination by the appropriate taxing authority. Interest and penalties on AFG’s reserve for uncertain tax positions are recognized as a component of tax expense. The effect of a change in tax rates on deferred tax assets and liabilities is recorded in net earnings in the period that includes the enactment date. This includes the impact on deferred tax assets or liabilities established through AOCI, which results in an amount equal to the difference between the deferred tax at the historical corporate rate and the newly enacted rate stranded in AOCI. As permitted under guidance adopted effective December 31, 2017 (ASU 2018-02), AFG reclassified the $145 million stranded in AOCI from accounting for the Tax Cuts and Jobs Act of 2017 to retained earnings at December 31, 2017. See Note L — “ Income Taxes ” for further information. Stock-Based Compensation All share-based grants are recognized as compensation expense on a straight-line basis over their vesting periods based on their calculated fair value at the date of grant. AFG uses the Black-Scholes pricing model to measure the fair value of employee stock options. See Note K — “ Shareholders’ Equity ” for further information. In the fourth quarter of 2016, AFG early adopted ASU 2016-09, which, among other things, requires excess tax benefits or deficiencies for share-based payments to be recorded through income tax expense in the statement of earnings instead of directly to capital surplus (as required under the previous guidance). As a result, AFG’s Statement of Earnings includes a tax benefit of $17 million in 2017 and $9 million in 2016 that under the previous guidance would have been recorded directly to capital surplus. In addition, the new guidance allows entities to elect to account for forfeitures of awards when they occur rather than accruing expense based on an estimate of expected forfeitures (as required under the previous guidance). AFG has elected to account for forfeitures as they occur. The resulting cumulative effect of accounting change of less than $1 million was recorded directly to retained earnings on January 1, 2016. Benefit Plans AFG provides retirement benefits to qualified employees of participating companies through the AFG 401(k) Retirement and Savings Plan, a defined contribution plan. AFG makes all contributions to the retirement fund portion of the plan and matches a percentage of employee contributions to the savings fund. Company contributions are expensed in the year for which they are declared. AFG and many of its subsidiaries provide health care and life insurance benefits to eligible retirees. AFG also provides postemployment benefits to former or inactive employees (primarily those on disability) who were not deemed retired under other company plans. The projected future cost of providing these benefits is expensed over the period employees earn such benefits. Earnings Per Share Although basic earnings per share only considers shares of common stock outstanding during the period, the calculation of diluted earnings per share includes the following adjustments to weighted average common shares related to stock-based compensation plans: 2017 – 2.0 million , 2016 – 1.6 million and 2015 – 1.8 million . AFG’s weighted average diluted shares outstanding excludes the following anti-dilutive potential common shares related to stock compensation plans: 2017 – none , 2016 – 0.4 million and 2015 – 1.1 million . Adjustments to net earnings attributable to shareholders in the calculation of diluted earnings per share were nominal in the 2017 , 2016 and 2015 periods. Statement of Cash Flows For cash flow purposes, “investing activities” are defined as making and collecting loans and acquiring and disposing of debt or equity instruments and property and equipment. “Financing activities” include obtaining resources from owners and providing them with a return on their investments, borrowing money and repaying amounts borrowed. Annuity receipts, surrenders, benefits and withdrawals are also reflected as financing activities. All other activities are considered “operating.” Short-term investments having original maturities of three months or less when purchased are considered to be cash equivalents for purposes of the financial statements. Effective October 1, 2016, AFG early adopted (on a retrospective basis) ASU 2016-15, which addresses the diversity in practice in how certain cash receipts and cash payments are presented in the statement of cash flows. Among other things, this guidance requires proceeds received from the settlement of corporate-owned life insurance policies to be classified as cash inflows from investing activities and allows premiums paid for policies to be reported as cash outflows either from investing activities or operating activities. AFG has elected to show all corporate-owned life insurance activity in investing activities. Prior to adoption of this guidance, AFG accounted for these transactions as operating activities. In addition, ASU 2016-15 clarifies when distributions received from investees accounted under the equity method should be accounted for as a cash inflow from operating activities or as a cash inflow from investing activities. AFG had previously accounted for all distributions from investments accounted for under the equity method as investing activities. The new guidance solely related to the presentation of certain transactions in the statement of cash flows. Accordingly, adoption of this guidance did not impact AFG’s results of operations or financial position. Revenue Recognition Guidance Effective in 2018 In May 2014, the FASB issued ASU 2014-09, which requires an entity to recognize revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. Revenue is recognized when (or as) the entity satisfies a performance obligation under the contract. The new guidance also updates the accounting for certain costs associated with obtaining and fulfilling contracts with customers and requires disclosures regarding the nature, amount, timing and uncertainty of revenue and cash flows arising from contracts with customers. Revenue recognition for insurance contracts and financial instruments, which are AFG’s primary sources of revenue, is excluded from the scope of the new guidance. AFG will adopt the new guidance effective January 1, 2018. Because the new guidance would have applied to 2% of AFG’s 2017 consolidated revenues and the impact of the new guidance on the recognition of those revenues would not have been material, management does not expect the new guidance to have a material impact on AFG’s results of operations and financial position.

Acquisitions and Sale of Busine

Acquisitions and Sale of Businesses	12 Months Ended
	Dec. 31, 2017
Business Combinations [Abstract]
Acquisitions and Sale of Businesses	Acquisitions and Sale of Businesses Neon Lloyd’s Business On December 29, 2017, AFG completed the sale of an indirect noncontrolling interest in Neon, its United Kingdom-based Lloyd’s insurer, to certain Neon executives for cash equal to the fair value of the interest sold as determined by a third-party valuation firm. Because AFG continues to have a controlling interest in Neon, the sale was accounted for as an equity transaction with the excess of the carrying value of the net assets attributable to the noncontrolling interest sold over the consideration received recorded as a $3 million reduction in AFG’s Capital Surplus. As discussed in Note L — “ Income Taxes ,” the sale of the noncontrolling interest also resulted in the recognition of a $56 million tax benefit, including a $48 million tax benefit previously deferred in the 2016 restructuring of the Neon Lloyd’s operations. Acquisition of Noncontrolling Interest in National Interstate Corporation On November 10, 2016, AFG acquired the 49% of National Interstate Corporation (“NATL”) not previously owned by AFG’s wholly-owned subsidiary, Great American Insurance Company for $315 million ( $32.00 per share) in a merger transaction. In addition, NATL paid a one-time special cash dividend of $0.50 per share to its shareholders immediately prior to the merger closing ( $5 million was paid to noncontrolling shareholders). Expenses related to the merger were approximately $10 million and were expensed as incurred. Because NATL was already a consolidated subsidiary of AFG prior to the merger, the acquisition was accounted for as an equity transaction. As a result, the excess of the consideration paid over the carrying value of the noncontrolling interest acquired was recorded as a $137 million reduction in AFG’s Capital Surplus. In addition, the merger allowed NATL and its subsidiaries to become members of the AFG consolidated tax group, which resulted in a tax benefit of $66 million in the fourth quarter of 2016. Sale of Long-term Care Business In December 2015, AFG completed the sale of substantially all of its run-off long-term care insurance business (which was included in the run-off long-term care and life segment) to HC2 Holdings, Inc. (“HC2”) for approximately $13 million in net proceeds. AFG may also receive up to $13 million of additional proceeds from HC2 in the future contingent upon the release of certain statutory-basis liabilities of the legal entities sold by AFG. In connection with obtaining regulatory approval for the transaction, AFG agreed to provide up to an aggregate of $35 million of capital support for the insurance companies, on an as-needed basis to maintain specified surplus levels, subject to immediate reimbursement by HC2 through a five -year capital maintenance agreement. The legal entities involved in the transaction, United Teacher Associates Insurance Company (“UTA”) and Continental General Insurance Company (“CGIC”), contained substantially all of AFG’s long-term care insurance reserves ( 96% as measured by net statutory reserves as of November 30, 2015), as well as smaller blocks of annuity and life insurance business. Following the sale of these subsidiaries, AFG has only a small block of long-term care insurance ( 1,600 policies) with approximately $39 million in reserves at December 31, 2017 . AFG had ceased new sales of long-term care insurance in January 2010, but continued to accept renewal premiums on its outstanding policies, which are guaranteed renewable. In addition to the net proceeds received at closing and the $13 million of potential additional proceeds in the future from the release of statutory liabilities, AFG received a total of $97 million in tax benefits in 2016 related to the sale through reduced estimated tax payments and a tax refund resulting from the carryback of the tax-basis capital loss. The receivables for these tax benefits were reflected in AFG’s financial statements at December 31, 2015. Based on the status of ongoing negotiations at the end of the first quarter of 2015, management determined that the potential sale of the run-off long-term care insurance business met the GAAP “held for sale” criteria as of March 31, 2015. Accordingly, AFG recorded a $162 million pretax loss ( $105 million loss after tax) in the first quarter of 2015 to establish a liability equal to the excess of the net carrying value of the assets and liabilities to be disposed over the estimated net sale proceeds. At the closing date, the loss was adjusted to $166 million ( $108 million loss after tax) based on the actual proceeds received and the final carrying value of the net assets disposed. In the second quarter of 2016, AFG received additional proceeds based on the final closing balance sheet and adjusted certain accrued expense estimates associated with the sale, resulting in a $2 million pretax gain. At March 31, 2015 and at the sale date, the carrying value of the assets and liabilities disposed represented approximately 4% of both AFG’s assets and liabilities. Under accounting guidance effective in January 2015, only disposals of components of an entity that represent a strategic shift and that have a major effect on a reporting entity’s operations and financial results are reported as discontinued operations. Due to the run-off nature of the business and the immaterial expected impact on AFG’s results of operations, the sale of AFG’s long-term care insurance business has not been reported as a discontinued operation. The impact of the sale of the run-off long-term care insurance business is shown below (in millions): December 24, 2015 Net sale proceeds (*) $ 13 Assets of businesses sold: Cash and investments $ 1,334 Recoverables from reinsurers 630 Deferred policy acquisition costs 16 Other receivables 16 Other assets (4 ) Goodwill 2 Total assets 1,994 Liabilities of businesses sold: Annuity benefits accumulated 261 Life, accident and health reserves 1,525 Other liabilities 7 Total liabilities 1,793 Reclassify net unrealized gain on marketable securities 22 Net assets of businesses sold 179 Loss on subsidiaries, pretax (166 ) Tax benefit 58 Loss on subsidiaries, net of tax $ (108 ) (*) Includes the fair value of the potential additional consideration and capital maintenance agreement and is shown net of estimated expenses. Revenues, costs and expenses, and earnings before income taxes for the subsidiaries sold were (in millions): Year ended December 31, 2015 Life, accident and health net earned premiums: Long-term care $ 73 Life operations 11 Net investment income 73 Realized gains (losses) on securities and other income (11 ) Total revenues 146 Annuity benefits 8 Life, accident and health benefits: Long-term care 91 Life operations 11 Annuity and supplemental insurance acquisition expenses 12 Other expenses 16 Total costs and expenses 138 Earnings before income taxes $ 8 Other In addition to the loss on the sale of substantially all of AFG’s run-off long-term care insurance business (discussed above), AFG recorded a $5 million pretax realized gain in the third quarter of 2015 representing an adjustment to a previously recognized realized loss on a small property and casualty subsidiary sold several years ago.

Segments of Operations

Segments of Operations	12 Months Ended
	Dec. 31, 2017
Segment Reporting [Abstract]
Segments of Operations	Segments of Operations AFG manages its business as four segments: (i) Property and casualty insurance, (ii) Annuity, (iii) Run-off long-term care and life and (iv) Other, which includes holding company assets and costs, and the assets and operations attributable to the noncontrolling interests of the managed investment entities. AFG reports its property and casualty insurance business in the following Specialty sub-segments: (i) Property and transportation, which includes physical damage and liability coverage for buses, trucks and recreational vehicles, inland and ocean marine, agricultural-related products and other property coverages, (ii) Specialty casualty, which includes primarily excess and surplus, general liability, executive liability, professional liability, umbrella and excess liability, specialty coverage in targeted markets, customized programs for small to mid-sized businesses and workers’ compensation insurance, and (iii) Specialty financial, which includes risk management insurance programs for leasing and financing institutions (including collateral and lender-placed mortgage property insurance), surety and fidelity products and trade credit insurance. Premiums and underwriting profit included under Other specialty represent business assumed by AFG’s internal reinsurance program from the operations that make up AFG’s other Specialty sub-segments and amortization of deferred gains on retroactive reinsurance transactions related to the sales of businesses in prior years. AFG’s annuity business markets traditional fixed and fixed-indexed annuities in the retail, financial institutions and education markets. AFG’s reportable segments and their components were determined based primarily upon similar economic characteristics, products and services. Sales of property and casualty insurance outside of the United States represented 5% of AFG’s revenues in 2017 and 4% of AFG’s revenues in 2016 and 2015 . The following tables (in millions) show AFG’s assets, revenues and earnings before income taxes by segment and sub-segment. 2017 2016 2015 Assets Property and casualty insurance (a) $ 17,171 $ 15,574 $ 14,689 Annuity 37,179 33,409 29,865 Run-off long-term care and life 730 752 772 Other 5,578 5,337 4,511 Total assets $ 60,658 $ 55,072 $ 49,837 Revenues Property and casualty insurance: Premiums earned: Specialty Property and transportation $ 1,711 $ 1,662 $ 1,599 Specialty casualty 2,186 2,006 2,011 Specialty financial 576 557 517 Other specialty 106 103 97 Total premiums earned 4,579 4,328 4,224 Net investment income 362 350 319 Other income (b) 28 51 78 Total property and casualty insurance 4,969 4,729 4,621 Annuity: Net investment income 1,458 1,356 1,224 Other income 103 103 98 Total annuity 1,561 1,459 1,322 Run-off long-term care and life (c) 47 49 188 Other 283 240 194 Total revenues before realized gains (losses) 6,860 6,477 6,325 Realized gains (losses) on securities 5 19 (19 ) Realized gains (losses) on subsidiaries — 2 (161 ) Total revenues $ 6,865 $ 6,498 $ 6,145 (a) Not allocable to sub-segments. (b) Includes income of $32 million (before noncontrolling interest) from the sale of an apartment property in 2016 and $66 million (before noncontrolling interest) from the sales of a hotel and an apartment property in 2015. (c) AFG sold substantially all of its run-off long-term care insurance business in December 2015. 2017 2016 2015 Earnings Before Income Taxes Property and casualty insurance: Underwriting: Specialty Property and transportation $ 154 $ 166 $ 48 Specialty casualty 104 78 146 Specialty financial 61 84 87 Other specialty (2 ) 9 14 Other lines (a) (75 ) (101 ) (70 ) Total underwriting 242 236 225 Investment and other income, net (b) 349 341 351 Total property and casualty insurance 591 577 576 Annuity 380 368 331 Run-off long-term care and life (c) 6 2 14 Other (d) (258 ) (181 ) (176 ) Total earnings before realized gains (losses) and income taxes 719 766 745 Realized gains (losses) on securities 5 19 (19 ) Realized gains (losses) on subsidiaries — 2 (161 ) Total earnings before income taxes $ 724 $ 787 $ 565 (a) Includes special charges to increase asbestos and environmental (“A&E”) reserves of $89 million , $36 million and $67 million in 2017 , 2016 and 2015 , respectively. Also includes $18 million in favorable development related to the Neon exited lines recorded in connection with a reinsurance to close transaction in 2017 and a charge of $65 million related to Neon exited lines in 2016. (b) Includes income of $32 million (before noncontrolling interest) from the sale of an apartment property in 2016 and $66 million (before noncontrolling interest) from the sales of a hotel and an apartment property in 2015. (c) AFG sold substantially all of its run-off long-term care insurance business in December 2015. (d) Primarily holding company interest and expenses, including losses on retirement of debt of $51 million in 2017 and $4 million in 2015, and special charges to increase A&E reserves related to AFG’s former railroad and manufacturing operations ( $24 million in 2017 , $5 million in 2016 and $12 million in 2015 ).

Fair Value Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2017
Fair Value Disclosures [Abstract]
Fair Value Measurements	Fair Value Measurements Accounting standards for measuring fair value are based on inputs used in estimating fair value. The three levels of the hierarchy are as follows: Level 1 — Quoted prices for identical assets or liabilities in active markets (markets in which transactions occur with sufficient frequency and volume to provide pricing information on an ongoing basis). AFG’s Level 1 financial instruments consist primarily of publicly traded equity securities and highly liquid government bonds for which quoted market prices in active markets are available and short-term investments of managed investment entities. Level 2 — Quoted prices for similar instruments in active markets; quoted prices for identical or similar assets or liabilities in inactive markets (markets in which there are few transactions, the prices are not current, price quotations vary substantially over time or among market makers, or in which little information is released publicly); and valuations based on other significant inputs that are observable in active markets. AFG’s Level 2 financial instruments include separate account assets, corporate and municipal fixed maturity securities, asset-backed securities, mortgage-backed securities (“MBS”) and investments of managed investment entities priced using observable inputs. Level 2 inputs include benchmark yields, reported trades, corroborated broker/dealer quotes, issuer spreads and benchmark securities. When non-binding broker quotes can be corroborated by comparison to similar securities priced using observable inputs, they are classified as Level 2. Level 3 — Valuations derived from market valuation techniques generally consistent with those used to estimate the fair values of Level 2 financial instruments in which one or more significant inputs are unobservable or when the market for a security exhibits significantly less liquidity relative to markets supporting Level 2 fair value measurements. The unobservable inputs may include management’s own assumptions about the assumptions market participants would use based on the best information available at the valuation date. AFG’s Level 3 is comprised of financial instruments whose fair value is estimated based on non-binding broker quotes or internally developed using significant inputs not based on, or corroborated by, observable market information. As discussed in Note A — “ Accounting Policies — Managed Investment Entities ,” AFG has set the carrying value of its CLO liabilities equal to the fair value of the CLO assets (which have more observable fair values) as an alternative to reporting those liabilities at separately measured fair values. As a result, the CLO liabilities are categorized within the fair value hierarchy on the same basis (proportionally) as the related CLO assets. Since the portion of the CLO liabilities allocated to Level 3 is derived from the fair value of the CLO assets, these amounts are excluded from the progression of Level 3 financial instruments. AFG’s management is responsible for the valuation process and uses data from outside sources (including nationally recognized pricing services and broker/dealers) in establishing fair value. AFG’s internal investment professionals are a group of approximately 25 analysts whose primary responsibility is to manage AFG’s investment portfolio. These professionals monitor individual investments as well as overall industries and are active in the financial markets on a daily basis. The group is led by AFG’s chief investment officer, who reports directly to one of AFG’s Co-CEOs. Valuation techniques utilized by pricing services and prices obtained from external sources are reviewed by AFG’s internal investment professionals who are familiar with the securities being priced and the markets in which they trade to ensure the fair value determination is representative of an exit price. To validate the appropriateness of the prices obtained, these investment managers consider widely published indices (as benchmarks), recent trades, changes in interest rates, general economic conditions and the credit quality of the specific issuers. In addition, the Company communicates directly with the pricing services regarding the methods and assumptions used in pricing, including verifying, on a test basis, the inputs used by the service to value specific securities. Assets and liabilities measured and carried at fair value in the financial statements are summarized below (in millions): Level 1 Level 2 Level 3 Total December 31, 2017 Assets: Available for sale (“AFS”) fixed maturities: U.S. Government and government agencies $ 122 $ 112 $ 8 $ 242 States, municipalities and political subdivisions — 6,975 148 7,123 Foreign government — 127 — 127 Residential MBS — 3,105 122 3,227 Commercial MBS — 926 36 962 Asset-backed securities (“ABS”) — 7,218 744 7,962 Corporate and other 30 17,662 1,044 18,736 Total AFS fixed maturities 152 36,125 2,102 38,379 Trading fixed maturities 44 304 — 348 Equity securities — AFS and trading 1,411 86 165 1,662 Assets of managed investment entities (“MIE”) 307 4,572 23 4,902 Variable annuity assets (separate accounts) (*) — 644 — 644 Equity index call options — 701 — 701 Other assets — derivatives — — — — Total assets accounted for at fair value $ 1,914 $ 42,432 $ 2,290 $ 46,636 Liabilities: Liabilities of managed investment entities $ 293 $ 4,372 $ 22 $ 4,687 Derivatives in annuity benefits accumulated — — 2,542 2,542 Other liabilities — derivatives — 35 — 35 Total liabilities accounted for at fair value $ 293 $ 4,407 $ 2,564 $ 7,264 December 31, 2016 Assets: Available for sale fixed maturities: U.S. Government and government agencies $ 133 $ 174 $ 8 $ 315 States, municipalities and political subdivisions — 6,641 140 6,781 Foreign government — 136 — 136 Residential MBS — 3,445 190 3,635 Commercial MBS — 1,468 25 1,493 Asset-backed securities — 5,475 484 5,959 Corporate and other 29 15,484 712 16,225 Total AFS fixed maturities 162 32,823 1,559 34,544 Trading fixed maturities 30 329 — 359 Equity securities — AFS and trading 1,305 79 174 1,558 Assets of managed investment entities 380 4,356 29 4,765 Variable annuity assets (separate accounts) (*) — 600 — 600 Equity index call options — 492 — 492 Other assets — derivatives — 1 — 1 Total assets accounted for at fair value $ 1,877 $ 38,680 $ 1,762 $ 42,319 Liabilities: Liabilities of managed investment entities $ 363 $ 4,158 $ 28 $ 4,549 Derivatives in annuity benefits accumulated — — 1,759 1,759 Derivatives in long-term debt — (1 ) — (1 ) Other liabilities — derivatives — 30 — 30 Total liabilities accounted for at fair value $ 363 $ 4,187 $ 1,787 $ 6,337 (*) Variable annuity liabilities equal the fair value of variable annuity assets. The transfers between Level 1 and Level 2 for the years ended December 31, 2017 , 2016 and 2015 are reflected in the table below at fair value as of the end of the reporting period (dollars in millions): Level 2 To Level 1 Transfers Level 1 To Level 2 Transfers # of Transfers Fair Value # of Transfers Fair Value 2017 2016 2015 2017 2016 2015 2017 2016 2015 2017 2016 2015 Perpetual preferred stocks 4 6 5 $ 23 $ 35 $ 19 2 7 7 $ 11 $ 28 $ 31 Common stocks — 3 7 — — 80 1 2 — — — — Redeemable preferred stocks — — 2 — — 11 — — — — — — Transfers between Level 1 and Level 2 for all periods presented were a result of increases or decreases in observable trade activity. Approximately 5% of the total assets carried at fair value on December 31, 2017 , were Level 3 assets. Approximately 79% ( $1.80 billion ) of the Level 3 assets were priced using non-binding broker quotes, for which there is a lack of transparency as to the inputs used to determine fair value. Details as to the quantitative inputs are neither provided by the brokers nor otherwise reasonably obtainable by AFG. Since internally developed Level 3 asset fair values represent less than 10% of AFG’s Shareholders’ Equity, any justifiable changes in unobservable inputs used to determine internally developed fair values would not have a material impact on AFG’s financial position. The only significant Level 3 assets or liabilities carried at fair value in the financial statements that were not measured using broker quotes are the derivatives embedded in AFG’s fixed-indexed annuity liabilities, which are measured using a discounted cash flow approach and had a fair value of $2.54 billion at December 31, 2017 . The following table presents information about the unobservable inputs used by management in determining fair value of these embedded derivatives. See Note F — “ Derivatives .” Unobservable Input Range Adjustment for insurance subsidiary’s credit risk 0.2% – 2.0% over the risk free rate Risk margin for uncertainty in cash flows 0.70% reduction in the discount rate Surrenders 3% – 23% of indexed account value Partial surrenders 2% – 10% of indexed account value Annuitizations 0.1% – 1% of indexed account value Deaths 1.6% – 8.0% of indexed account value Budgeted option costs 2.4% – 3.6% of indexed account value The range of adjustments for insurance subsidiary’s credit risk reflects credit spread variations across the yield curve. The range of projected surrender rates reflects the specific surrender charges and other features of AFG’s individual fixed-indexed annuity products with an expected range of 6% to 10% in the majority of future calendar years ( 3% to 23% over all periods). Increasing the budgeted option cost or risk margin for uncertainty in cash flow assumptions in the table above would increase the fair value of the fixed-indexed annuity embedded derivatives, while increasing any of the other unobservable inputs in the table above would decrease the fair value of the embedded derivatives. Changes in balances of Level 3 financial assets and liabilities carried at fair value during 2017 , 2016 and 2015 are presented below (in millions). The transfers into and out of Level 3 were due to changes in the availability of market observable inputs. All transfers are reflected in the table at fair value as of the end of the reporting period. Total realized/unrealized gains (losses) included in Balance at December 31, 2016 Net earnings Other comprehensive income (loss) Purchases and issuances Sales and settlements Transfer into Level 3 Transfer out of Level 3 Balance at December 31, 2017 AFS fixed maturities: U.S. government agency $ 8 $ — $ — $ — $ — $ — $ — $ 8 State and municipal 140 — 2 — (2 ) 10 (2 ) 148 Residential MBS 190 (4 ) 2 1 (40 ) 44 (71 ) 122 Commercial MBS 25 2 — 15 (10 ) 4 — 36 Asset-backed securities 484 — 1 410 (132 ) 202 (221 ) 744 Corporate and other 712 (5 ) 2 606 (237 ) 29 (63 ) 1,044 Total AFS fixed maturities 1,559 (7 ) 7 1,032 (421 ) 289 (357 ) 2,102 Equity securities 174 (21 ) 10 38 (16 ) — (20 ) 165 Assets of MIE 29 (11 ) — 9 — — (4 ) 23 Total Level 3 assets $ 1,762 $ (39 ) $ 17 $ 1,079 $ (437 ) $ 289 $ (381 ) $ 2,290 Embedded derivatives (a) $ (1,759 ) $ (589 ) $ — $ (300 ) $ 106 $ — $ — $ (2,542 ) Total Level 3 liabilities (b) $ (1,759 ) $ (589 ) $ — $ (300 ) $ 106 $ — $ — $ (2,542 ) (a) Total realized/unrealized gains (losses) included in net earnings for the embedded derivatives reflects losses related to the unlocking of actuarial assumptions of $25 million in 2017 . (b) As previously discussed, these tables exclude the portion of MIE liabilities allocated to Level 3, which are derived from the fair value of the MIE assets. Total realized/unrealized Balance at December 31, 2015 Net Other Purchases Sales and Transfer Transfer Balance at December 31, 2016 AFS fixed maturities: U.S. government agency $ 15 $ (8 ) $ 1 $ — $ — $ — $ — $ 8 State and municipal 89 — (4 ) 57 (2 ) — — 140 Residential MBS 224 (4 ) (2 ) 8 (28 ) 34 (42 ) 190 Commercial MBS 39 (1 ) — — (7 ) — (6 ) 25 Asset-backed securities 470 (1 ) 1 50 (52 ) 60 (44 ) 484 Corporate and other 633 — (10 ) 176 (100 ) 30 (17 ) 712 Total AFS fixed maturities 1,470 (14 ) (14 ) 291 (189 ) 124 (109 ) 1,559 Equity securities 140 (12 ) 35 44 (28 ) 15 (20 ) 174 Assets of MIE 26 (9 ) — 12 — — — 29 Total Level 3 assets $ 1,636 $ (35 ) $ 21 $ 347 $ (217 ) $ 139 $ (129 ) $ 1,762 Embedded derivatives (a) $ (1,369 ) $ (211 ) $ — $ (277 ) $ 98 $ — $ — $ (1,759 ) Total Level 3 liabilities (b) $ (1,369 ) $ (211 ) $ — $ (277 ) $ 98 $ — $ — $ (1,759 ) (a) Total realized/unrealized gains (losses) included in net earnings for the embedded derivatives reflects losses related to the unlocking of actuarial assumptions of $17 million in 2016 . (b) As previously discussed, these tables exclude the portion of MIE liabilities allocated to Level 3, which are derived from the fair value of the MIE assets. Total realized/unrealized gains (losses) included in Bal. at Dec. 31, 2014 Impact of Net earnings Other comprehensive income (loss) Purchases and issuances Sales and settlements Transfer into Level 3 Transfer out of Level 3 Sale of subsidiaries Bal. at Dec. 31, 2015 AFS fixed maturities: U.S. government agency $ 15 $ — $ — $ — $ — $ — $ — $ — $ — $ 15 State and municipal 100 — — (1 ) 34 (1 ) 2 (39 ) (6 ) 89 Residential MBS 300 — (11 ) (1 ) — (34 ) 86 (88 ) (28 ) 224 Commercial MBS 44 — (1 ) (1 ) — (2 ) 4 (1 ) (4 ) 39 Asset-backed securities 226 — 1 (7 ) 265 (56 ) 53 (10 ) (2 ) 470 Corporate and other 546 — (5 ) (9 ) 161 (90 ) 41 (5 ) (6 ) 633 Total AFS fixed maturities 1,231 — (16 ) (19 ) 460 (183 ) 186 (143 ) (46 ) 1,470 Equity securities 93 — (4 ) (9 ) 77 — — (17 ) — 140 Assets of MIE 31 — (11 ) — 6 — — — — 26 Total Level 3 assets $ 1,355 $ — $ (31 ) $ (28 ) $ 543 $ (183 ) $ 186 $ (160 ) $ (46 ) $ 1,636 Liabilities of MIE $ (2,701 ) $ 2,701 $ — $ — $ — $ — $ — $ — $ — $ — Embedded derivatives (a) (1,160 ) — (17 ) — (257 ) 65 — — — (1,369 ) Total Level 3 liabilities $ (3,861 ) $ 2,701 $ (17 ) $ — $ (257 ) $ 65 $ — $ — $ — $ (1,369 ) (a) Total realized/unrealized gains (losses) included in net earnings for the embedded derivatives reflects losses related to the unlocking of actuarial assumptions of $28 million in 2015 . (b) The impact of implementing new guidance adopted in 2015, as discussed in Note A — “ Accounting Policies — Managed Investment Entities .” Fair Value of Financial Instruments The carrying value and fair value of financial instruments that are not carried at fair value in the financial statements at December 31 are summarized below (in millions): Carrying Fair Value Value Total Level 1 Level 2 Level 3 2017 Financial assets: Cash and cash equivalents $ 2,338 $ 2,338 $ 2,338 $ — $ — Mortgage loans 1,125 1,119 — — 1,119 Policy loans 184 184 — — 184 Total financial assets not accounted for at fair value $ 3,647 $ 3,641 $ 2,338 $ — $ 1,303 Financial liabilities: Annuity benefits accumulated (*) $ 33,110 $ 32,461 $ — $ — $ 32,461 Long-term debt 1,301 1,354 — 1,351 3 Total financial liabilities not accounted for at fair value $ 34,411 $ 33,815 $ — $ 1,351 $ 32,464 2016 Financial assets: Cash and cash equivalents $ 2,107 $ 2,107 $ 2,107 $ — $ — Mortgage loans 1,147 1,146 — — 1,146 Policy loans 192 192 — — 192 Total financial assets not accounted for at fair value $ 3,446 $ 3,445 $ 2,107 $ — $ 1,338 Financial liabilities: Annuity benefits accumulated (*) $ 29,703 $ 28,932 $ — $ — $ 28,932 Long-term debt 1,284 1,356 — 1,353 3 Total financial liabilities not accounted for at fair value $ 30,987 $ 30,288 $ — $ 1,353 $ 28,935 (*) Excludes $206 million and $204 million of life contingent annuities in the payout phase at December 31, 2017 and 2016 , respectively. The carrying amount of cash and cash equivalents approximates fair value. Fair values for mortgage loans are estimated by discounting the future contractual cash flows using the current rates at which similar loans would be made to borrowers with similar credit ratings. The fair value of policy loans is estimated to approximate carrying value; policy loans have no defined maturity dates and are inseparable from insurance contracts. The fair value of annuity benefits was estimated based on expected cash flows discounted using forward interest rates adjusted for the Company’s credit risk and includes the impact of maintenance expenses and capital costs. Fair values of long-term debt are based primarily on quoted market prices.

Investments

Investments	12 Months Ended
	Dec. 31, 2017
Investments, Debt and Equity Securities [Abstract]
Investments	Investments Available for sale fixed maturities and equity securities at December 31 consisted of the following (in millions): 2017 2016 Amortized Cost Gross Unrealized Net Unrealized Fair Value Amortized Cost Gross Unrealized Net Unrealized Fair Value Gains Losses Gains Losses Fixed maturities: U.S. Government and government agencies $ 244 $ 1 $ (3 ) $ (2 ) $ 242 $ 315 $ 3 $ (3 ) $ — $ 315 States, municipalities and political subdivisions 6,887 254 (18 ) 236 7,123 6,650 200 (69 ) 131 6,781 Foreign government 124 3 — 3 127 131 5 — 5 136 Residential MBS 2,884 349 (6 ) 343 3,227 3,367 281 (13 ) 268 3,635 Commercial MBS 927 36 (1 ) 35 962 1,446 49 (2 ) 47 1,493 Asset-backed securities 7,836 142 (16 ) 126 7,962 5,962 43 (46 ) (3 ) 5,959 Corporate and other 18,136 638 (38 ) 600 18,736 15,864 473 (112 ) 361 16,225 Total fixed maturities $ 37,038 $ 1,423 $ (82 ) $ 1,341 $ 38,379 $ 33,735 $ 1,054 $ (245 ) $ 809 $ 34,544 Equity Securities: Common stocks $ 786 $ 263 $ (22 ) $ 241 $ 1,027 $ 879 $ 160 $ (23 ) $ 137 $ 1,016 Perpetual preferred stocks 535 39 (1 ) 38 573 472 21 (7 ) 14 486 Total equity securities $ 1,321 $ 302 $ (23 ) $ 279 $ 1,600 $ 1,351 $ 181 $ (30 ) $ 151 $ 1,502 The non-credit related portion of other-than-temporary impairment charges is included in other comprehensive income. Cumulative non-credit charges taken for securities still owned at December 31, 2017 and December 31, 2016 , respectively, were $158 million and $189 million . Gross unrealized gains on such securities at December 31, 2017 and December 31, 2016 were $137 million and $130 million , respectively. Gross unrealized losses on such securities at December 31, 2017 and December 31, 2016 were $4 million and $3 million , respectively. These amounts represent the non-credit other-than-temporary impairment charges recorded in AOCI adjusted for subsequent changes in fair values and relate primarily to residential MBS. The following tables show gross unrealized losses (dollars in millions) on available for sale fixed maturities and equity securities by investment category and length of time that individual securities have been in a continuous unrealized loss position at December 31, 2017 and 2016 . Less Than Twelve Months Twelve Months or More Unrealized Loss Fair Value Fair Value as % of Cost Unrealized Loss Fair Value Fair Value as % of Cost 2017 Fixed maturities: U.S. Government and government agencies $ — $ 55 100 % $ (3 ) $ 123 98 % States, municipalities and political subdivisions (8 ) 825 99 % (10 ) 431 98 % Foreign government — 4 100 % — — — % Residential MBS (1 ) 118 99 % (5 ) 118 96 % Commercial MBS (1 ) 67 99 % — — — % Asset-backed securities (7 ) 1,195 99 % (9 ) 299 97 % Corporate and other (20 ) 2,031 99 % (18 ) 603 97 % Total fixed maturities $ (37 ) $ 4,295 99 % $ (45 ) $ 1,574 97 % Equity securities: Common stocks $ (22 ) $ 117 84 % $ — $ — — % Perpetual preferred stocks — 41 100 % (1 ) 13 93 % Total equity securities $ (22 ) $ 158 88 % $ (1 ) $ 13 93 % 2016 Fixed maturities: U.S. Government and government agencies $ (1 ) $ 153 99 % $ (2 ) $ 8 80 % States, municipalities and political subdivisions (64 ) 2,289 97 % (5 ) 44 90 % Residential MBS (7 ) 502 99 % (6 ) 162 96 % Commercial MBS (2 ) 121 98 % — — — % Asset-backed securities (29 ) 1,737 98 % (17 ) 634 97 % Corporate and other (93 ) 3,849 98 % (19 ) 312 94 % Total fixed maturities $ (196 ) $ 8,651 98 % $ (49 ) $ 1,160 96 % Equity securities: Common stocks $ (23 ) $ 215 90 % $ — $ — — % Perpetual preferred stocks (6 ) 135 96 % (1 ) 6 86 % Total equity securities $ (29 ) $ 350 92 % $ (1 ) $ 6 86 % At December 31, 2017 , the gross unrealized losses on fixed maturities of $82 million relate to 841 securities. Investment grade securities (as determined by nationally recognized rating agencies) represented approximately 78% of the gross unrealized loss and 90% of the fair value. The determination of whether unrealized losses are “other-than-temporary” requires judgment based on subjective as well as objective factors. Factors considered and resources used by management include: a) whether the unrealized loss is credit-driven or a result of changes in market interest rates, b) the extent to which fair value is less than cost basis, c) cash flow projections received from independent sources, d) historical operating, balance sheet and cash flow data contained in issuer SEC filings and news releases, e) near-term prospects for improvement in the issuer and/or its industry, f) third party research and communications with industry specialists, g) financial models and forecasts, h) the continuity of dividend payments, maintenance of investment grade ratings and hybrid nature of certain investments, i) discussions with issuer management, and j) ability and intent to hold the investment for a period of time sufficient to allow for anticipated recovery in fair value. AFG analyzes its MBS securities for other-than-temporary impairment each quarter based upon expected future cash flows. Management estimates expected future cash flows based upon its knowledge of the MBS market, cash flow projections (which reflect loan to collateral values, subordination, vintage and geographic concentration) received from independent sources, implied cash flows inherent in security ratings and analysis of historical payment data. During 2017 , AFG recorded $1 million in other-than-temporary impairment charges related to its residential MBS. In 2017 , AFG recorded approximately $19 million and $4 million in other-than-temporary impairment charges related to other fixed maturities (other than residential MBS securities) and other investments, respectively. AFG recorded $55 million in other-than-temporary impairment charges on common stocks in 2017 . At December 31, 2017 , the gross unrealized losses on common stocks of $22 million relate to 16 securities, none of which has been in an unrealized loss position for more than 12 months. AFG recorded $9 million in other-than-temporary impairment charges on preferred stock in 2017. At December 31, 2017 , the gross unrealized losses on preferred stocks of $1 million relate to 7 securities. Three preferred stocks have been in an unrealized loss position for 12 months or more and all are investment grade rated. Management believes AFG will recover its cost basis in the securities with unrealized losses and that AFG has the ability to hold the securities until they recover in value and had no intent to sell them at December 31, 2017 . As discussed in Note A — “ Accounting Policies — Investments ,” effective January 1, 2018, all equity securities currently classified as “available for sale” will be required to be carried at fair value through net earnings instead of accumulated other comprehensive income and will therefore no longer be evaluated for other-than-temporary impairment. A progression of the credit portion of other-than-temporary impairments on fixed maturity securities for which the non-credit portion of an impairment has been recognized in other comprehensive income is shown below (in millions): 2017 2016 2015 Balance at January 1 $ 153 $ 160 $ 170 Additional credit impairments on: Previously impaired securities 1 2 1 Securities without prior impairments 3 1 2 Reductions due to: Sales or redemptions (12 ) (10 ) (9 ) Sale of subsidiaries — — (4 ) Balance at December 31 $ 145 $ 153 $ 160 The table below sets forth the scheduled maturities of available for sale fixed maturities as of December 31, 2017 (dollars in millions). Securities with sinking funds are reported at average maturity. Actual maturities may differ from contractual maturities because certain securities may be called or prepaid by the issuers. Amortized Fair Value Cost Amount % Maturity One year or less $ 746 $ 759 2 % After one year through five years 6,730 6,939 18 % After five years through ten years 13,235 13,662 35 % After ten years 4,680 4,868 13 % 25,391 26,228 68 % ABS (average life of approximately 5 years) 7,836 7,962 21 % MBS (average life of approximately 4.5 years) 3,811 4,189 11 % Total $ 37,038 $ 38,379 100 % Certain risks are inherent in fixed maturity securities, including loss upon default, price volatility in reaction to changes in interest rates, and general market factors and risks associated with reinvestment of proceeds due to prepayments or redemptions in a period of declining interest rates. There were no investments in individual issuers that exceeded 10% of shareholders’ equity at December 31, 2017 or 2016 . Net Unrealized Gain on Marketable Securities In addition to adjusting fixed maturity securities and equity securities classified as “available for sale” to fair value, GAAP requires that deferred policy acquisition costs and certain other balance sheet amounts related to annuity, long-term care and life businesses be adjusted to the extent that unrealized gains and losses from securities would result in adjustments to those balances had the unrealized gains or losses actually been realized. The following table shows (in millions) the components of the net unrealized gain on securities that is included in AOCI in AFG’s Balance Sheet. Pretax Deferred Tax Net December 31, 2017 Net unrealized gain on: Fixed maturities — annuity segment (a) $ 1,082 $ (227 ) $ 855 Fixed maturities — all other 259 (55 ) 204 Total fixed maturities 1,341 (282 ) 1,059 Equity securities (b) 279 (58 ) 221 Total investments 1,620 (340 ) 1,280 Deferred policy acquisition costs — annuity segment (433 ) 91 (342 ) Annuity benefits accumulated (137 ) 29 (108 ) Unearned revenue 13 (3 ) 10 Total net unrealized gain on marketable securities $ 1,063 $ (223 ) $ 840 December 31, 2016 Net unrealized gain on: Fixed maturities — annuity segment (a) $ 640 $ (224 ) $ 416 Fixed maturities — all other 169 (59 ) 110 Total fixed maturities 809 (283 ) 526 Equity securities (b) 151 (53 ) 98 Total investments 960 (336 ) 624 Deferred policy acquisition costs — annuity segment (273 ) 96 (177 ) Annuity benefits accumulated (78 ) 27 (51 ) Unearned revenue 13 (5 ) 8 Total net unrealized gain on marketable securities $ 622 $ (218 ) $ 404 (a) Net unrealized gains on fixed maturity investments supporting AFG’s annuity benefits accumulated. (b) As discussed in Note A — “ Accounting Policies — Investments ,” effective January 1, 2018, all equity securities currently classified as “available for sale” will be required to be carried at fair value through net earnings instead of AOCI. Real Estate and Other Investments Real estate and other investments on AFG’s Balance Sheet includes the following at December 31 (in millions): 2017 2016 Limited partnerships and similar investments accounted for using the equity method $ 999 $ 688 Directly owned real estate 164 197 Other investments 148 149 Total real estate and other investments $ 1,311 $ 1,034 Net Investment Income The following table shows (in millions) investment income earned and investment expenses incurred. 2017 2016 2015 Investment income: Fixed maturities $ 1,607 $ 1,510 $ 1,461 Equity securities 79 81 76 Equity in earnings of partnerships and similar investments 64 44 27 Other 102 81 87 Gross investment income 1,852 1,716 1,651 Investment expenses (21 ) (20 ) (18 ) Net investment income $ 1,831 $ 1,696 $ 1,633 Realized gains (losses) and changes in unrealized appreciation (depreciation) related to fixed maturity and equity security investments are summarized as follows (in millions): 2017 2016 Realized gains (losses) Realized gains (losses) Before Impairments Impairments Total Change in Unrealized Before Impairments Impairments Total Change in Unrealized Fixed maturities $ 17 $ (20 ) $ (3 ) $ 532 $ 36 $ (38 ) $ (2 ) $ 90 Equity securities 70 (64 ) 6 128 106 (93 ) 13 67 Mortgage loans and other investments (6 ) (4 ) (10 ) — — — — — Other (*) (3 ) 15 12 (219 ) (7 ) 15 8 (52 ) Total pretax 78 (73 ) 5 441 135 (116 ) 19 105 Tax effects (27 ) 25 (2 ) (5 ) (48 ) 41 (7 ) (37 ) Noncontrolling interests — — — — (2 ) 3 1 4 Net of tax and noncontrolling interests $ 51 $ (48 ) $ 3 $ 436 $ 85 $ (72 ) $ 13 $ 72 2015 Realized gains (losses) Before Impairments Impairments Total Change in Unrealized Fixed maturities $ 19 $ (43 ) $ (24 ) $ (941 ) Equity securities 94 (94 ) — (134 ) Mortgage loans and other investments (2 ) (3 ) (5 ) — Other (*) (5 ) 15 10 430 Total pretax 106 (125 ) (19 ) (645 ) Tax effects (38 ) 45 7 226 Noncontrolling interests (2 ) 2 — 8 Net of tax and noncontrolling interests $ 66 $ (78 ) $ (12 ) $ (411 ) (*) Primarily adjustments to deferred policy acquisition costs and reserves related to the annuity business. Gross realized gains and losses (excluding impairment write-downs and mark-to-market of derivatives) on available for sale fixed maturity and equity security investment transactions consisted of the following (in millions): 2017 2016 2015 Fixed maturities: Gross gains $ 43 $ 55 $ 38 Gross losses (20 ) (10 ) (7 ) Equity securities: Gross gains 87 110 99 Gross losses (17 ) (4 ) (5 )

Derivatives

Derivatives	12 Months Ended
	Dec. 31, 2017
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivatives	Derivatives As discussed under “ Derivatives ” in Note A — “ Accounting Policies ,” AFG uses derivatives in certain areas of its operations. Derivatives That Do Not Qualify for Hedge Accounting The following derivatives that do not qualify for hedge accounting under GAAP are included in AFG’s Balance Sheet at fair value (in millions): December 31, 2017 December 31, 2016 Derivative Balance Sheet Line Asset Liability Asset Liability MBS with embedded derivatives Fixed maturities $ 105 $ — $ 107 $ — Public company warrants Equity securities 4 — 4 — Fixed-indexed annuities (embedded derivative) Annuity benefits accumulated — 2,542 — 1,759 Equity index call options Equity index call options 701 — 492 — Reinsurance contract (embedded derivative) Other liabilities — 4 — 8 $ 810 $ 2,546 $ 603 $ 1,767 The MBS with embedded derivatives consist primarily of interest-only MBS with interest rates that float inversely with short-term rates. AFG records the entire change in the fair value of these securities in earnings. These investments are part of AFG’s overall investment strategy and represent a small component of AFG’s overall investment portfolio. Warrants to purchase shares of publicly traded companies, which represent a small component of AFG’s overall investment portfolio, are considered to be derivatives that are required to be carried at fair value through earnings. AFG’s fixed-indexed annuities provide policyholders with a crediting rate tied, in part, to the performance of an existing stock market or other financial index. AFG attempts to mitigate the risk in the index-based component of these products through the purchase of call options on the appropriate index. AFG receives collateral from certain of its counterparties to support its purchased call option assets. This collateral ( $389 million at December 31, 2017 and $380 million at December 31, 2016 ) is included in other assets in AFG’s Balance Sheet with an offsetting liability to return the collateral, which is included in other liabilities. AFG’s strategy is designed so that the change in the fair value of the call option assets will generally offset the economic change in the liabilities from the index participation. Both the index-based component of the annuities and the related call options are considered derivatives. Fluctuations in interest rates and the stock market, among other factors, can cause volatility in the periodic measurement of fair value of the embedded derivative that management believes can be inconsistent with the long-term economics of these products. As discussed under “ Reinsurance ” in Note A , AFG has a reinsurance contract that is considered to contain an embedded derivative. The following table summarizes the gain (loss) included in AFG’s Statement of Earnings for changes in the fair value of derivatives that do not qualify for hedge accounting for 2017 , 2016 and 2015 (in millions): Derivative Statement of Earnings Line 2017 2016 2015 MBS with embedded derivatives Realized gains (losses) on securities $ (6 ) $ (9 ) $ (16 ) Public company warrants Realized gains (losses) on securities — — — Fixed-indexed annuities (embedded derivative) (*) Annuity benefits (589 ) (211 ) (17 ) Equity index call options Annuity benefits 494 141 (56 ) Reinsurance contracts (embedded derivative) Net investment income (2 ) (1 ) 6 $ (103 ) $ (80 ) $ (83 ) (*) The change in fair value of the embedded derivative includes losses related to unlocking of actuarial assumptions of $25 million in 2017 compared to $17 million in 2016 and $28 million in 2015 . Derivatives Designated and Qualifying as Cash Flow Hedges As of December 31, 2017 , AFG has entered into ten interest rate swaps that are designated and qualify as highly effective cash flow hedges to mitigate interest rate risk related to certain floating-rate securities included in AFG’s portfolio of fixed maturity securities. The purpose of each of these swaps is to effectively convert a portion of AFG’s floating-rate fixed maturity securities to fixed rates by offsetting the variability in cash flows attributable to changes in short-term LIBOR. Under the terms of the swaps, AFG receives fixed-rate interest payments in exchange for variable interest payments based on short-term LIBOR. The notional amounts of the interest rate swaps generally decline over each swap’s respective life (the swaps expire between August 2019 and June 2030) in anticipation of the expected decline in AFG’s portfolio of fixed maturity securities with floating interest rates based on short-term LIBOR. The total outstanding notional amount of AFG’s interest rate swaps increased to $1.58 billion at December 31, 2017 compared to $1.08 billion at December 31, 2016 , reflecting three new swaps with an aggregate notional amount at issuance of $663 million entered into in 2017 , partially offset by the scheduled amortization discussed above. The fair value of the effective portion of the interest rate swaps in an asset position and included in other assets was less than $1 million at December 31, 2017 and $1 million at December 31, 2016 . The fair value of the effective portion of interest rate swaps in a liability position and included in other liabilities was $31 million at December 31, 2017 and $22 million at December 31, 2016 . The net unrealized gain or loss on cash flow hedges is included in AOCI, net of DPAC and deferred taxes. Amounts reclassified from AOCI (before DPAC and taxes) to net investment income were $6 million in 2017 , $7 million in 2016 and $6 million in 2015 . There was no ineffectiveness recorded in net earnings during these periods. A collateral receivable supporting these swaps of $70 million at December 31, 2017 and $60 million at December 31, 2016 is included in other assets in AFG’s Balance Sheet. Derivative Designated and Qualifying as a Fair Value Hedge In June 2015, AFG entered into an interest rate swap to mitigate the interest rate risk associated with its fixed-rate 9-7/8% Senior Notes due June 2019 by effectively converting the interest rate on those notes to a floating rate of three-month LIBOR plus 8.099% . In connection with redemption of the 9-7/8% Senior Notes in December 2017, AFG paid the counterparty $1 million to settle the interest rate swap. Since the terms of the interest rate swap matched the terms of the hedged debt, changes in the fair value of the interest rate swap were offset by changes in the fair value of the hedged debt attributable to changes in interest rates. The fair value of the interest rate swap (asset of $1 million at December 31, 2016 ) and the offsetting adjustment to the carrying value of the 9-7/8% Senior Notes were both included in long-term debt on AFG’s Balance Sheet. Accordingly, the net impact on AFG’s earnings during the period that the swap was outstanding was that the interest expense associated with the hedged debt was effectively recorded at the floating rate. The net reduction in interest expense from the swap for 2017 , 2016 and 2015 was $2 million , $3 million and $2 million , respectively.

Deferred Policy Acquisition Cos

Deferred Policy Acquisition Costs	12 Months Ended
	Dec. 31, 2017
Deferred Policy Acquisition Costs Disclosures [Abstract]
Deferred Policy Acquisition Costs	Deferred Policy Acquisition Costs A progression of deferred policy acquisition costs is presented below (in millions): P&C Annuity and Run-off Long-term Care and Life Deferred Deferred Sales Consolidated Costs Costs Inducements PVFP Subtotal Unrealized (*) Total Total Balance at December 31, 2014 $ 221 $ 925 $ 132 $ 74 $ 1,131 $ (531 ) $ 600 $ 821 Additions 519 224 11 — 235 — 235 754 Amortization: Periodic amortization (511 ) (162 ) (26 ) (11 ) (199 ) — (199 ) (710 ) Annuity unlocking — 31 4 — 35 — 35 35 Included in realized gains — 8 1 — 9 — 9 9 Sale of subsidiaries — (8 ) (3 ) (8 ) (19 ) — (19 ) (19 ) Foreign currency translation (3 ) — — — — — — (3 ) Change in unrealized — — — — — 297 297 297 Balance at December 31, 2015 226 1,018 119 55 1,192 (234 ) 958 1,184 Additions 535 230 9 — 239 — 239 774 Amortization: Periodic amortization (520 ) (169 ) (24 ) (9 ) (202 ) — (202 ) (722 ) Annuity unlocking — 25 4 — 29 — 29 29 Included in realized gains — 6 2 — 8 — 8 8 Foreign currency translation (3 ) — — — — — — (3 ) Change in unrealized — — — — — (31 ) (31 ) (31 ) Balance at December 31, 2016 238 1,110 110 46 1,266 (265 ) 1,001 1,239 Additions 588 225 4 — 229 — 229 817 Amortization: Periodic amortization (556 ) (161 ) (19 ) (8 ) (188 ) — (188 ) (744 ) Annuity unlocking — 34 6 1 41 — 41 41 Included in realized gains — 9 1 — 10 — 10 10 Foreign currency translation — — — — — — — — Other — — — 10 10 — 10 10 Change in unrealized — — — — — (157 ) (157 ) (157 ) Balance at December 31, 2017 $ 270 $ 1,217 $ 102 $ 49 $ 1,368 $ (422 ) $ 946 $ 1,216 (*) Unrealized adjustments to DPAC includes net unrealized gains/losses on securities and net unrealized gains/losses on cash flow hedges. The present value of future profits (“PVFP”) amounts in the table above are net of $141 million and $134 million of accumulated amortization at December 31, 2017 and 2016 , respectively. During each of the next five years, the PVFP is expected to decrease at a rate of approximately one-eighth of the balance at the beginning of each respective year.

Managed Investment Entities

Managed Investment Entities	12 Months Ended
	Dec. 31, 2017
Variable Interest Entity, Primary Beneficiary, Does Not Hold Majority Voting Interest, Disclosures [Abstract]
Managed Investment Entities	Managed Investment Entities AFG is the investment manager and its subsidiaries have investments ranging from 15.0% to 60.9% of the most subordinate debt tranche of fifteen collateralized loan obligation entities or “CLOs,” which are considered variable interest entities. AFG’s subsidiaries also own portions of the senior debt tranches of certain of these CLOs. Upon formation between 2004 and 2017, these entities issued securities in various senior and subordinate classes and invested the proceeds primarily in secured bank loans, which serve as collateral for the debt securities issued by each particular CLO. None of the collateral was purchased from AFG. AFG’s investments in the subordinate debt tranches of these entities receive residual income from the CLOs only after the CLOs pay expenses (including management fees to AFG) and interest on and returns of capital to senior levels of debt securities. There are no contractual requirements for AFG to provide additional funding for these entities. AFG has not provided and does not intend to provide any financial support to these entities. AFG’s maximum exposure to economic loss on its CLOs is limited to its investment in the CLOs, which had an aggregate fair value of $215 million (including $130 million invested in the most subordinate tranches) at December 31, 2017 , and $216 million at December 31, 2016 . In 2017 , AFG formed two new CLOs, which issued an aggregate of $865 million face amount of liabilities (including $48 million face amount purchased by subsidiaries of AFG). During 2017 , AFG subsidiaries also purchased $71 million face amount of senior debt and subordinate tranches of existing CLOs for $71 million . During 2017 , AFG subsidiaries received $103 million in sale and redemption proceeds from its CLO investments. In 2016 , AFG formed two new CLOs, which issued an aggregate of $866 million face amount of liabilities (including $64 million face amount purchased by subsidiaries of AFG). During 2016 , AFG subsidiaries also purchased $24 million face amount of senior debt and subordinate tranches of existing CLOs for $17 million . During 2016 , AFG subsidiaries also received $115 million in sale and redemption proceeds from its CLO investments. In 2015 , AFG formed two new CLOs, which issued an aggregate of $869 million face amount of liabilities (including $81 million face amount purchased by subsidiaries of AFG). In 2017, two AFG CLOs were substantially liquidated, as permitted by the CLO indentures. The revenues and expenses of the CLOs are separately identified in AFG’s Statement of Earnings, after the elimination of management fees and earnings attributable to shareholders of AFG as measured by the change in the fair value of AFG’s investments in the CLOs. Selected financial information related to the CLOs is shown below (in millions): Year ended December 31, 2017 2016 2015 Investment in CLO tranches $ 215 $ 216 $ 266 Gains (losses) on change in fair value of assets/liabilities (a): Assets (8 ) 131 (116 ) Liabilities 20 (116 ) 82 Management fees paid to AFG 18 17 15 CLO earnings (losses) attributable to AFG Shareholders (b) 23 37 (6 ) (a) Included in revenues in AFG’s Statement of Earnings. (b) Included in earnings before income taxes in AFG’s Statement of Earnings. The aggregate unpaid principal balance of the CLOs’ fixed maturity investments exceeded the fair value of the investments by $55 million and $75 million at December 31, 2017 and 2016 . The aggregate unpaid principal balance of the CLOs’ debt exceeded its carrying value by $118 million and $159 million at those dates. The CLO assets include loans with an aggregate fair value of $1 million at both December 31, 2017 and December 31, 2016 , for which the CLOs are not accruing interest because the loans are in default (aggregate unpaid principal balance of $8 million and $10 million at those dates, respectively).

Goodwill and Other Intangibles

Goodwill and Other Intangibles	12 Months Ended
	Dec. 31, 2017
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill and Other Intangibles	Goodwill and Other Intangibles Changes in the carrying value of goodwill during 2015 , 2016 and 2017 , by reporting segment, are presented in the following table (in millions): Property and Casualty Annuity Total Balance at January 1, 2015 $ 168 $ 33 $ 201 Sale of subsidiaries in 2015 — (2 ) (2 ) Balance at December 31, 2015, December 31, 2016 and December 31, 2017 $ 168 $ 31 $ 199 Goodwill decreased by $2 million in the fourth quarter of 2015 due to the sale of UTA and CGIC as discussed in Note B — “ Acquisitions and Sale of Businesses .” Included in other assets in AFG’s Balance Sheet is $26 million at December 31, 2017 and $34 million at December 31, 2016 of amortizable intangible assets related to property and casualty insurance acquisitions. These amounts are net of accumulated amortization of $30 million and $25 million , respectively. Amortization of intangibles was $8 million in each of 2017 , 2016 and 2015 . Future amortization of intangibles (weighted average amortization period of 3 years ) is estimated to be $8 million per year in each of 2018 through 2020 and $2 million in 2021.

Long-Term Debt

Long-Term Debt	12 Months Ended
	Dec. 31, 2017
Debt Disclosure [Abstract]
Long-Term Debt	Long-Term Debt Long-term debt consisted of the following at December 31 (in millions): 2017 2016 Principal Discount and Issue Costs Carrying Value Principal Discount and Issue Costs Carrying Value Direct Senior Obligations of AFG: 4.50% Senior Notes due June 2047 $ 590 $ (2 ) $ 588 $ — $ — $ — 3.50% Senior Notes due August 2026 425 (5 ) 420 300 (3 ) 297 9-7/8% Senior Notes due June 2019 — — — 350 (1 ) 349 6-3/8% Senior Notes due June 2042 — — — 230 (7 ) 223 5-3/4% Senior Notes due August 2042 — — — 125 (4 ) 121 Other 3 — 3 3 — 3 1,018 (7 ) 1,011 1,008 (15 ) 993 Direct Subordinated Obligations of AFG: 6-1/4% Subordinated Debentures due September 2054 150 (5 ) 145 150 (5 ) 145 6% Subordinated Debentures due November 2055 150 (5 ) 145 150 (5 ) 145 300 (10 ) 290 300 (10 ) 290 $ 1,318 $ (17 ) $ 1,301 $ 1,308 $ (25 ) $ 1,283 At December 31, 2017 , scheduled principal payments on debt for the subsequent five years and thereafter were as follows: 2018 — none ; 2019 — none ; 2020 — none ; 2021 — none ; 2022 — none and thereafter — $1.32 billion . In June 2017, AFG issued $350 million in 4.50% Senior Notes due in 2047 at a price of 99.46% . The net proceeds of the offering were used to redeem AFG’s $230 million outstanding principal amount of 6-3/8% Senior Notes due June 2042 at par value and to redeem AFG’s $125 million outstanding principal amount of 5-3/4% Senior Notes due August 2042 at par value in June 2017 and August 2017, respectively. In November 2017, AFG issued an additional $125 million of 3.50% Senior Notes due in 2026 at a price of 99.698% and $240 million of 4.50% Senior Notes due in 2047 at a price of 102.374% . The net proceeds of the offering were used to redeem AFG’s $350 million outstanding principal amount of 9-7/8% Senior Notes due in June 2019 for $388 million (including a make-whole premium of $38 million ) in December 2017. In August 2016, AFG issued $300 million in 3.50% Senior Notes due in 2026 at a price of 99.608% . The net proceeds of the offering were used to fund a portion of the November 2016 acquisition of the noncontrolling interest in NATL (discussed in Note B — “ Acquisitions and Sale of Businesses ” ). At the acquisition date, the $18 million outstanding under NATL’s bank credit facility, including $6 million borrowed in September 2016, was repaid and the credit agreement was terminated. In September 2015, AFG used cash on hand to redeem the $132 million in outstanding AFG 7% Senior Notes due September 2050 at par value. In November 2015, AFG issued $150 million in 6% Subordinated Debentures due in 2055. During 2015, subsidiaries of AFG repaid all of the outstanding notes secured by real estate. To achieve a desired balance between fixed and variable rate debt, AFG entered into an interest rate swap in June 2015, which effectively converted its 9-7/8% Senior Notes to a floating rate of three-month LIBOR plus 8.099% . In December 2017, AFG settled the interest rate swap contemporaneously with the redemption of the 9-7/8% Senior Notes. At December 31, 2016, the fair value of the interest rate swap (asset of $1 million at that date) and the offsetting adjustment to the carrying value of the notes were both included in the carrying value of the 9-7/8% Senior Notes in the table above. AFG can borrow up to $500 million under its revolving credit facility, which expires in June 2021. Amounts borrowed under this agreement bear interest at rates ranging from 1.00% to 1.875% (currently 1.375% ) over LIBOR based on AFG’s credit rating. No amounts were borrowed under this facility at December 31, 2017 or December 31, 2016 . Cash interest payments on long-term debt were $85 million in 2017 , $75 million in 2016 and 2015 . In 2017 , 2016 and 2015 , AFG received $2 million , $3 million and $2 million , respectively, in interest under the interest rate swap discussed above.

Shareholders' Equity

Shareholders' Equity	12 Months Ended
	Dec. 31, 2017
Stockholders' Equity Note [Abstract]
Shareholders' Equity	Shareholders’ Equity AFG is authorized to issue 12.5 million shares of Voting Preferred Stock and 12.5 million shares of Nonvoting Preferred Stock, each without par value. Stock Incentive Plans Under AFG’s stock incentive plans, employees of AFG and its subsidiaries are eligible to receive equity awards in the form of stock options, stock appreciation rights, restricted stock awards, restricted stock units and stock awards. At December 31, 2017 , there were 8.0 million shares of AFG Common Stock reserved for issuance under AFG’s stock incentive plans. The restricted Common Stock that AFG has granted generally vests over a three or four year period. Data relating to grants of restricted stock is presented below: Shares Average Grant Date Fair Value Outstanding at January 1, 2017 678,875 $ 60.90 Granted 232,250 $ 94.44 Vested (145,473 ) $ 48.76 Forfeited (6,617 ) $ 71.30 Outstanding at December 31, 2017 759,035 $ 73.40 AFG issued 47,826 shares of Common Stock (fair value of $96.13 per share) in the first quarter of 2017 and 40,336 shares (fair value of $71.05 per share) in the first quarter of 2016 under its Equity Bonus Plan. AFG did not grant any stock options in 2017 or 2016. Options granted in years prior to 2016 have an exercise price equal to the market price of AFG Common Stock at the date of grant. Options generally become exercisable at the rate of 20% per year commencing one year after grant and expire ten years after the date of grant. Data for stock options issued under AFG’s stock incentive plans is presented below: Shares Average Exercise Price Average Remaining Contractual Term Aggregate Intrinsic Value (in millions) Outstanding at January 1, 2017 4,505,101 $ 43.02 Exercised (1,020,986 ) $ 33.38 Forfeited/Cancelled (16,775 ) $ 55.82 Outstanding at December 31, 2017 3,467,340 $ 45.80 4.9 years $ 218 Options exercisable at December 31, 2017 2,589,277 $ 42.00 4.4 years $ 172 The total intrinsic value of options exercised during 2017 , 2016 and 2015 was $65 million , $38 million and $52 million , respectively. During 2017 , 2016 and 2015 , AFG received $33 million , $32 million and $47 million , respectively, in cash from the exercise of stock options. The total tax benefit related to the exercises was $18 million , $11 million and $16 million (including $12 million credited directly to capital surplus in 2015) during those years, respectively. AFG used the Black-Scholes option pricing model to calculate the fair value of its option grants issued during 2015 ( no options were granted in 2016 or 2017). The expected dividend yield is based on AFG’s current dividend rate. To determine expected volatility, AFG considers its daily historical volatility as well as implied volatility on traded options. The expected term was estimated based on historical exercise patterns and post vesting cancellations. The risk-free rate for periods associated with the expected term is based upon the U.S. Treasury yield curve in effect on the grant date. 2015 Exercise price $ 63.15 Expected dividend yield 1.6 % Expected volatility 25 % Expected term (in years) 7.25 Risk-free rate 1.88 % Grant date fair value $ 15.29 Total compensation expense related to stock incentive plans of AFG and its subsidiaries for 2017 , 2016 and 2015 was $30 million , $28 million and $27 million , respectively. AFG’s provision for income tax includes tax benefits of $27 million in 2017 , $19 million in 2016 and $8 million in 2015 related to AFG’s stock incentive plans. The tax benefit of $27 million in 2017 and $19 million in 2016 includes $17 million and $9 million , respectively, that under the previous guidance would have been recorded directly to capital surplus. At December 31, 2017 , there was $7 million and $31 million of unrecognized compensation expense related to nonvested stock options and restricted stock awards, respectively. The nonvested stock options and restricted stock awards amounts are expected to be recognized over a weighted average of 1.7 years and 2.6 years, respectively. Accumulated Other Comprehensive Income, Net of Tax (“AOCI”) Comprehensive income is defined as all changes in shareholders’ equity except those arising from transactions with shareholders. Comprehensive income includes net earnings and other comprehensive income, which consists primarily of changes in net unrealized gains or losses on available for sale securities. The progression of the components of accumulated other comprehensive income follows (in millions): Other Comprehensive Income AOCI Beginning Balance Pretax Tax Net of tax Attributable to noncontrolling interests Attributable to shareholders Other (c) AOCI Ending Balance Year ended December 31, 2017 Net unrealized gains on securities: Unrealized holding gains on securities arising during the period $ 456 $ (159 ) $ 297 $ — $ 297 Reclassification adjustment for realized (gains) losses included in net earnings (a) (15 ) 5 (10 ) — (10 ) Total net unrealized gains on securities (b) $ 404 441 (154 ) 287 — 287 $ 149 $ 840 Net unrealized losses on cash flow hedges (7 ) (6 ) 2 (4 ) — (4 ) (2 ) (13 ) Foreign currency translation adjustments (15 ) 9 3 12 — 12 (3 ) (6 ) Pension and other postretirement plans adjustments (7 ) 1 — 1 — 1 (2 ) (8 ) Total $ 375 $ 445 $ (149 ) $ 296 $ — $ 296 $ 142 $ 813 Year ended December 31, 2016 Net unrealized gains on securities: Unrealized holding gains on securities arising during the period $ 124 $ (44 ) $ 80 $ (4 ) $ 76 Reclassification adjustment for realized (gains) losses included in net earnings (a) (19 ) 7 (12 ) (1 ) (13 ) Total net unrealized gains on securities (b) $ 332 105 (37 ) 68 (5 ) 63 $ 9 $ 404 Net unrealized gains (losses) on cash flow hedges 1 (12 ) 4 (8 ) — (8 ) — (7 ) Foreign currency translation adjustments (22 ) 6 1 7 — 7 — (15 ) Pension and other postretirement plans adjustments (7 ) — — — — — — (7 ) Total $ 304 $ 99 $ (32 ) $ 67 $ (5 ) $ 62 $ 9 $ 375 Year ended December 31, 2015 Net unrealized gains (losses) on securities: Unrealized holding losses on securities arising during the period $ (625 ) $ 219 $ (406 ) $ 9 $ (397 ) Reclassification adjustment for realized (gains) losses included in net earnings (a) 14 (5 ) 9 (1 ) 8 Reclassification for unrealized gains of subsidiaries sold (34 ) 12 (22 ) — (22 ) Total net unrealized gains (losses) on securities (b) $ 743 (645 ) 226 (419 ) 8 (411 ) $ — $ 332 Net unrealized gains on cash flow hedges — 1 — 1 — 1 — 1 Foreign currency translation adjustments (8 ) (9 ) (5 ) (14 ) — (14 ) — (22 ) Pension and other postretirement plans adjustments (8 ) 1 — 1 — 1 — (7 ) Total $ 727 $ (652 ) $ 221 $ (431 ) $ 8 $ (423 ) $ — $ 304 (a) The reclassification adjustment out of net unrealized gains on securities affected the following lines in AFG’s Statement of Earnings: OCI component Affected line in the statement of earnings Pretax Realized gains (losses) on securities Tax Provision for income taxes Attributable to noncontrolling interests Net earnings attributable to noncontrolling interests (b) Includes net unrealized gains of $68 million at December 31, 2017 compared to net unrealized gains of $52 million and $51 million at December 31, 2016 and 2015 , related to securities for which only the credit portion of an other-than-temporary impairment has been recorded in earnings. (c) Other includes the December 2017 reclassification of $145 million stranded in AOCI from accounting for the Tax Cuts and Jobs Act of 2017 to retained earnings (see Note A — “ Accounting Policies — Income Taxes ”) , and the impact on AOCI of the December 2017 sale of redeemable noncontrolling interests in Neon and the November 2016 acquisition of the noncontrolling interest in NATL (see Note B — “ Acquisitions and Sale of Businesses ”).

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes The following is a reconciliation of income taxes at the statutory rate of 35% to the provision for income taxes as shown in AFG’s Statement of Earnings (dollars in millions): 2017 2016 2015 Amount % of EBT Amount % of EBT Amount % of EBT Earnings before income taxes (“EBT”) $ 724 $ 787 $ 565 Income taxes at statutory rate $ 253 35 % $ 275 35 % $ 198 35 % Effect of: Tax exempt interest (23 ) (3 %) (24 ) (3 %) (27 ) (5 %) Dividend received deduction (8 ) (1 %) (7 ) (1 %) (8 ) (1 %) Stock-based compensation (16 ) (2 %) (9 ) (1 %) 1 — % Employee stock ownership plan dividend paid deduction (5 ) (1 %) (2 ) — % (1 ) — % Foreign operations 21 3 % 5 — % 3 1 % Change in valuation allowance (excluding change in tax rate) (7 ) (1 %) 52 7 % 23 4 % Subsidiaries not in AFG’s tax return — — % 3 — % 2 — % Neon restructuring (56 ) (8 %) (111 ) (14 %) — — % Change in U.S corporate tax rate 83 11 % — — % — — % Acquisition of noncontrolling interest in NATL — — % (66 ) (8 %) — — % Other 5 1 % 3 — % 4 1 % Provision for income taxes as shown in the statement of earnings $ 247 34 % $ 119 15 % $ 195 35 % The favorable impact of stock-based compensation on AFG’s effective tax rate in the year ended December 31, 2017 reflects the high volume of employee stock option exercises during that period and the increase in the market price of AFG Common Stock. In January 2008, AFG paid $75 million in cash to acquire approximately 67% of Neon Underwriting Limited (“Neon”, formerly known as Marketform Group Limited), a United Kingdom-based Lloyd’s insurer. During 2012, AFG acquired the then-remaining shares of Neon that it did not already own for $17 million . AFG’s investment in Neon includes the cost of acquiring the company as well as additional capital provided to Neon since the date of acquisition. In 2011, cumulative losses at Neon across multiple lines of business resulted in uncertainty concerning the realization of the deferred tax benefits associated with the losses. Consequently, AFG began maintaining a full valuation allowance against the deferred tax assets related to the Lloyd’s insurance business in 2011. Approximately $14 million of the $21 million impact of “foreign operations” for 2017 in the table above relates to a reduction in the “foreign underwriting losses” deferred tax asset as a result of the sale of the noncontrolling interest in Neon. Since AFG maintains a full valuation allowance against the deferred tax assets related to Neon, this reduction in deferred tax assets was offset by a corresponding reduction in the valuation allowance and had no overall impact on AFG’s income tax expense or results of operations. The changes in valuation allowance in the table above are primarily increases in the valuation allowance on tax benefits related to losses in the Neon Lloyd’s insurance business. The $61 million decrease in the valuation allowance related to the change in the U.S. corporate tax rate is included in “Change in U.S. corporate tax rate” in table above. In connection with the reorganization of the Neon Lloyd’s business, in December 2016, AFG undertook a restructuring that included the liquidation for tax purposes of the foreign subsidiary that is the parent of the Neon Lloyd’s operations, resulting in a taxable loss for U.S. tax purposes. AFG reported a $111 million tax benefit associated with this loss in the fourth quarter of 2016. Approximately $29 million of the $111 million tax benefit recorded in 2016 reduced current taxes payable for 2016, while the remaining tax benefit was received in 2017 from the carry-back of the tax-basis capital loss to offset capital gains in prior years. An additional loss associated with the 2016 restructuring was deferred under U.S. tax laws, resulting in an unrecognized potential tax benefit of $48 million at December 31, 2016 . The sale of the noncontrolling interest in Neon resulted in the recognition of an additional tax benefit of $56 million in the fourth quarter of 2017, including the recognition of the deferred loss from the 2016 restructuring. Approximately $20 million of the $56 million tax benefit recorded in 2017 reduced current taxes payable for 2017, while the majority of the remaining tax benefit will be received in 2018 from the carry-back of the tax basis capital loss to offset capital gains in prior years. The Tax Cuts and Jobs Act of 2017 (“TCJA”), which lowers the U.S corporate tax rate to 21% and makes other widespread changes to the U.S. tax code beginning in 2018, was enacted on December 22, 2017. Because the TCJA was enacted in December 2017, AFG recorded the $83 million decrease in its net deferred tax asset resulting from the changes in the tax code (primarily the lower corporate tax rate applicable to 2018 and future years) in the fourth quarter of 2017. The TCJA is subject to further clarification and interpretation by the U.S. Treasury Department and the Internal Revenue Service. For example, the TCJA changes the way that companies calculate their insurance claims and reserves for tax purposes, including revaluing those tax basis liabilities as of January 1, 2018, based on a methodology and discount factors that have not been published. The resulting transitional deferred tax liability (taxes payable over eight years under the TCJA) and offsetting increase in AFG’s insurance claims and reserves deferred tax assets, were recorded at December 31, 2017 using reasonable estimates based on available information and should be considered provisional in accordance with Securities and Exchange Commission Staff Accounting Bulletin No. 118 (“SAB 118”). Because the established transition liability was completely offset by an increase in related deferred tax assets, any adjustment to the provisional amount will not impact AFG’s effective tax rate. In accordance with SAB 118, the insurance claims and reserves transitional deferred tax liability (and offsetting adjustment to the related deferred tax assets) and any other changes in deferred taxes resulting from clarification and interpretation of the TCJA provided during 2018 will be recorded in the period in which the guidance is published. As discussed in Note B — “ Acquisitions and Sale of Businesses ,” AFG acquired the noncontrolling interest in NATL in November 2016. This transaction allowed NATL and its subsidiaries to become members of the AFG consolidated tax group, which resulted in a tax benefit of $66 million to AFG during the fourth quarter of 2016. Excluding the tax benefit related to the Neon restructuring and the impact of the change in the U.S. corporate tax rate, AFG’s effective tax rate for the year ended December 31, 2017 was 31% . Excluding a $65 million charge related to the exit of certain lines of business within Neon and the tax benefits related to the acquisition of the noncontrolling interest in NATL and the Neon restructuring, AFG’s effective tax rate for the year ended December 31, 2016 was 35% . AFG’s 2012 — 2017 tax years remain subject to examination by the IRS. Total earnings before income taxes include losses subject to tax in foreign jurisdictions of $58 million in 2017 , $160 million in 2016 and $66 million in 2015 , primarily related to the Neon Lloyd’s operations. The total income tax provision (credit) consists of (in millions): 2017 2016 2015 Current taxes: Federal $ 153 $ 299 $ 216 State 6 12 8 Deferred taxes: Federal 5 (192 ) (29 ) Impact of change in U.S. corporate tax rate 83 — — Total Federal deferred taxes 88 (192 ) (29 ) Provision for income taxes $ 247 $ 119 $ 195 For income tax purposes, AFG and its subsidiaries had the following carryforwards available at December 31, 2017 (in millions): Expiring Amount Operating Loss – U.S. 2018 - 2022 $ 130 Operating Loss – United Kingdom indefinite 252 (*) Capital Loss – U.S. 2022 109 (*) £186 million Deferred income tax assets and liabilities reflect temporary differences between the carrying amounts of assets and liabilities recognized for financial reporting purposes and the amounts recognized for tax purposes. The significant components of deferred tax assets and liabilities included in AFG’s Balance Sheet at December 31 were as follows (in millions): 2017 2016 Excluding Unrealized Gains Impact of Unrealized Gains Total Excluding Unrealized Gains Impact of Unrealized Gains Total Deferred tax assets: Federal net operating loss carryforwards $ 27 $ — $ 27 $ 50 $ — $ 50 Foreign underwriting losses 80 — 80 120 — 120 Capital loss carryforwards 32 — 32 83 — 83 Insurance claims and reserves 665 29 694 774 27 801 Employee benefits 84 — 84 131 — 131 Other, net 48 (3 ) 45 85 (5 ) 80 Total deferred tax assets before valuation allowance 936 26 962 1,243 22 1,265 Valuation allowance against deferred tax assets (109 ) — (109 ) (173 ) — (173 ) Total deferred tax assets 827 26 853 1,070 22 1,092 Deferred tax liabilities: Investment securities (1 ) (340 ) (341 ) 29 (336 ) (307 ) Deferred policy acquisition costs (293 ) 91 (202 ) (448 ) 96 (352 ) Insurance claims and reserves transition liability (128 ) — (128 ) — — — Real estate, property and equipment (35 ) — (35 ) (45 ) — (45 ) Total deferred tax liabilities (457 ) (249 ) (706 ) (464 ) (240 ) (704 ) Net deferred tax asset (liability) $ 370 $ (223 ) $ 147 $ 606 $ (218 ) $ 388 AFG’s net deferred tax asset at December 31, 2017 and 2016 is included in other assets in AFG’s Balance Sheet. The decrease in AFG’s net deferred tax asset at December 31, 2017 compared to December 31, 2016 reflects the impact of the change in the U.S. corporate tax rate, partially offset by higher pretax unrealized gains on securities. The likelihood of realizing deferred tax assets is reviewed periodically; any adjustments required to the valuation allowance are made in the period during which developments requiring an adjustment become known. “Foreign underwriting losses” in the table above include the net operating loss carryforward and other deferred tax assets related to the Neon Lloyd’s insurance business. Due to uncertainty concerning the realization of the deferred tax benefits associated with these losses, AFG maintains a full valuation allowance of $80 million against these deferred tax assets at December 31, 2017 . In addition to the valuation allowance related to the Neon Lloyd’s insurance business, the gross deferred tax asset has also been reduced by a $27 million valuation allowance related to AFG’s net operating loss carryforwards (“NOL”) subject to the separate return limitation year (“SRLY”) tax rules. A SRLY NOL can be used only by the entity that created it and only in years that both it and the consolidated group have taxable income. Approximately $13 million of AFG’s SRLY NOLs expired unutilized at December 31, 2017. Since AFG maintains a full valuation allowance against its SRLY NOLs, the expiration of these loss carryforwards was offset by corresponding reduction in the valuation allowance and had no overall impact on AFG’s income tax expense or results of operations. AFG increased its liability for uncertain tax positions by $1 million in 2015 due to uncertainty in state taxation of its surplus lines insurance subsidiaries. In 2017, this uncertainty was resolved, resulting in total tax payments of less than $1 million . A progression of the liability for uncertain tax positions, excluding interest and penalties, follows (in millions): 2017 2016 2015 Balance at January 1 $ 1 $ 1 $ — Additions for tax positions of prior years — — 1 Reductions for tax positions of prior years — — — Additions for tax positions of current year — — — Settlements (1 ) — — Balance at December 31 $ — $ 1 $ 1 The total unrecognized tax benefits and related interest and penalties that, if recognized, would impact the effective tax rate is less than $1 million at December 31, 2017 and December 31, 2016 . AFG’s provision for income taxes included a benefit of less than $1 million in 2017 and an expense of less than $1 million in 2016 and 2015 of interest (net of federal benefit or expense). AFG’s liability for interest related to unrecognized tax benefits was less than $1 million at December 31, 2017 and December 31, 2016 (net of federal benefit). AFG’s provision for income taxes in 2017 and 2016 included penalties of less than $1 million ; no penalties were recorded in 2015 . AFG’s liability for penalties related to unrecognized tax benefits was less than $1 million at December 31, 2017 and December 31, 2016 . Cash payments for income taxes, net of refunds, were $194 million , $308 million and $234 million for 2017 , 2016 and 2015 , respectively.

Contingencies

Contingencies	12 Months Ended
	Dec. 31, 2017
Commitments and Contingencies Disclosure [Abstract]
Contingencies	Contingencies Establishing property and casualty insurance reserves for claims related to environmental exposures, asbestos and other mass tort claims is subject to uncertainties that are significantly greater than those presented by other types of claims. For this group of claims, traditional actuarial techniques that rely on historical loss development trends cannot be used and a range of reasonably possible losses cannot be estimated. In addition, accruals (included in other liabilities) have been recorded for various environmental and occupational injury and disease claims and other contingencies arising out of the railroad operations disposed of by American Premier’s predecessor, Penn Central Transportation Company (“PCTC”) and its subsidiaries, prior to its bankruptcy reorganization in 1978 and certain manufacturing operations disposed of by American Premier and Great American Financial Resources, Inc. (“GAFRI”). AFG completed a comprehensive external study of its asbestos and environmental (“A&E”) exposures in the third quarter of 2017 with the aid of specialty actuarial, engineering and consulting firms and outside counsel. The study resulted in special A&E charges of $89 million for the property and casualty group and $24 million for the former railroad and manufacturing operations. AFG completed an in-depth internal review of its A&E exposures in the third quarter of 2016. The review resulted in special A&E charges of $36 million for the property and casualty group and $5 million for the former railroad and manufacturing operations. AFG completed a comprehensive external study of its A&E exposures in the third quarter of 2015 with the aid of specialty actuarial, engineering and consulting firms and outside counsel. The study resulted in special A&E charges of $67 million for the property and casualty group and $12 million for the former railroad and manufacturing operations. The property and casualty group’s liability for A&E reserves was $528 million at December 31, 2017 ; related recoverables from reinsurers (net of allowances for doubtful accounts) at that date were $125 million . At December 31, 2017 , American Premier and its subsidiaries had liabilities for environmental and personal injury claims and other contingencies aggregating $81 million . The environmental claims consist of a number of proceedings and claims seeking to impose responsibility for hazardous waste remediation costs related to certain sites formerly owned or operated by the railroad and manufacturing operations. Remediation costs are difficult to estimate for a number of reasons, including the number and financial resources of other potentially responsible parties, the range of costs for remediation alternatives, changing technology and the time period over which these matters develop. The personal injury claims and other contingencies include pending and expected claims, primarily by former employees of PCTC, for injury or disease allegedly caused by exposure to excessive noise, asbestos or other substances in the workplace and other labor disputes. At December 31, 2017 , GAFRI had a liability of $8 million for environmental costs and certain other matters associated with the sales of its former manufacturing operations. See Note B — “ Acquisitions and Sale of Businesses ” for a discussion of the five -year capital maintenance agreement that AFG entered into in connection with obtaining regulatory approval for the sale of substantially all of its run-off long-term care insurance business in December 2015. While management believes AFG has recorded adequate reserves for the items discussed above, the outcome is uncertain and could result in liabilities that may vary from amounts AFG has currently recorded. Such amounts could have a material effect on AFG’s future results of operations and financial condition. In addition, AFG and its subsidiaries are involved in litigation from time to time, generally arising in the ordinary course of business. This litigation may include, but is not limited to, general commercial disputes, lawsuits brought by policyholders, employment matters, reinsurance collection matters and actions challenging certain business practices of insurance subsidiaries. None of these matters are expected to have a material adverse impact on AFG’s results of operations or financial condition.

Quarterly Operating Results (Un

Quarterly Operating Results (Unaudited)	12 Months Ended
	Dec. 31, 2017
Quarterly Financial Information Disclosure [Abstract]
Quarterly Operating Results (Unaudited)	Quarterly Operating Results (Unaudited) The operations of certain AFG business segments are seasonal in nature. While insurance premiums are recognized on a relatively level basis, claim losses related to adverse weather (snow, hail, hurricanes, severe storms, tornadoes, etc.) may be seasonal. The profitability of AFG’s crop insurance business is primarily recognized during the second half of the year as crop prices and yields are determined. Quarterly results necessarily rely heavily on estimates. These estimates and certain other factors, such as the discretionary sales of assets, cause the quarterly results not to be necessarily indicative of results for longer periods of time. The following are quarterly results of consolidated operations for the two years ended December 31, 2017 (in millions, except per share amounts). Quarterly earnings per share do not add to year-to-date amounts due to changes in shares outstanding. 1st Quarter 2nd Quarter 3rd Quarter 4th Quarter Total Year 2017 Revenues $ 1,576 $ 1,646 $ 1,835 $ 1,808 $ 6,865 Net earnings, including noncontrolling interests 155 145 11 166 477 Net earnings attributable to shareholders 153 145 11 166 475 Earnings attributable to shareholders per Common Share: Basic $ 1.76 $ 1.64 $ 0.13 $ 1.88 $ 5.40 Diluted 1.72 1.61 0.13 1.84 5.28 Average number of Common Shares: Basic 87.2 87.8 88.1 88.2 87.8 Diluted 89.3 89.8 90.0 90.1 89.8 2016 Revenues $ 1,475 $ 1,581 $ 1,705 $ 1,737 $ 6,498 Net earnings, including noncontrolling interests 104 63 113 388 668 Net earnings attributable to shareholders 101 54 109 385 649 Earnings attributable to shareholders per Common Share: Basic $ 1.16 $ 0.63 $ 1.25 $ 4.43 $ 7.47 Diluted 1.14 0.62 1.23 4.33 7.33 Average number of Common Shares: Basic 86.9 86.8 86.9 86.9 86.9 Diluted 88.5 88.4 88.5 88.8 88.5 Pretax realized gains on subsidiaries and securities (including other-than-temporary impairments), favorable (adverse) prior year development of AFG’s liability for losses and loss adjustment expenses (“LAE”) and the impact of derivatives related to FIAs were as follows (in millions): 1st Quarter 2nd Quarter 3rd Quarter 4th Quarter Total Year Realized Gains (Losses) on Securities and Subsidiaries 2017 $ 3 $ 8 $ (12 ) $ 6 $ 5 2016 (18 ) (14 ) 2 51 21 Prior Year Development Favorable (Adverse) 2017 $ 28 $ 22 $ (52 ) $ 66 $ 64 2016 28 (28 ) (22 ) (10 ) (32 ) Impact of Derivatives related to Fixed-indexed Annuities 2017 $ (2 ) $ (16 ) $ (4 ) $ (11 ) $ (33 ) 2016 (31 ) (26 ) 1 29 (27 ) Adverse prior year development for the third quarters of 2017 and 2016 include pretax special charges of $89 million and $36 million , respectively, to strengthen property and casualty insurance A&E reserves. As a result of the Neon reinsurance to close agreement discussed in Note O — “ Insurance ,” Neon recorded $42 million in favorable development in the fourth quarter of 2017 , of which $24 million related to its ongoing lines of business and $18 million related to its exited lines of business. During the second quarter of 2016 , AFG recorded a pretax charge of $65 million related to Neon’s claims review of its exited lines of business, including $57 million to increase loss reserves primarily related to its medical malpractice and general liability classes. Fixed-indexed annuities (“FIAs”) provide policyholders with a crediting rate tied, in part, to the performance of an existing stock market or other financial index. AFG attempts to mitigate the risk in the index-based component of these products through the purchase of call options on the appropriate index. AFG’s strategy is designed so that the change in the fair value of the call option assets will generally offset the economic change in the liabilities from the index participation. Both the index-based component of the annuities and the related call options are considered derivatives that must be marked-to-market through earnings each period. Fluctuations in interest rates and the stock market, among other factors, can cause volatility in the periodic measurement of fair value of the embedded derivative that management believes can be inconsistent with the long-term economics of these products. In the table above, the impact of changes in the fair value of the derivatives related to FIAs is presented net of an estimate of the related acceleration/deceleration of the amortization of deferred policy acquisition costs and deferred sales inducements. AFG’s property and casualty operations recorded catastrophe losses totaling $140 million in 2017 , including $107 million in the third quarter (primarily from Hurricanes Harvey, Irma and Maria and earthquakes in Mexico). Catastrophe losses for 2016 totaling $55 million were spread somewhat evenly across the four quarters. Results include pretax gains (included in other income) of $13 million from the sale of a hotel in the first quarter of 2017 and $32 million from the sale of an apartment property in the second quarter of 2016. Results for the third quarter of 2017 and 2016 include pretax special charges of $24 million and $5 million , respectively, to strengthen reserves for A&E exposures related to AFG’s former railroad and manufacturing operations. In 2017, AFG recorded pretax losses on the retirement of debt of $7 million in the second quarter, $4 million in the third quarter and $40 million in the fourth quarter. Net earnings in the fourth quarter of 2017 includes $56 million in tax benefits related to the Neon restructuring. Net earnings in the fourth quarter of 2016 includes $177 million in tax benefits related to the NATL merger and Neon restructuring. See Note L — “ Income Taxes .”

Insurance

Insurance	12 Months Ended
	Dec. 31, 2017
Insurance [Abstract]
Insurance	Insurance Cash and securities owned by U.S.-based insurance subsidiaries, having a carrying value of approximately $1.08 billion at December 31, 2017 , were on deposit as required by regulatory authorities. In addition, $205 million was on deposit in support of AFG’s underwriting activities at Lloyd’s. At December 31, 2017 , AFG and its subsidiaries had $447 million in undrawn letters of credit ( none of which was collateralized) supporting the underwriting capacity of its U.K.-based Lloyd’s insurer, Neon. Property and Casualty Insurance Reserves Estimating the liability for unpaid losses and loss adjustment expenses (“LAE”) is inherently judgmental and is influenced by factors that are subject to significant variation. Determining the liability is a complex process incorporating input from many areas of the Company including actuarial, underwriting, pricing, claims and operations management. The process used to determine the total reserve for liabilities involves estimating the ultimate incurred losses and LAE, adjusted for amounts already paid on the claims. The IBNR reserve is derived by first estimating the ultimate unpaid reserve liability and subtracting case reserves for loss and LAE. In determining management’s best estimate of the ultimate liability, management (with the assistance of Company actuaries) considers items such as the effect of inflation on medical, hospitalization, material, repair and replacement costs, the nature and maturity of lines of insurance, general economic trends and the legal environment. In addition, historical trends adjusted for changes in underwriting standards, policy provisions, product mix and other factors are analyzed using actuarial reserve development techniques. Weighing all of the factors, the management team determines a single or “point” estimate that it records as its best estimate of the ultimate liability. Ranges of loss reserves are not developed by Company actuaries. This reserve analysis and review is completed each quarter and for almost every business within AFG’s property and casualty insurance sub-segments. Each review includes in-depth analysis of several hundred subdivisions of the business, employing multiple actuarial techniques. For each subdivision, actuaries use informed, professional judgment to adjust these techniques as necessary to respond to specific conditions in the data or within the business. Some of the standard actuarial methods employed for the quarterly reserve analysis may include (but may not be limited to): • Case Incurred Development Method • Paid Development Method • Bornhuetter-Ferguson Method • Incremental Paid LAE to Paid Loss Methods Management believes that each method has particular strengths and weaknesses and that no single estimation method is most accurate in all situations. When applied to a particular group of claims, the relative strengths and weaknesses of each method can change over time based on the facts and circumstances. Ultimately, the estimation methods chosen are those which management believes produce the most reliable indication for the particular liabilities under review. The period of time from the occurrence of a loss through the settlement of the liability is referred to as the “tail”. Generally, the same actuarial methods are considered for both short-tail and long-tail lines of business because most of them work properly for both. The methods are designed to incorporate the effects of the differing length of time to settle particular claims. For short-tail lines, management tends to give more weight to the Case Incurred and Paid Development methods, although the various methods tend to produce similar results. For long-tail lines, more judgment is involved, and more weight may be given to the Bornhuetter-Ferguson method. Liability claims for long-tail lines are more susceptible to litigation and can be significantly affected by changing contract interpretation and the legal environment. Therefore, the estimation of loss reserves for these classes is more complex and subject to a higher degree of variability. The level of detail in which data is analyzed varies among the different lines of business. Data is generally analyzed by major product or by coverage within product, using countrywide data; however, in some situations, data may be reviewed by state or region. Appropriate segmentation of the data is determined based on data credibility, homogeneity of development patterns, mix of business, and other actuarial considerations. Supplementary statistical information is also reviewed to determine which methods are most appropriate to use or if adjustments are needed to particular methods. Such information includes: • Open and closed claim counts • Average case reserves and average incurred on open claims • Closure rates and statistics related to closed and open claim percentages • Average closed claim severity • Ultimate claim severity • Reported loss ratios • Projected ultimate loss ratios • Loss payment patterns Within each business, results of individual methods are reviewed, supplementary statistical information is analyzed, and data from underwriting, operating and claim management are considered in deriving management’s best estimate of the ultimate liability. This estimate may be the result of one method, a weighted average of several methods, or a judgmental selection as the management team determines is appropriate. The liability for losses and LAE for a very limited number of claims with long-term scheduled payments under certain workers’ compensation policies has been discounted at 4.5% at both December 31, 2017 and 2016 , which represents an approximation of long-term investment yields. Because of the limited amount of claims involved, the net impact of discounting did not materially impact AFG’s total liability for unpaid losses and loss adjustment expenses (net reductions from discounting of $15 million and $16 million at December 31, 2017 and 2016 , respectively). The following table provides an analysis of changes in the liability for losses and loss adjustment expenses over the past three years (in millions): 2017 2016 2015 Balance at beginning of period $ 8,563 $ 8,127 $ 7,872 Less reinsurance recoverables, net of allowance 2,302 2,201 2,227 Net liability at beginning of period 6,261 5,926 5,645 Provision for losses and LAE occurring in the current year 3,019 2,730 2,662 Net increase (decrease) in the provision for claims of prior years: Special A&E charges 89 36 67 Neon exited lines charge (18 ) 57 — Other (135 ) (61 ) (34 ) Total losses and LAE incurred 2,955 2,762 2,695 Payments for losses and LAE of: Current year (942 ) (841 ) (828 ) Prior years (1,586 ) (1,512 ) (1,575 ) Total payments (2,528 ) (2,353 ) (2,403 ) Reserves of businesses disposed (*) — (40 ) — Foreign currency translation and other 33 (34 ) (11 ) Net liability at end of period 6,721 6,261 5,926 Add back reinsurance recoverables, net of allowance 2,957 2,302 2,201 Gross unpaid losses and LAE included in the balance sheet $ 9,678 $ 8,563 $ 8,127 (*) Reflects the 2016 reinsurance to close transactions at Neon (discussed below). The net decrease in the provision for claims of prior years in 2017 reflects (i) lower than expected losses in the crop and equine businesses and lower than expected claim severity in the property and inland marine and transportation businesses (all within the Property and transportation sub-segment), (ii) favorable reserve development of $18 million on Neon’s exited lines, as well as additional favorable development on ongoing lines of business within Neon, recorded in connection with the reinsurance to close agreement entered into in December 2017 for the 2015 and prior years of account, lower than anticipated claim severity in the workers’ compensation businesses and lower than expected losses in the executive liability business (all within the Specialty casualty sub-segment) and (iii) lower than anticipated claim severity in the fidelity business and lower than expected claim frequency and severity in the surety business (both within the Specialty financial sub-segment). This favorable development was partially offset by (i) the $89 million special charge to increase asbestos and environmental reserves, (ii) higher than expected claim frequency and severity in the ocean marine business (within the Property and transportation sub-segment), (iii) higher than anticipated claim severity in the targeted markets and general liability businesses and higher than anticipated severity in New York contractor claims (all within the Specialty casualty sub-segment) and (iv) a charge to adjust to the deferred gain on the retroactive reinsurance transaction entered into in connection with the sale of businesses in 1998 (included in Other specialty sub-segment). The net increase in the provision for claims of prior years in 2016 reflects (i) the $36 million special charge to increase asbestos and environmental reserves, (ii) reserve strengthening at National Interstate and higher than expected claim frequency in the ocean marine business (within the Property and transportation sub-segment), (iii) adverse reserve development at Neon, higher than anticipated severity in New York contractor claims, higher than anticipated claim frequency and severity in general liability insurance and higher than expected claim frequency and severity in the targeted markets business (within the Specialty casualty sub-segment) and (iv) the $57 million special charge to increase loss reserves related to Neon’s exit of its UK and international medical malpractice and general liability lines of business. This adverse development was partially offset by (i) lower than expected losses in the crop business and lower than expected claim severity in the property and inland marine and trucking businesses (all within the Property and transportation sub-segment), (ii) lower than anticipated claim frequency and severity in workers’ compensation business, lower than expected claim severity in directors and officers liability insurance and lower than expected claim frequency and severity in excess liability business (all within the Specialty casualty sub-segment) and (iii) lower than anticipated claim severity in the fidelity and crime business, lower than expected claim frequency and severity in the surety business and lower than anticipated claim frequency in the financial institutions business (within the Specialty financial sub-segment). The net increase in the provision for claims of prior years in 2015 reflects (i) the $67 million special charge to increase asbestos and environmental reserves, (ii) higher than expected claim severity at National Interstate and higher than anticipated claim frequency in the ocean marine business (all within the Property and transportation sub-segment) and (iii) adverse reserve development at Neon (within the Specialty casualty sub-segment). This adverse development was partially offset by (i) lower than expected claim severity in the property and inland marine business, agricultural operations and a run-off book of homebuilders business (all within the Property and transportation sub-segment), (ii) lower than anticipated claim severity in workers’ compensation business, lower than anticipated claim severity and frequency in excess liability insurance and lower than expected claim severity in directors and officers liability insurance (all within the Specialty casualty sub-segment), and (iii) lower than anticipated claim frequency and severity in the surety business and products for financial institutions and lower than expected claim severity in the fidelity business and run-off collateral value insurance (all within the Specialty financial sub-segment). In December 2017, the Neon Lloyd’s syndicate entered into a reinsurance to close transaction for the 2015 and prior years of account with StarStone Underwriting Limited, a subsidiary of Enstar Group Limited, which will be effective as of December 31, 2017. In the Lloyd’s market, a reinsurance to close transaction transfers the responsibility for discharging all of the liabilities that attach to the transferred year of account plus the right to any income due to the closing year of account in return for a premium. This transaction provides Neon with finality on its legacy business. As a result of the reinsurance to close agreement, Neon was able to better estimate its ultimate liability for the 2015 and prior years of account resulting in favorable development of $42 million , of which $24 million related to its ongoing lines of business (included in Specialty casualty) and $18 million related to its exited lines of business (discussed below and included in Neon exited lines charge). In November 2016, the Neon Lloyd’s syndicate completed a similar reinsurance to close transaction with StarStone, which covered liabilities relating to the syndicate’s 2007 and prior years of account. That transaction also included a quota share of the Italian public hospital business written in Neon’s 2008 year of account and represented Neon’s complete exit from the Italian public hospital medical malpractice business. In May 2015, the FASB issued ASU 2015-09, Financial Services-Insurance: Disclosures about Short-Duration Contracts . The ASU requires insurance entities to disclose incurred and paid claims development information by accident year, net of reinsurance. All of AFG’s material short-duration insurance contracts are written in its property and casualty insurance segment. The development tables and the associated disclosures are aggregated in the following Specialty sub-segments: Property and transportation, Specialty casualty, Specialty financial and Other specialty. See Note C — “ Segments of Operations ” to the financial statements for a discussion of these sub-segments. A reconciliation of incurred and paid claims development information to the aggregate carrying amount of the liability for unpaid losses and LAE, with separate disclosure of reinsurance recoverables on unpaid claims is shown below (in millions): 2017 Unpaid losses and allocated LAE, net of reinsurance: Specialty Property and transportation $ 1,069 Specialty casualty 3,630 Specialty financial 221 Other specialty 278 Total Specialty (excluding foreign reserves) 5,198 Other reserves Reserves for foreign operations: Neon Lloyd’s business 480 Other subsidiaries 269 A&E reserves 403 Unallocated LAE 326 Other 45 Total other reserves 1,523 Total reserves, net of reinsurance 6,721 Add back reinsurance recoverables, net of allowance 2,957 Gross unpaid losses and LAE included in the balance sheet $ 9,678 The following claims development tables and associated disclosures related to short-duration insurance contracts are prepared by sub-segment within the property and casualty insurance business for the most recent 10 accident years. AFG determines its claim counts at the claimant or policy feature level depending on the particular facts and circumstances of the underlying claim. While the methodology is generally consistent within each sub-segment, there are minor differences between and within the sub-segments. The methods used to summarize claim counts have not changed significantly over the time periods reported in the tables below. Property and transportation (Dollars in Millions) Incurred Claims and Allocated LAE, Net of Reinsurance As of December 31, 2017 For the Years Ended (2008–2016 is Supplementary Information and Unaudited) Total IBNR Plus Expected Development on Reported Claims Cumulative Number of Reported Claims Accident Year 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2008 $ 923 $ 871 $ 852 $ 853 $ 856 $ 854 $ 855 $ 856 $ 854 $ 854 $ 1 157,164 2009 526 506 523 516 511 511 508 508 508 3 140,532 2010 702 662 668 676 679 679 683 680 6 140,634 2011 830 816 831 845 856 868 865 10 140,418 2012 890 884 897 909 922 918 19 146,630 2013 911 898 902 908 910 22 142,249 2014 868 852 841 843 38 136,882 2015 842 804 798 54 135,029 2016 771 740 110 122,112 2017 913 273 128,455 Total $ 8,029 Cumulative Paid Claims and Allocated LAE, Net of Reinsurance Accident Year For the Years Ended (2008–2016 is Supplementary Information and Unaudited) 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 % (a) 2008 $ 352 $ 706 $ 761 $ 799 $ 824 $ 835 $ 846 $ 846 $ 847 $ 848 99.3 % 2009 229 348 413 456 479 493 497 499 502 98.8 % 2010 328 505 556 618 649 660 665 669 98.4 % 2011 373 679 742 787 821 840 847 97.9 % 2012 582 725 793 841 868 883 96.2 % 2013 449 721 784 831 862 94.7 % 2014 337 646 711 765 90.7 % 2015 367 595 683 85.6 % 2016 299 534 72.2 % 2017 387 42.4 % Total $ 6,980 Unpaid losses and LAE — years 2008 through 2017 1,049 Unpaid losses and LAE — 11th year and prior (excluding unallocated LAE) 20 Unpaid losses and LAE, net of reinsurance (excluding unallocated LAE) $ 1,069 Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance Year 1 Year 2 Year 3 Year 4 Year 5 Year 6 Year 7 Year 8 Year 9 Year 10 Annual 45.9 % 29.9 % 8.4 % 6.3 % 3.7 % 1.9 % 0.9 % 0.3 % 0.4 % 0.1 % Cumulative 45.9 % 75.8 % 84.2 % 90.5 % 94.2 % 96.1 % 97.0 % 97.3 % 97.7 % 97.8 % (a) Represents the cumulative percentage paid of incurred claims and allocated LAE (net of reinsurance, as estimated at December 31, 2017 ). Specialty casualty (Dollars in Millions) Incurred Claims and Allocated LAE, Net of Reinsurance As of December 31, 2017 For the Years Ended (2008–2016 is Supplementary Information and Unaudited) Total IBNR Plus Expected Development on Reported Claims Cumulative Number of Reported Claims Accident Year 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2008 $ 905 $ 891 $ 874 $ 860 $ 871 $ 856 $ 855 $ 849 $ 855 $ 854 $ 41 59,991 2009 864 867 845 826 816 811 812 807 803 48 53,192 2010 847 863 864 842 856 846 845 842 65 52,855 2011 831 831 819 828 814 808 806 73 50,851 2012 874 865 859 859 855 849 104 49,836 2013 938 921 915 910 913 132 49,412 2014 1,011 984 984 982 202 52,167 2015 1,057 1,023 1,022 268 52,846 2016 1,105 1,098 426 50,652 2017 1,186 715 46,399 Total $ 9,355 Cumulative Paid Claims and Allocated LAE, Net of Reinsurance Accident Year For the Years Ended (2008–2016 is Supplementary Information and Unaudited) 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 % (a) 2008 $ 162 $ 355 $ 490 $ 588 $ 653 $ 702 $ 727 $ 751 $ 768 $ 782 91.6 % 2009 160 366 494 575 636 673 698 713 722 89.9 % 2010 179 393 539 623 676 712 734 748 88.8 % 2011 165 369 506 595 643 674 694 86.1 % 2012 163 368 495 596 658 696 82.0 % 2013 171 377 530 638 698 76.5 % 2014 182 398 556 659 67.1 % 2015 170 398 560 54.8 % 2016 181 404 36.8 % 2017 192 16.2 % Total $ 6,155 Unpaid losses and LAE — years 2008 through 2017 3,200 Unpaid losses and LAE — 11th year and prior (excluding unallocated LAE) 430 Unpaid losses and LAE, net of reinsurance (excluding unallocated LAE) $ 3,630 Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance Year 1 Year 2 Year 3 Year 4 Year 5 Year 6 Year 7 Year 8 Year 9 Year 10 Annual 18.6 % 23.4 % 16.2 % 11.0 % 6.9 % 4.6 % 2.8 % 2.1 % 1.6 % 1.6 % Cumulative 18.6 % 42.0 % 58.2 % 69.2 % 76.1 % 80.7 % 83.5 % 85.6 % 87.2 % 88.8 % (a) Represents the cumulative percentage paid of incurred claims and allocated LAE (net of reinsurance, as estimated at December 31, 2017 ). Specialty financial (Dollars in Millions) Incurred Claims and Allocated LAE, Net of Reinsurance As of December 31, 2017 For the Years Ended (2008–2016 is Supplementary Information and Unaudited) Total IBNR Plus Expected Development on Reported Claims Cumulative Number of Reported Claims Accident Year 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2008 $ 190 $ 207 $ 212 $ 209 $ 203 $ 199 $ 198 $ 197 $ 198 $ 199 $ 1 27,292 2009 193 193 187 184 188 186 187 186 185 — 27,441 2010 139 146 133 133 135 133 130 128 2 21,929 2011 140 158 157 155 148 146 144 11 16,374 2012 164 163 151 139 137 135 11 21,050 2013 141 145 137 131 127 9 28,279 2014 146 157 156 154 16 28,983 2015 156 159 157 21 37,125 2016 179 183 26 43,484 2017 212 84 36,116 Total $ 1,624 Cumulative Paid Claims and Allocated LAE, Net of Reinsurance Accident Year For the Years Ended (2008–2016 is Supplementary Information and Unaudited) 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 % (a) 2008 $ 103 $ 153 $ 185 $ 189 $ 189 $ 191 $ 193 $ 194 $ 194 $ 197 99.0 % 2009 112 145 157 166 171 182 185 186 186 100.5 % 2010 61 93 104 122 133 131 128 127 99.2 % 2011 59 113 116 124 131 132 133 92.4 % 2012 71 104 109 117 121 126 93.3 % 2013 70 100 107 114 117 92.1 % 2014 62 108 125 128 83.1 % 2015 72 109 129 82.2 % 2016 87 141 77.0 % 2017 119 56.1 % Total $ 1,403 Unpaid losses and LAE — years 2008 through 2017 221 Unpaid losses and LAE — 11th year and prior (excluding unallocated LAE) — Unpaid losses and LAE, net of reinsurance (excluding unallocated LAE) $ 221 Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance Year 1 Year 2 Year 3 Year 4 Year 5 Year 6 Year 7 Year 8 Year 9 Year 10 Annual 49.8 % 26.3 % 8.3 % 5.7 % 3.6 % 2.0 % 0.2 % 0.1 % — % 1.5 % Cumulative 49.8 % 76.1 % 84.4 % 90.1 % 93.7 % 95.7 % 95.9 % 96.0 % 96.0 % 97.5 % (a) Represents the cumulative percentage paid of incurred claims and allocated LAE (net of reinsurance, as estimated at December 31, 2017 ). Other specialty (Dollars in Millions) Incurred Claims and Allocated LAE, Net of Reinsurance As of December 31, 2017 For the Years Ended (2008–2016 is Supplementary Information and Unaudited) Total IBNR Plus Expected Development on Reported Claims Cumulative Number of Reported Claims (a) Accident Year 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2008 $ 49 $ 49 $ 49 $ 49 $ 48 $ 46 $ 45 $ 45 $ 44 $ 43 $ 3 — 2009 41 41 41 40 37 37 36 38 33 7 — 2010 36 39 40 39 40 40 40 40 2 — 2011 39 43 42 43 43 44 44 4 — 2012 42 40 39 40 41 39 8 — 2013 46 47 46 47 50 5 — 2014 58 57 59 59 16 — 2015 59 60 63 20 — 2016 61 61 31 — 2017 63 47 — Total $ 495 Cumulative Paid Claims and Allocated LAE, Net of Reinsurance Accident Year For the Years Ended (2008–2016 is Supplementary Information and Unaudited) 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 % (b) 2008 $ 10 $ 16 $ 23 $ 31 $ 35 $ 37 $ 37 $ 37 $ 38 $ 39 90.7 % 2009 8 12 15 19 22 22 24 26 25 75.8 % 2010 8 14 21 24 27 33 35 36 90.0 % 2011 12 20 25 28 34 36 37 84.1 % 2012 8 17 21 25 28 30 76.9 % 2013 7 16 22 34 37 74.0 % 2014 13 21 30 36 61.0 % 2015 10 26 31 49.2 % 2016 9 19 31.1 % 2017 10 15.9 % Total $ 300 Unpaid losses and LAE — years 2008 through 2017 195 Unpaid losses and LAE — 11th year and prior (excluding unallocated LAE) 83 Unpaid losses and LAE, net of reinsurance (excluding unallocated LAE) $ 278 Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance Year 1 Year 2 Year 3 Year 4 Year 5 Year 6 Year 7 Year 8 Year 9 Year 10 Annual 19.8 % 17.3 % 12.5 % 12.8 % 8.9 % 5.9 % 3.3 % 2.9 % (0.4 %) 2.3 % Cumulative 19.8 % 37.1 % 49.6 % 62.4 % 71.3 % 77.2 % 80.5 % 83.4 % 83.0 % 85.3 % (a) The amounts shown in Other specialty represent business assumed by AFG’s internal reinsurance program from the operations that make up AFG’s other Specialty property and casualty insurance sub-segments. Accordingly, the liability for incurred claims and allocated LAE represents additional reserves held on claims counted in the tables provided for the other sub-segments (above). (b) Represents the cumulative percentage paid of incurred claims and allocated LAE (net of reinsurance, as estimated at December 31, 2017 ). Total Specialty Group (Dollars in Millions) Incurred Claims and Allocated LAE, Net of Reinsurance As of December 31, 2017 For the Years Ended (2008–2016 is Supplementary Information and Unaudited) Total IBNR Plus Expected Development on Reported Claims Cumulative Number of Reported Claims Accident Year 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2008 $ 2,067 $ 2,018 $ 1,987 $ 1,971 $ 1,978 $ 1,955 $ 1,953 $ 1,947 $ 1,951 $ 1,950 $ 46 244,447 2009 1,624 1,607 1,596 1,566 1,552 1,545 1,543 1,539 1,529 58 221,165 2010 1,724 1,710 1,705 1,690 1,710 1,698 1,698 1,690 75 215,418 2011 1,840 1,848 1,849 1,871 1,861 1,866 1,859 98 207,643 2012 1,970 1,952 1,946 1,947 1,955 1,941 142 217,516 2013 2,036 2,011 2,000 1,996 2,000 168 219,940 2014 2,083 2,050 2,040 2,038 272 218,032 2015 2,114 2,046 2,040 363 225,000 2016 2,116 2,082 593 216,248 2017 2,374 1,119 210,970 Total $ 19,503 Cumulative Paid Claims and Allocated LAE, Net of Reinsurance Accident Year For the Years Ended (2008–2016 is Supplementary Information and Unaudited) 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 % (a) 2008 $ 627 $ 1,230 $ 1,459 $ 1,607 $ 1,701 $ 1,765 $ 1,803 $ 1,828 $ 1,847 $ 1,866 95.7 % 2009 509 871 1,079 1,216 1,308 1,370 1,404 1,424 1,435 93.9 % 2010 576 1,005 1,220 1,387 1,485 1,536 1,562 1,580 93.5 % 2011 609 1,181 1,389 1,534 1,629 1,682 1,711 92.0 % 2012 824 1,214 1,418 1,579 1,675 1,735 89.4 % 2013 697 1,214 1,443 1,617 1,714 85.7 % 2014 594 1,173 1,422 1,588 77.9 % 2015 619 1,128 1,403 68.8 % 2016 576 1,098 52.7 % 2017 708 29.8 % Total $ 14,838 Unpaid losses and LAE — years 2008 through 2017 4,665 Unpaid losses and LAE — 11th year and prior (excluding unallocated LAE) 533 Unpaid losses and LAE, net of reinsurance (excluding unallocated LAE) $ 5,198 Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance Year 1 Year 2 Year 3 Year 4 Year 5 Year 6 Year 7 Year 8 Year 9 Year 10 Annual 32.7 % 26.1 % 12.1 % 8.5 % 5.3 % 3.3 % 1.8 % 1.2 % 0.8 % 1.0 % Cumulative 32.7 % 58.8 % 70.9 % 79.4 % 84.7 % 88.0 % 89.8 % 91.0 % 91.8 % 92.8 % (a) Represents the cumulative percentage paid of incurred claims and allocated LAE (net of reinsurance, as estimated at December 31, 2017 ). Closed Block of Long-Term Care Insurance Following the completion of the sale of substantially all of its run-off long-term care insurance business in December 2015, AFG’s remaining long-term care insurance reserves were $39 million at December 31, 2017 and $37 million at December 31, 2016 , net of reinsurance recoverables and excluding the impact of unrealized gains on securities. AFG’s remaining outstanding long-term care policies have level premiums and are guaranteed renewable. Premium rates can potentially be increased in reaction to adverse experience; however, any rate increases would require regulatory approval. FHLB Funding Agreements Great American Life Insurance Company (“GALIC”), a wholly-owned annuity subsidiary, is a member of the Federal Home Loan Bank of Cincinnati (“FHLB”). The FHLB makes advances and provides other banking services to member institutions. Members are required to purchase stock in the FHLB in addition to maintaining collateral deposits that back any funds advanced. GALIC’s $44 million investment in FHLB capital stock at December 31, 2017 , is included in other investments at cost. Membership in the FHLB provides the annuity operations with an additional source of liquidity. These advances further the FHLB’s mission of improving access to housing by increasing liquidity in the residential mortgage-backed securities market. In the fourth quarter of 2017 , GALIC refinanced the terms on advances totaling $831 million , which lowered the spread over LIBOR. In the fourth quarter of 2017 , GALIC also repaid $64 million to the FHLB, decreasing the total amount advanced to $871 million (included in annuity benefits accumulated) at December 31, 2017 . Interest rates under the various funding agreements on the advances range from 0.03% to 0.35% over LIBOR (average rate of 1.75% at December 31, 2017 ). While these advances must be repaid between 2018 and 2020 ( $285 million in 2018 and $586 million in 2020), GALIC has the option to prepay all or a portion of the advances. GALIC has invested the proceeds from the advances in fixed maturity securities with similar expected lives as the advances for the purpose of earning a spread over the interest payments due to the FHLB. The advances on these agreements are collateralized by fixed maturity investments, which have a total fair value of $1.04 billion (included in available for sale fixed maturity securities) at December 31, 2017 . Interest credited on the funding agreements, which is included in annuity benefits, was $14 million in 2017 , $8 million in 2016 and $3 million in 2015 . Statutory Information AFG’s U.S.-based insurance subsidiaries are required to file financial statements with state insurance regulatory authorities prepared on an accounting basis prescribed or permitted by such authorities (statutory basis). Net earnings and capital and surplus on a statutory basis for the insurance subsidiaries were as follows (in millions): Net Earnings Capital and Surplus 2017 2016 2015 2017 2016 Property and casualty companies $ 484 $ 461 $ 408 $ 2,729 $ 2,939 Life insurance companies 286 167 399 2,132 1,976 The National Association of Insurance Commissioners’ (“NAIC”) model law for risk based capital (“RBC”) applies to both life and property and casualty insurance companies. RBC formulas determine the amount of capital that an insurance company needs so that it has an acceptable expectation of not becoming financially impaired. Companies below specific trigger points or ratios are subject to regulatory action. At December 31, 2017 and 2016 , the capital ratios of all AFG insurance companies substantially exceeded the RBC requirements. AFG’s insurance companies did not use any prescribed or permitted statutory accounting practices that differed from the NAIC statutory accounting practices at December 31, 2017 or 2016 . Payments of dividends by AFG’s insurance companies are subject to various state laws that limit the amount of dividends that can be paid. Under applicable restrictions, the maximum amount of dividends available to AFG in 2018 from its insurance subsidiaries without seeking regulatory approval is $826 million . Additional amounts of dividends require regulatory approval. AFG paid common stock dividends to shareholders totaling $421 million , $187 million and $178 million in 2017 , 2016 and 2015 , respectively. Currently, there are no regulatory restrictions on AFG’s retained earnings or net earnings that materially impact its ability to pay dividends. Based on shareholders’ equity at December 31, 2017 , AFG could pay dividends in excess of $1 billion without violating its most restrictive debt covenant. However, the payment of future dividends will be at the discretion of AFG’s Board of Directors and will be dependent on many factors including AFG’s financial condition and results of operations, the capital requirements of its insurance subsidiaries, and rating agency commitments. Reinsurance In the normal course of business, AFG’s insurance subsidiaries cede reinsurance to other companies to diversify risk and limit maximum loss arising from large claims. However, AFG remains liable to its insureds regardless of whether a reinsurer is able to meet its obligations. The following table shows (in millions) (i) amounts deducted from property and casualty written and earned premiums in connection with reinsurance ceded, (ii) written and earned premiums included in income for reinsurance assumed and (iii) reinsurance recoveries, which represent ceded losses and loss adjustment expenses. 2017 2016 2015 Direct premiums written $ 6,310 $ 5,858 $ 5,713 Reinsurance assumed 192 123 119 Reinsurance ceded (1,751 ) (1,595 ) (1,505 ) Net written premiums $ 4,751 $ 4,386 $ 4,327 Direct premiums earned $ 6,112 $ 5,745 $ 5,613 Reinsurance assumed 157 118 105 Reinsurance ceded (1,690 ) (1,535 ) (1,494 ) Net earned premiums $ 4,579 $ 4,328 $ 4,224 Reinsurance recoveries $ 1,379 $ 810 $ 936 In June 2017, AFG’s property and casualty insurance subsidiaries entered into a reinsurance agreement to obtain supplemental catastrophe protection through a catastrophe bond structure with Riverfront Re Ltd. (“Riverfront”). The reinsurance agreement provides supplemental reinsurance coverage up to 95% of $200 million (fully collateralized) for catastrophe losses in excess of $100 million (per occurrence and annual aggregate) occurring between June 1, 2017 and December 31, 2020. In connection with the reinsurance agreement, Riverfront issued notes to unrelated investors for the full amount of coverage provided under the reinsurance agreement. Through December 31, 2017 , AFG’s incurred catastrophe losses have not reached the level of attachment for the catastrophe bond structure. Riverfront is a variable interest entity in which AFG does not have a variable interest because the variability in Riverfront’s results will be absorbed entirely by the investors in Riverfront. Accordingly, Riverfront is not consolidated in AFG’s financial statements and the reinsurance ag

Additional Information

Additional Information	12 Months Ended
	Dec. 31, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Additional Information	Additional Information Allowance for Uncollectible Reinsurance AFG’s aggregate allowance for uncollectible reinsurance recoverables was $20 million at December 31, 2017 and $22 million at December 31, 2016 . AFG reviews the allowance quarterly and adjusts it as necessary to reflect changes in estimates of uncollectible balances. AFG recorded net expense reductions against the allowance of less than $1 million in both 2017 and 2016 and $3 million in 2015. In 2017, the allowance was reduced by reinsurance recoverable write-offs of $2 million . Operating Leases Total rental expense for various leases of office space and equipment was $69 million in 2017 , $67 million in 2016 and $70 million in 2015 . Future minimum rentals, related principally to office space, required under operating leases having initial or remaining noncancelable lease terms in excess of one year at December 31, 2017 , were as follows: 2018 – $63 million ; 2019 – $57 million ; 2020 – $50 million ; 2021 – $42 million ; 2022 – $34 million ; and $100 million thereafter. Financial Instruments — Unfunded Commitments On occasion, AFG and its subsidiaries have entered into financial instrument transactions that may present off-balance-sheet risks of both a credit and market risk nature. These transactions include commitments to fund loans, loan guarantees and commitments to purchase and sell securities or loans. At December 31, 2017 , AFG and its subsidiaries had commitments to fund credit facilities and contribute capital to limited partnerships and limited liability corporations of approximately $484 million . Benefit Plans AFG expensed approximately $45 million in 2017 , $43 million in 2016 and $34 million in 2015 for its retirement and employee savings plans.

Condensed Financial Information

Condensed Financial Information of Parent Company	12 Months Ended
	Dec. 31, 2017
Condensed Financial Information of Parent Company Only Disclosure [Abstract]
Condensed Financial Information of Parent Company	AMERICAN FINANCIAL GROUP, INC. — PARENT ONLY SCHEDULE II — CONDENSED FINANCIAL INFORMATION OF REGISTRANT (In Millions) Condensed Balance Sheet December 31, 2017 2016 Assets: Cash and cash equivalents $ 299 $ 197 Investment in securities 70 63 Investment in subsidiaries (a) 6,310 5,989 Other investments 2 2 Other assets 141 136 Total assets $ 6,822 $ 6,387 Liabilities and Equity: Long-term debt $ 1,301 $ 1,283 Other liabilities 191 188 Shareholders’ equity 5,330 4,916 Total liabilities and equity $ 6,822 $ 6,387 Condensed Statement of Earnings Year ended December 31, 2017 2016 2015 Revenues: Dividends from subsidiaries $ 681 $ 643 $ 311 Equity in undistributed earnings of subsidiaries 264 286 386 Investment and other income 13 7 4 Total revenues 958 936 701 Costs and Expenses: Interest charges on intercompany borrowings 9 9 9 Interest charges on other borrowings 85 77 73 Other expenses 142 82 72 Total costs and expenses 236 168 154 Earnings before income taxes 722 768 547 Provision for income taxes 247 119 195 Net Earnings Attributable to Shareholders $ 475 $ 649 $ 352 Condensed Statement of Comprehensive Income Net earnings attributable to shareholders $ 475 $ 649 $ 352 Other comprehensive income (loss), net of tax 296 62 (423 ) Total comprehensive income (loss), net of tax $ 771 $ 711 $ (71 ) ________________________ (a) Investment in subsidiaries includes intercompany receivables and payables. Condensed Statement of Cash Flows Year ended December 31, 2017 2016 2015 Operating Activities: Net earnings attributable to shareholders $ 475 $ 649 $ 352 Adjustments: Equity in net earnings of subsidiaries (575 ) (638 ) (451 ) Dividends from subsidiaries 580 611 280 Other operating activities, net 98 (67 ) (19 ) Net cash provided by operating activities 578 555 162 Investing Activities: Capital contributions to subsidiaries (93 ) (560 ) (27 ) Returns of capital from subsidiaries 30 — 1 Purchases of investments, property and equipment (2 ) (1 ) (10 ) Proceeds from maturities and redemptions of investments 2 1 — Proceeds from sales of investments, property and equipment — — 3 Net cash used in investing activities (63 ) (560 ) (33 ) Financing Activities: Additional long-term borrowings 712 296 145 Reductions of long-term debt (745 ) — (132 ) Issuances of Common Stock 37 35 57 Repurchases of Common Stock — (133 ) (126 ) Cash dividends paid on Common Stock (417 ) (185 ) (176 ) Net cash provided by (used in) financing activities (413 ) 13 (232 ) Net Change in Cash and Cash Equivalents 102 8 (103 ) Cash and cash equivalents at beginning of year 197 189 292 Cash and cash equivalents at end of year $ 299 $ 197 $ 189

Supplementary Insurance Informa

Supplementary Insurance Information	12 Months Ended
	Dec. 31, 2017
Supplementary Insurance Information [Abstract]
Supplementary Insurance Information	AMERICAN FINANCIAL GROUP, INC. AND SUBSIDIARIES SCHEDULE III — SUPPLEMENTARY INSURANCE INFORMATION THREE YEARS ENDED DECEMBER 31, 2017 (IN MILLIONS) Segment Deferred policy acquisition costs Reserves for future policy benefits, claims and unpaid losses and LAE Unearned premiums Net earned premiums Net investment income Benefits, claims, losses and settlement expenses Amortization of deferred policy acquisition costs Other operating expenses Net written premiums (excluding life) 2017 Property and casualty insurance $ 270 $ 9,678 $ 2,410 $ 4,579 $ 362 $ 2,955 $ 556 $ 867 $ 4,751 Annuity 920 33,316 — — 1,458 892 130 159 — Run-off long-term care and life 26 658 — 22 20 26 4 11 3 Other — — — — (9 ) — — 541 — Total $ 1,216 $ 43,652 $ 2,410 $ 4,601 $ 1,831 $ 3,873 $ 690 $ 1,578 $ 4,754 2016 Property and casualty insurance $ 238 $ 8,563 $ 2,171 $ 4,328 $ 350 $ 2,762 $ 520 $ 870 $ 4,386 Annuity 981 29,907 — — 1,356 800 149 142 — Run-off long-term care and life 20 691 — 24 21 33 4 10 3 Other — — — — (31 ) — — 421 — Total $ 1,239 $ 39,161 $ 2,171 $ 4,352 $ 1,696 $ 3,595 $ 673 $ 1,443 $ 4,389 2015 Property and casualty insurance $ 226 $ 8,127 $ 2,060 $ 4,224 $ 319 $ 2,695 $ 511 $ 839 $ 4,327 Annuity 934 26,622 — — 1,224 732 136 123 — Run-off long-term care and life 24 705 — 104 80 131 6 37 73 Other — — — — 10 — — 370 — Total $ 1,184 $ 35,454 $ 2,060 $ 4,328 $ 1,633 $ 3,558 $ 653 $ 1,369 $ 4,400

Accounting Policies (Policies)

Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2017
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The consolidated financial statements include the accounts of American Financial Group, Inc. and its subsidiaries (“AFG”). Certain reclassifications have been made to prior years to conform to the current year’s presentation. All significant intercompany balances and transactions have been eliminated. The results of operations of companies since their formation or acquisition are included in the consolidated financial statements. Events or transactions occurring subsequent to December 31, 2017 , and prior to the filing of this Form 10-K, have been evaluated for potential recognition or disclosure herein. The preparation of the financial statements in conformity with U.S. generally accepted accounting principles (“GAAP”) requires management to make estimates and assumptions that affect the amounts reported in the financial statements and accompanying notes. Changes in circumstances could cause actual results to differ materially from those estimates.
Fair Value Measurements	Fair Value Measurements Accounting standards define fair value as the price that would be received to sell an asset or paid to transfer a liability (an exit price) in an orderly transaction between market participants on the measurement date. The standards establish a hierarchy of valuation techniques based on whether the assumptions that market participants would use in pricing the asset or liability (“inputs”) are observable or unobservable. Observable inputs reflect market data obtained from independent sources, while unobservable inputs reflect AFG’s assumptions about the assumptions market participants would use in pricing the asset or liability. AFG did not have any significant nonrecurring fair value measurements of nonfinancial assets and liabilities in 2017 or 2016 .
Investments	Investments Fixed maturity and equity securities classified as “available for sale” are reported at fair value with unrealized gains and losses included in accumulated other comprehensive income (“AOCI”) in AFG’s Balance Sheet. Fixed maturity and equity securities classified as “trading” are reported at fair value with changes in unrealized holding gains or losses during the period included in net investment income. Mortgage and policy loans are carried primarily at the aggregate unpaid balance. In January 2016, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2016-01, which, among other things, will require all equity securities currently classified as “available for sale” to be reported at fair value, with holding gains and losses recognized in net earnings, instead of AOCI. AFG will be required to adopt this guidance effective January 1, 2018. At the date of adoption, the $221 million net unrealized gain on equity securities included in AOCI as of December 31, 2017 will be reclassified to retained earnings as the cumulative effect of an accounting change. Premiums and discounts on fixed maturity securities are amortized using the effective interest method. Mortgage-backed securities (“MBS”) are amortized over a period based on estimated future principal payments, including prepayments. Prepayment assumptions are reviewed periodically and adjusted to reflect actual prepayments and changes in expectations. Gains or losses on securities are determined on the specific identification basis. When a decline in the value of a specific investment is considered to be other-than-temporary at the balance sheet date, a provision for impairment is charged to earnings (included in realized gains (losses) on securities) and the cost basis of that investment is reduced. If management can assert that it does not intend to sell an impaired fixed maturity security and it is not more likely than not that it will have to sell the security before recovery of its amortized cost basis, then the other-than-temporary impairment is separated into two components: (i) the amount related to credit losses (recorded in earnings) and (ii) the amount related to all other factors (recorded in other comprehensive income). The credit-related portion of an other-than-temporary impairment is measured by comparing a security’s amortized cost to the present value of its current expected cash flows discounted at its effective yield prior to the impairment charge. Both components are shown in the statement of earnings. If management intends to sell an impaired security, or it is more likely than not that it will be required to sell the security before recovery, an impairment charge to earnings is recorded to reduce the amortized cost of that security to fair value.
Derivatives	Derivatives Derivatives included in AFG’s Balance Sheet are recorded at fair value. Changes in fair value of derivatives are included in earnings, unless the derivatives are designated and qualify as highly effective cash flow hedges. Derivatives that do not qualify for hedge accounting under GAAP consist primarily of (i) components of certain fixed maturity securities (primarily interest-only MBS) and (ii) the equity-based component of certain annuity products (included in annuity benefits accumulated) and related equity index call options designed to be consistent with the characteristics of the liabilities and used to mitigate the risk embedded in those annuity products. To qualify for hedge accounting, at the inception of a derivative contract, AFG formally documents the relationship between the terms of the hedge and the hedged items and its risk management objective. This documentation includes defining how hedge effectiveness and ineffectiveness will be measured on a retrospective and prospective basis. Changes in the fair value of derivatives that are designated and qualify as highly effective cash flow hedges are recorded in AOCI and are reclassified into earnings when the variability of the cash flows from the hedged items impacts earnings. Any hedge ineffectiveness is immediately recorded in current period earnings. When the change in the fair value of a qualifying cash flow hedge is included in earnings, it is included in the same line item in the statement of earnings as the cash flows from the hedged item. AFG uses interest rate swaps that are designated and qualify as highly effective cash flow hedges to mitigate interest rate risk related to certain floating-rate securities included in AFG’s portfolio of fixed maturity securities. For derivatives that are designated and qualify as highly effective fair value hedges, changes in the fair value of the derivative, along with changes in the fair value of the hedged item attributable to the hedged risk, are recognized in current period earnings.
Goodwill	Goodwill Goodwill represents the excess of cost of subsidiaries over AFG’s equity in their underlying net assets. Goodwill is not amortized, but is subject to an impairment test at least annually. An entity is not required to complete the quantitative annual goodwill impairment test on a reporting unit if the entity elects to perform a qualitative analysis and determines that it is more likely than not that the reporting unit’s fair value exceeds its carrying amount.
Reinsurance	Reinsurance Amounts recoverable from reinsurers are estimated in a manner consistent with the claim liability associated with the reinsured policies. AFG’s property and casualty insurance subsidiaries report as assets (i) the estimated reinsurance recoverable on paid and unpaid losses, including an estimate for losses incurred but not reported, and (ii) amounts paid or due to reinsurers applicable to the unexpired terms of policies in force. Payable to reinsurers includes ceded premiums due to reinsurers, as well as ceded premiums retained by AFG’s property and casualty insurance subsidiaries under contracts to fund ceded losses as they become due. AFG’s insurance subsidiaries also assume reinsurance from other companies. Earnings on reinsurance assumed is recognized based on information received from ceding companies. An AFG subsidiary cedes life insurance policies to a third party on a funds withheld basis whereby the subsidiary retains the assets (securities) associated with the reinsurance contract. Interest is credited to the reinsurer based on the actual investment performance of the retained assets. This reinsurance contract is considered to contain an embedded derivative (that must be adjusted to fair value) because the yield on the payable is based on a specific block of the ceding company’s assets, rather than the overall creditworthiness of the ceding company. AFG determined that changes in the fair value of the underlying portfolio of fixed maturity securities is an appropriate measure of the value of the embedded derivative. The securities related to this contract are classified as “trading.” The adjustment to fair value on the embedded derivative offsets the investment income recorded on the adjustment to fair value of the related trading portfolio.
Deferred Policy Acquisition Costs (''DPAC'')	Deferred Policy Acquisition Costs (“DPAC”) Policy acquisition costs (principally commissions, premium taxes and certain underwriting and policy issuance costs) directly related to the successful acquisition or renewal of an insurance contract are deferred. DPAC also includes capitalized costs associated with sales inducements offered to fixed annuity policyholders such as enhanced interest rates and premium and persistency bonuses. For the property and casualty companies, DPAC is limited based upon recoverability without any consideration for anticipated investment income and is charged against income ratably over the terms of the related policies. A premium deficiency is recognized if the sum of expected claims costs, claims adjustment expenses and unamortized acquisition costs exceed the related unearned premiums. A premium deficiency is first recognized by charging any unamortized acquisition costs to expense to the extent required to eliminate the deficiency. If the premium deficiency is greater than unamortized acquisition costs, a liability is accrued for the excess deficiency and reported with unpaid losses and loss adjustment expenses. DPAC related to annuities is deferred to the extent deemed recoverable and amortized, with interest, in relation to the present value of actual and expected gross profits on the policies. Expected gross profits consist principally of estimated future investment margin (estimated future net investment income less interest credited on policyholder funds) and surrender, mortality, and other life and annuity policy charges, less death, annuitization and guaranteed withdrawal benefits in excess of account balances and estimated future policy administration expenses. To the extent that realized gains and losses result in adjustments to the amortization of DPAC related to annuities, such adjustments are reflected as components of realized gains (losses) on securities. DPAC related to traditional life and health insurance is amortized over the expected premium paying period of the related policies, in proportion to the ratio of annual premium revenues to total anticipated premium revenues. See “ Life, Accident and Health Reserves ” below for details on the impact of loss recognition on the accounting for traditional life and health insurance contracts. DPAC includes the present value of future profits on business in force of annuity and life, accident and health insurance companies acquired (“PVFP”). PVFP represents the portion of the costs to acquire companies that is allocated to the value of the right to receive future cash flows from insurance contracts existing at the date of acquisition. PVFP is amortized with interest in relation to expected gross profits of the acquired policies for annuities and universal life products and in relation to the premium paying period for traditional life and health insurance products. DPAC and certain other balance sheet amounts related to annuity, long-term care and life businesses are also adjusted, net of tax, for the change in expense that would have been recorded if the unrealized gains (losses) from securities had actually been realized. These adjustments are included in unrealized gains (losses) on marketable securities, a component of AOCI in AFG’s Balance Sheet.
Managed Investment Entities	Managed Investment Entities A company is considered the primary beneficiary of, and therefore must consolidate, a variable interest entity (“VIE”) based primarily on its ability to direct the activities of the VIE that most significantly impact that entity’s economic performance and the obligation to absorb losses of, or receive benefits from, the entity that could potentially be significant to the VIE. AFG manages, and has investments in, collateralized loan obligations (“CLOs”) that are VIEs (see Note H — “ Managed Investment Entities ” ). AFG has determined that it is the primary beneficiary of the CLOs because (i) its role as asset manager gives it the power to direct the activities that most significantly impact the economic performance of the CLOs and (ii) through its investment in the CLO debt tranches, it has exposure to CLO losses (limited to the amount AFG invested) and the right to receive CLO benefits that could potentially be significant to the CLOs. On January 1, 2016, AFG adopted ASU 2015-02, which amended certain consolidation accounting guidance, including the VIE guidance that applies to collateralized financing entities such as CLOs. The new guidance affects how fee arrangements with CLO asset managers impact the determination of the primary beneficiary of those entities. Due to the significance of AFG’s investments in the CLOs that it manages, the new guidance did not impact the consolidation of AFG’s currently outstanding CLOs. The new guidance also impacted the consolidation analysis that applies to limited partnerships and similar entities, but did not result in a change to the accounting for AFG’s existing investments in those entities. Because AFG has no right to use the CLO assets and no obligation to pay the CLO liabilities, the assets and liabilities of the CLOs are shown separately in AFG’s Balance Sheet. AFG has elected the fair value option for reporting on the CLO assets and liabilities to improve the transparency of financial reporting related to the CLOs. The net gain or loss from accounting for the CLO assets and liabilities at fair value is presented separately in AFG’s Statement of Earnings. The fair values of a CLO’s assets may differ from the separately measured fair values of its liabilities even though the CLO liabilities only have recourse to the CLO assets. AFG has set the carrying value of the CLO liabilities equal to the fair value of the CLO assets (which have more observable fair values) as an alternative to reporting those liabilities at a separately measured fair value. CLO earnings attributable to AFG’s shareholders are measured by the change in the fair value of AFG’s investments in the CLOs and management fees earned. Prior to the adoption of new guidance effective January 1, 2015, measuring both the CLO assets and CLO liabilities at separately determined fair values resulted in a difference between the carrying value of the CLO assets and the carrying value of the CLO liabilities that was not attributable to AFG’s ownership interest in the CLOs. This difference was recorded as “appropriated retained earnings — managed investment entities” in AFG’s Balance Sheet. In accordance with the guidance adopted in 2015, the amount reported as “appropriated retained earnings — managed investment entities” at December 31, 2014 was reclassified to “liabilities of managed investment entities” on January 1, 2015 as the cumulative effect of an accounting change.
Unpaid Losses and Loss Adjustment Expenses	Unpaid Losses and Loss Adjustment Expenses The net liabilities stated for unpaid claims and for expenses of investigation and adjustment of unpaid claims represent management’s best estimate and are based upon (i) the accumulation of case estimates for losses reported prior to the close of the accounting period on direct business written; (ii) estimates received from ceding reinsurers and insurance pools and associations; (iii) estimates of unreported losses (including possible development on known claims) based on past experience; (iv) estimates based on experience of expenses for investigating and adjusting claims; and (v) the current state of the law and coverage litigation. Establishing reserves for asbestos, environmental and other mass tort claims involves considerably more judgment than other types of claims due to, among other things, inconsistent court decisions, an increase in bankruptcy filings as a result of asbestos-related liabilities, novel theories of coverage, and judicial interpretations that often expand theories of recovery and broaden the scope of coverage. Loss reserve liabilities are subject to the impact of changes in claim amounts and frequency and other factors. Changes in estimates of the liabilities for losses and loss adjustment expenses are reflected in the statement of earnings in the period in which determined. Despite the variability inherent in such estimates, management believes that the liabilities for unpaid losses and loss adjustment expenses are adequate.
Annuity Benefits Accumulated	Annuity Benefits Accumulated Annuity receipts and benefit payments are recorded as increases or decreases in annuity benefits accumulated rather than as revenue and expense. Increases in this liability for interest credited are charged to expense and decreases for policy charges are credited to other income. For certain products, annuity benefits accumulated also includes reserves for accrued persistency and premium bonuses, guaranteed withdrawals and excess benefits expected to be paid on future deaths and annuitizations (“EDAR”). The liabilities for EDAR and guaranteed withdrawals are accrued for and modified using assumptions consistent with those used in determining DPAC and DPAC amortization, except that amounts are determined in relation to the present value of total expected assessments. Total expected assessments consist principally of estimated future investment margin, surrender, mortality, and other life and annuity policy charges, and unearned revenues once they are recognized as income. Annuity benefits accumulated also includes amounts advanced from the Federal Home Loan Bank of Cincinnati.
Unearned Revenue	Unearned Revenue Certain upfront policy charges on annuities are deferred as unearned revenue (included in other liabilities) and recognized in net earnings (included in other income) using the same assumptions and estimated gross profits used to amortize DPAC.
Life, Accident and Health Reserves	Life, Accident and Health Reserves Liabilities for future policy benefits under traditional life, accident and health policies are computed using the net level premium method. Computations are based on the original projections of investment yields, mortality, morbidity and surrenders and include provisions for unfavorable deviations unless a loss recognition event (premium deficiency) occurs. Claim reserves and liabilities established for accident and health claims are modified as necessary to reflect actual experience and developing trends. For long-duration contracts (such as traditional life and long-term care policies), loss recognition occurs when, based on current expectations as of the measurement date, existing contract liabilities plus the present value of future premiums (including reasonably expected rate increases) are not expected to cover the present value of future claims payments and related settlement and maintenance costs (excluding overhead) as well as unamortized acquisition costs. If a block of business is determined to be in loss recognition, a charge is recorded in earnings in an amount equal to the excess of the present value of expected future claims costs and unamortized acquisition costs over existing reserves plus the present value of expected future premiums (with no provision for adverse deviation). The charge is recorded first to reduce unamortized acquisition costs and then as an additional reserve (if unamortized acquisition costs have been reduced to zero). In addition, reserves for traditional life and long-term care policies are subject to adjustment for loss recognition charges that would have been recorded if the unrealized gains (losses) from securities had actually been realized. This adjustment is included in unrealized gains (losses) on marketable securities, a component of AOCI in AFG’s Balance Sheet.
Debt Issuance Costs	Debt Issuance Costs Debt issuance costs related to AFG’s outstanding debt are amortized over the life of the related debt using the effective interest method. Effective January 1, 2016, AFG adopted (on a retrospective basis) ASU 2015-03, which requires debt issuance costs to be presented in the balance sheet as a direct reduction in the carrying value of long-term debt (consistent with the treatment of debt discounts) with the periodic amortization of such costs included in interest expense. Debt issuance costs related to AFG’s revolving credit facilities will continue to be included in other assets in AFG’s Balance Sheet. Prior to AFG’s adoption of ASU 2015-03, AFG reported unamortized debt issuance costs as a deferred charge asset (included in other assets) in AFG’s Balance Sheet and the periodic amortization was included in other expenses in AFG’s Statement of Earnings. The updated guidance did not affect the overall recognition and measurement guidance for debt issuance costs. Accordingly, the guidance did not have an overall impact on AFG’s Shareholders’ Equity or results of operations.
Variable Annuity Assets and Liabilities	Variable Annuity Assets and Liabilities Separate accounts related to variable annuities represent the fair value of deposits invested in underlying investment funds on which AFG earns a fee. Investment funds are selected and may be changed only by the policyholder, who retains all investment risk. AFG’s variable annuity contracts contain a guaranteed minimum death benefit (“GMDB”) to be paid if the policyholder dies before the annuity payout period commences. In periods of declining equity markets, the GMDB may exceed the value of the policyholder’s account. A GMDB liability is established for future excess death benefits using assumptions together with a range of reasonably possible scenarios for investment fund performance that are consistent with DPAC capitalization and amortization assumptions.
Premium Recognition	Premium Recognition Property and casualty premiums are earned generally over the terms of the policies on a pro rata basis. Unearned premiums represent that portion of premiums written, which is applicable to the unexpired terms of policies in force. On reinsurance assumed from other insurance companies or written through various underwriting organizations, unearned premiums are based on information received from such companies and organizations. For traditional life, accident and health products, premiums are recognized as revenue when legally collectible from policyholders. For interest-sensitive life and universal life products, premiums are recorded in a policyholder account, which is reflected as a liability. Revenue is recognized as amounts are assessed against the policyholder account for mortality coverage and contract expenses.
Noncontrolling Interests	Noncontrolling Interests For balance sheet purposes, noncontrolling interests represent the interests of shareholders other than AFG in consolidated entities. In the statement of earnings, net earnings and losses attributable to noncontrolling interests represents such shareholders’ interest in the earnings and losses of those entities. Noncontrolling interests that are redeemable at the option of the holder are presented separately in the mezzanine section of the balance sheet (between liabilities and equity).
Income Taxes	Income Taxes Deferred income taxes are calculated using the liability method. Under this method, deferred income tax assets and liabilities are determined based on differences between financial reporting and tax bases and are measured using enacted tax rates. A valuation allowance is established to reduce total deferred tax assets to an amount that will more likely than not be realized. AFG recognizes the tax benefits of uncertain tax positions only when the position is more likely than not to be sustained under examination by the appropriate taxing authority. Interest and penalties on AFG’s reserve for uncertain tax positions are recognized as a component of tax expense. The effect of a change in tax rates on deferred tax assets and liabilities is recorded in net earnings in the period that includes the enactment date. This includes the impact on deferred tax assets or liabilities established through AOCI, which results in an amount equal to the difference between the deferred tax at the historical corporate rate and the newly enacted rate stranded in AOCI. As permitted under guidance adopted effective December 31, 2017 (ASU 2018-02), AFG reclassified the $145 million stranded in AOCI from accounting for the Tax Cuts and Jobs Act of 2017 to retained earnings at December 31, 2017. See Note L — “ Income Taxes ” for further information.
Stock-Based Compensation	Stock-Based Compensation All share-based grants are recognized as compensation expense on a straight-line basis over their vesting periods based on their calculated fair value at the date of grant. AFG uses the Black-Scholes pricing model to measure the fair value of employee stock options. See Note K — “ Shareholders’ Equity ” for further information. In the fourth quarter of 2016, AFG early adopted ASU 2016-09, which, among other things, requires excess tax benefits or deficiencies for share-based payments to be recorded through income tax expense in the statement of earnings instead of directly to capital surplus (as required under the previous guidance). As a result, AFG’s Statement of Earnings includes a tax benefit of $17 million in 2017 and $9 million in 2016 that under the previous guidance would have been recorded directly to capital surplus. In addition, the new guidance allows entities to elect to account for forfeitures of awards when they occur rather than accruing expense based on an estimate of expected forfeitures (as required under the previous guidance). AFG has elected to account for forfeitures as they occur. The resulting cumulative effect of accounting change of less than $1 million was recorded directly to retained earnings on January 1, 2016.
Benefit Plans	Benefit Plans AFG provides retirement benefits to qualified employees of participating companies through the AFG 401(k) Retirement and Savings Plan, a defined contribution plan. AFG makes all contributions to the retirement fund portion of the plan and matches a percentage of employee contributions to the savings fund. Company contributions are expensed in the year for which they are declared. AFG and many of its subsidiaries provide health care and life insurance benefits to eligible retirees. AFG also provides postemployment benefits to former or inactive employees (primarily those on disability) who were not deemed retired under other company plans. The projected future cost of providing these benefits is expensed over the period employees earn such benefits.
Earnings Per Share	Earnings Per Share Although basic earnings per share only considers shares of common stock outstanding during the period, the calculation of diluted earnings per share includes the following adjustments to weighted average common shares related to stock-based compensation plans: 2017 – 2.0 million , 2016 – 1.6 million and 2015 – 1.8 million . AFG’s weighted average diluted shares outstanding excludes the following anti-dilutive potential common shares related to stock compensation plans: 2017 – none , 2016 – 0.4 million and 2015 – 1.1 million . Adjustments to net earnings attributable to shareholders in the calculation of diluted earnings per share were nominal in the 2017 , 2016 and 2015 periods.
Statement of Cash Flows	Statement of Cash Flows For cash flow purposes, “investing activities” are defined as making and collecting loans and acquiring and disposing of debt or equity instruments and property and equipment. “Financing activities” include obtaining resources from owners and providing them with a return on their investments, borrowing money and repaying amounts borrowed. Annuity receipts, surrenders, benefits and withdrawals are also reflected as financing activities. All other activities are considered “operating.” Short-term investments having original maturities of three months or less when purchased are considered to be cash equivalents for purposes of the financial statements. Effective October 1, 2016, AFG early adopted (on a retrospective basis) ASU 2016-15, which addresses the diversity in practice in how certain cash receipts and cash payments are presented in the statement of cash flows. Among other things, this guidance requires proceeds received from the settlement of corporate-owned life insurance policies to be classified as cash inflows from investing activities and allows premiums paid for policies to be reported as cash outflows either from investing activities or operating activities. AFG has elected to show all corporate-owned life insurance activity in investing activities. Prior to adoption of this guidance, AFG accounted for these transactions as operating activities. In addition, ASU 2016-15 clarifies when distributions received from investees accounted under the equity method should be accounted for as a cash inflow from operating activities or as a cash inflow from investing activities. AFG had previously accounted for all distributions from investments accounted for under the equity method as investing activities. The new guidance solely related to the presentation of certain transactions in the statement of cash flows. Accordingly, adoption of this guidance did not impact AFG’s results of operations or financial position.
Revenue Recognition Guidance Effective in 2018	Revenue Recognition Guidance Effective in 2018 In May 2014, the FASB issued ASU 2014-09, which requires an entity to recognize revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. Revenue is recognized when (or as) the entity satisfies a performance obligation under the contract. The new guidance also updates the accounting for certain costs associated with obtaining and fulfilling contracts with customers and requires disclosures regarding the nature, amount, timing and uncertainty of revenue and cash flows arising from contracts with customers. Revenue recognition for insurance contracts and financial instruments, which are AFG’s primary sources of revenue, is excluded from the scope of the new guidance. AFG will adopt the new guidance effective January 1, 2018. Because the new guidance would have applied to 2% of AFG’s 2017 consolidated revenues and the impact of the new guidance on the recognition of those revenues would not have been material, management does not expect the new guidance to have a material impact on AFG’s results of operations and financial position.

Acquisitions and Sale of Busi27

Acquisitions and Sale of Businesses (Tables)	12 Months Ended
	Dec. 31, 2017
Business Combinations [Abstract]
Summarized financial information	The impact of the sale of the run-off long-term care insurance business is shown below (in millions): December 24, 2015 Net sale proceeds (*) $ 13 Assets of businesses sold: Cash and investments $ 1,334 Recoverables from reinsurers 630 Deferred policy acquisition costs 16 Other receivables 16 Other assets (4 ) Goodwill 2 Total assets 1,994 Liabilities of businesses sold: Annuity benefits accumulated 261 Life, accident and health reserves 1,525 Other liabilities 7 Total liabilities 1,793 Reclassify net unrealized gain on marketable securities 22 Net assets of businesses sold 179 Loss on subsidiaries, pretax (166 ) Tax benefit 58 Loss on subsidiaries, net of tax $ (108 ) (*) Includes the fair value of the potential additional consideration and capital maintenance agreement and is shown net of estimated expenses. Revenues, costs and expenses, and earnings before income taxes for the subsidiaries sold were (in millions): Year ended December 31, 2015 Life, accident and health net earned premiums: Long-term care $ 73 Life operations 11 Net investment income 73 Realized gains (losses) on securities and other income (11 ) Total revenues 146 Annuity benefits 8 Life, accident and health benefits: Long-term care 91 Life operations 11 Annuity and supplemental insurance acquisition expenses 12 Other expenses 16 Total costs and expenses 138 Earnings before income taxes $ 8

Segments of Operations (Tables)

Segments of Operations (Tables)	12 Months Ended
	Dec. 31, 2017
Segment Reporting [Abstract]
Segment Reporting Information, by Segment	The following tables (in millions) show AFG’s assets, revenues and earnings before income taxes by segment and sub-segment. 2017 2016 2015 Assets Property and casualty insurance (a) $ 17,171 $ 15,574 $ 14,689 Annuity 37,179 33,409 29,865 Run-off long-term care and life 730 752 772 Other 5,578 5,337 4,511 Total assets $ 60,658 $ 55,072 $ 49,837 Revenues Property and casualty insurance: Premiums earned: Specialty Property and transportation $ 1,711 $ 1,662 $ 1,599 Specialty casualty 2,186 2,006 2,011 Specialty financial 576 557 517 Other specialty 106 103 97 Total premiums earned 4,579 4,328 4,224 Net investment income 362 350 319 Other income (b) 28 51 78 Total property and casualty insurance 4,969 4,729 4,621 Annuity: Net investment income 1,458 1,356 1,224 Other income 103 103 98 Total annuity 1,561 1,459 1,322 Run-off long-term care and life (c) 47 49 188 Other 283 240 194 Total revenues before realized gains (losses) 6,860 6,477 6,325 Realized gains (losses) on securities 5 19 (19 ) Realized gains (losses) on subsidiaries — 2 (161 ) Total revenues $ 6,865 $ 6,498 $ 6,145 (a) Not allocable to sub-segments. (b) Includes income of $32 million (before noncontrolling interest) from the sale of an apartment property in 2016 and $66 million (before noncontrolling interest) from the sales of a hotel and an apartment property in 2015. (c) AFG sold substantially all of its run-off long-term care insurance business in December 2015. 2017 2016 2015 Earnings Before Income Taxes Property and casualty insurance: Underwriting: Specialty Property and transportation $ 154 $ 166 $ 48 Specialty casualty 104 78 146 Specialty financial 61 84 87 Other specialty (2 ) 9 14 Other lines (a) (75 ) (101 ) (70 ) Total underwriting 242 236 225 Investment and other income, net (b) 349 341 351 Total property and casualty insurance 591 577 576 Annuity 380 368 331 Run-off long-term care and life (c) 6 2 14 Other (d) (258 ) (181 ) (176 ) Total earnings before realized gains (losses) and income taxes 719 766 745 Realized gains (losses) on securities 5 19 (19 ) Realized gains (losses) on subsidiaries — 2 (161 ) Total earnings before income taxes $ 724 $ 787 $ 565 (a) Includes special charges to increase asbestos and environmental (“A&E”) reserves of $89 million , $36 million and $67 million in 2017 , 2016 and 2015 , respectively. Also includes $18 million in favorable development related to the Neon exited lines recorded in connection with a reinsurance to close transaction in 2017 and a charge of $65 million related to Neon exited lines in 2016. (b) Includes income of $32 million (before noncontrolling interest) from the sale of an apartment property in 2016 and $66 million (before noncontrolling interest) from the sales of a hotel and an apartment property in 2015. (c) AFG sold substantially all of its run-off long-term care insurance business in December 2015. (d) Primarily holding company interest and expenses, including losses on retirement of debt of $51 million in 2017 and $4 million in 2015, and special charges to increase A&E reserves related to AFG’s former railroad and manufacturing operations ( $24 million in 2017 , $5 million in 2016 and $12 million in 2015 ).

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2017
Fair Value Disclosures [Abstract]
Assets and liabilities measured at fair value	Assets and liabilities measured and carried at fair value in the financial statements are summarized below (in millions): Level 1 Level 2 Level 3 Total December 31, 2017 Assets: Available for sale (“AFS”) fixed maturities: U.S. Government and government agencies $ 122 $ 112 $ 8 $ 242 States, municipalities and political subdivisions — 6,975 148 7,123 Foreign government — 127 — 127 Residential MBS — 3,105 122 3,227 Commercial MBS — 926 36 962 Asset-backed securities (“ABS”) — 7,218 744 7,962 Corporate and other 30 17,662 1,044 18,736 Total AFS fixed maturities 152 36,125 2,102 38,379 Trading fixed maturities 44 304 — 348 Equity securities — AFS and trading 1,411 86 165 1,662 Assets of managed investment entities (“MIE”) 307 4,572 23 4,902 Variable annuity assets (separate accounts) (*) — 644 — 644 Equity index call options — 701 — 701 Other assets — derivatives — — — — Total assets accounted for at fair value $ 1,914 $ 42,432 $ 2,290 $ 46,636 Liabilities: Liabilities of managed investment entities $ 293 $ 4,372 $ 22 $ 4,687 Derivatives in annuity benefits accumulated — — 2,542 2,542 Other liabilities — derivatives — 35 — 35 Total liabilities accounted for at fair value $ 293 $ 4,407 $ 2,564 $ 7,264 December 31, 2016 Assets: Available for sale fixed maturities: U.S. Government and government agencies $ 133 $ 174 $ 8 $ 315 States, municipalities and political subdivisions — 6,641 140 6,781 Foreign government — 136 — 136 Residential MBS — 3,445 190 3,635 Commercial MBS — 1,468 25 1,493 Asset-backed securities — 5,475 484 5,959 Corporate and other 29 15,484 712 16,225 Total AFS fixed maturities 162 32,823 1,559 34,544 Trading fixed maturities 30 329 — 359 Equity securities — AFS and trading 1,305 79 174 1,558 Assets of managed investment entities 380 4,356 29 4,765 Variable annuity assets (separate accounts) (*) — 600 — 600 Equity index call options — 492 — 492 Other assets — derivatives — 1 — 1 Total assets accounted for at fair value $ 1,877 $ 38,680 $ 1,762 $ 42,319 Liabilities: Liabilities of managed investment entities $ 363 $ 4,158 $ 28 $ 4,549 Derivatives in annuity benefits accumulated — — 1,759 1,759 Derivatives in long-term debt — (1 ) — (1 ) Other liabilities — derivatives — 30 — 30 Total liabilities accounted for at fair value $ 363 $ 4,187 $ 1,787 $ 6,337 (*) Variable annuity liabilities equal the fair value of variable annuity assets.
Fair value measurements, Levels 1 and 2 transfers	The transfers between Level 1 and Level 2 for the years ended December 31, 2017 , 2016 and 2015 are reflected in the table below at fair value as of the end of the reporting period (dollars in millions): Level 2 To Level 1 Transfers Level 1 To Level 2 Transfers # of Transfers Fair Value # of Transfers Fair Value 2017 2016 2015 2017 2016 2015 2017 2016 2015 2017 2016 2015 Perpetual preferred stocks 4 6 5 $ 23 $ 35 $ 19 2 7 7 $ 11 $ 28 $ 31 Common stocks — 3 7 — — 80 1 2 — — — — Redeemable preferred stocks — — 2 — — 11 — — — — — —
Unobservable inputs used by management in determining fair value of embedded derivatives	The following table presents information about the unobservable inputs used by management in determining fair value of these embedded derivatives. See Note F — “ Derivatives .” Unobservable Input Range Adjustment for insurance subsidiary’s credit risk 0.2% – 2.0% over the risk free rate Risk margin for uncertainty in cash flows 0.70% reduction in the discount rate Surrenders 3% – 23% of indexed account value Partial surrenders 2% – 10% of indexed account value Annuitizations 0.1% – 1% of indexed account value Deaths 1.6% – 8.0% of indexed account value Budgeted option costs 2.4% – 3.6% of indexed account value
Changes in asset balances of Level 3 financial assets	Changes in balances of Level 3 financial assets and liabilities carried at fair value during 2017 , 2016 and 2015 are presented below (in millions). The transfers into and out of Level 3 were due to changes in the availability of market observable inputs. All transfers are reflected in the table at fair value as of the end of the reporting period. Total realized/unrealized gains (losses) included in Balance at December 31, 2016 Net earnings Other comprehensive income (loss) Purchases and issuances Sales and settlements Transfer into Level 3 Transfer out of Level 3 Balance at December 31, 2017 AFS fixed maturities: U.S. government agency $ 8 $ — $ — $ — $ — $ — $ — $ 8 State and municipal 140 — 2 — (2 ) 10 (2 ) 148 Residential MBS 190 (4 ) 2 1 (40 ) 44 (71 ) 122 Commercial MBS 25 2 — 15 (10 ) 4 — 36 Asset-backed securities 484 — 1 410 (132 ) 202 (221 ) 744 Corporate and other 712 (5 ) 2 606 (237 ) 29 (63 ) 1,044 Total AFS fixed maturities 1,559 (7 ) 7 1,032 (421 ) 289 (357 ) 2,102 Equity securities 174 (21 ) 10 38 (16 ) — (20 ) 165 Assets of MIE 29 (11 ) — 9 — — (4 ) 23 Total Level 3 assets $ 1,762 $ (39 ) $ 17 $ 1,079 $ (437 ) $ 289 $ (381 ) $ 2,290 Embedded derivatives (a) $ (1,759 ) $ (589 ) $ — $ (300 ) $ 106 $ — $ — $ (2,542 ) Total Level 3 liabilities (b) $ (1,759 ) $ (589 ) $ — $ (300 ) $ 106 $ — $ — $ (2,542 ) (a) Total realized/unrealized gains (losses) included in net earnings for the embedded derivatives reflects losses related to the unlocking of actuarial assumptions of $25 million in 2017 . (b) As previously discussed, these tables exclude the portion of MIE liabilities allocated to Level 3, which are derived from the fair value of the MIE assets. Total realized/unrealized Balance at December 31, 2015 Net Other Purchases Sales and Transfer Transfer Balance at December 31, 2016 AFS fixed maturities: U.S. government agency $ 15 $ (8 ) $ 1 $ — $ — $ — $ — $ 8 State and municipal 89 — (4 ) 57 (2 ) — — 140 Residential MBS 224 (4 ) (2 ) 8 (28 ) 34 (42 ) 190 Commercial MBS 39 (1 ) — — (7 ) — (6 ) 25 Asset-backed securities 470 (1 ) 1 50 (52 ) 60 (44 ) 484 Corporate and other 633 — (10 ) 176 (100 ) 30 (17 ) 712 Total AFS fixed maturities 1,470 (14 ) (14 ) 291 (189 ) 124 (109 ) 1,559 Equity securities 140 (12 ) 35 44 (28 ) 15 (20 ) 174 Assets of MIE 26 (9 ) — 12 — — — 29 Total Level 3 assets $ 1,636 $ (35 ) $ 21 $ 347 $ (217 ) $ 139 $ (129 ) $ 1,762 Embedded derivatives (a) $ (1,369 ) $ (211 ) $ — $ (277 ) $ 98 $ — $ — $ (1,759 ) Total Level 3 liabilities (b) $ (1,369 ) $ (211 ) $ — $ (277 ) $ 98 $ — $ — $ (1,759 ) (a) Total realized/unrealized gains (losses) included in net earnings for the embedded derivatives reflects losses related to the unlocking of actuarial assumptions of $17 million in 2016 . (b) As previously discussed, these tables exclude the portion of MIE liabilities allocated to Level 3, which are derived from the fair value of the MIE assets. Total realized/unrealized gains (losses) included in Bal. at Dec. 31, 2014 Impact of Net earnings Other comprehensive income (loss) Purchases and issuances Sales and settlements Transfer into Level 3 Transfer out of Level 3 Sale of subsidiaries Bal. at Dec. 31, 2015 AFS fixed maturities: U.S. government agency $ 15 $ — $ — $ — $ — $ — $ — $ — $ — $ 15 State and municipal 100 — — (1 ) 34 (1 ) 2 (39 ) (6 ) 89 Residential MBS 300 — (11 ) (1 ) — (34 ) 86 (88 ) (28 ) 224 Commercial MBS 44 — (1 ) (1 ) — (2 ) 4 (1 ) (4 ) 39 Asset-backed securities 226 — 1 (7 ) 265 (56 ) 53 (10 ) (2 ) 470 Corporate and other 546 — (5 ) (9 ) 161 (90 ) 41 (5 ) (6 ) 633 Total AFS fixed maturities 1,231 — (16 ) (19 ) 460 (183 ) 186 (143 ) (46 ) 1,470 Equity securities 93 — (4 ) (9 ) 77 — — (17 ) — 140 Assets of MIE 31 — (11 ) — 6 — — — — 26 Total Level 3 assets $ 1,355 $ — $ (31 ) $ (28 ) $ 543 $ (183 ) $ 186 $ (160 ) $ (46 ) $ 1,636 Liabilities of MIE $ (2,701 ) $ 2,701 $ — $ — $ — $ — $ — $ — $ — $ — Embedded derivatives (a) (1,160 ) — (17 ) — (257 ) 65 — — — (1,369 ) Total Level 3 liabilities $ (3,861 ) $ 2,701 $ (17 ) $ — $ (257 ) $ 65 $ — $ — $ — $ (1,369 ) (a) Total realized/unrealized gains (losses) included in net earnings for the embedded derivatives reflects losses related to the unlocking of actuarial assumptions of $28 million in 2015 . (b) The impact of implementing new guidance adopted in 2015, as discussed in Note A — “ Accounting Policies — Managed Investment Entities .”
Changes in liability balances of Level 3 financial liabilities	Changes in balances of Level 3 financial assets and liabilities carried at fair value during 2017 , 2016 and 2015 are presented below (in millions). The transfers into and out of Level 3 were due to changes in the availability of market observable inputs. All transfers are reflected in the table at fair value as of the end of the reporting period. Total realized/unrealized gains (losses) included in Balance at December 31, 2016 Net earnings Other comprehensive income (loss) Purchases and issuances Sales and settlements Transfer into Level 3 Transfer out of Level 3 Balance at December 31, 2017 AFS fixed maturities: U.S. government agency $ 8 $ — $ — $ — $ — $ — $ — $ 8 State and municipal 140 — 2 — (2 ) 10 (2 ) 148 Residential MBS 190 (4 ) 2 1 (40 ) 44 (71 ) 122 Commercial MBS 25 2 — 15 (10 ) 4 — 36 Asset-backed securities 484 — 1 410 (132 ) 202 (221 ) 744 Corporate and other 712 (5 ) 2 606 (237 ) 29 (63 ) 1,044 Total AFS fixed maturities 1,559 (7 ) 7 1,032 (421 ) 289 (357 ) 2,102 Equity securities 174 (21 ) 10 38 (16 ) — (20 ) 165 Assets of MIE 29 (11 ) — 9 — — (4 ) 23 Total Level 3 assets $ 1,762 $ (39 ) $ 17 $ 1,079 $ (437 ) $ 289 $ (381 ) $ 2,290 Embedded derivatives (a) $ (1,759 ) $ (589 ) $ — $ (300 ) $ 106 $ — $ — $ (2,542 ) Total Level 3 liabilities (b) $ (1,759 ) $ (589 ) $ — $ (300 ) $ 106 $ — $ — $ (2,542 ) (a) Total realized/unrealized gains (losses) included in net earnings for the embedded derivatives reflects losses related to the unlocking of actuarial assumptions of $25 million in 2017 . (b) As previously discussed, these tables exclude the portion of MIE liabilities allocated to Level 3, which are derived from the fair value of the MIE assets. Total realized/unrealized Balance at December 31, 2015 Net Other Purchases Sales and Transfer Transfer Balance at December 31, 2016 AFS fixed maturities: U.S. government agency $ 15 $ (8 ) $ 1 $ — $ — $ — $ — $ 8 State and municipal 89 — (4 ) 57 (2 ) — — 140 Residential MBS 224 (4 ) (2 ) 8 (28 ) 34 (42 ) 190 Commercial MBS 39 (1 ) — — (7 ) — (6 ) 25 Asset-backed securities 470 (1 ) 1 50 (52 ) 60 (44 ) 484 Corporate and other 633 — (10 ) 176 (100 ) 30 (17 ) 712 Total AFS fixed maturities 1,470 (14 ) (14 ) 291 (189 ) 124 (109 ) 1,559 Equity securities 140 (12 ) 35 44 (28 ) 15 (20 ) 174 Assets of MIE 26 (9 ) — 12 — — — 29 Total Level 3 assets $ 1,636 $ (35 ) $ 21 $ 347 $ (217 ) $ 139 $ (129 ) $ 1,762 Embedded derivatives (a) $ (1,369 ) $ (211 ) $ — $ (277 ) $ 98 $ — $ — $ (1,759 ) Total Level 3 liabilities (b) $ (1,369 ) $ (211 ) $ — $ (277 ) $ 98 $ — $ — $ (1,759 ) (a) Total realized/unrealized gains (losses) included in net earnings for the embedded derivatives reflects losses related to the unlocking of actuarial assumptions of $17 million in 2016 . (b) As previously discussed, these tables exclude the portion of MIE liabilities allocated to Level 3, which are derived from the fair value of the MIE assets. Total realized/unrealized gains (losses) included in Bal. at Dec. 31, 2014 Impact of Net earnings Other comprehensive income (loss) Purchases and issuances Sales and settlements Transfer into Level 3 Transfer out of Level 3 Sale of subsidiaries Bal. at Dec. 31, 2015 AFS fixed maturities: U.S. government agency $ 15 $ — $ — $ — $ — $ — $ — $ — $ — $ 15 State and municipal 100 — — (1 ) 34 (1 ) 2 (39 ) (6 ) 89 Residential MBS 300 — (11 ) (1 ) — (34 ) 86 (88 ) (28 ) 224 Commercial MBS 44 — (1 ) (1 ) — (2 ) 4 (1 ) (4 ) 39 Asset-backed securities 226 — 1 (7 ) 265 (56 ) 53 (10 ) (2 ) 470 Corporate and other 546 — (5 ) (9 ) 161 (90 ) 41 (5 ) (6 ) 633 Total AFS fixed maturities 1,231 — (16 ) (19 ) 460 (183 ) 186 (143 ) (46 ) 1,470 Equity securities 93 — (4 ) (9 ) 77 — — (17 ) — 140 Assets of MIE 31 — (11 ) — 6 — — — — 26 Total Level 3 assets $ 1,355 $ — $ (31 ) $ (28 ) $ 543 $ (183 ) $ 186 $ (160 ) $ (46 ) $ 1,636 Liabilities of MIE $ (2,701 ) $ 2,701 $ — $ — $ — $ — $ — $ — $ — $ — Embedded derivatives (a) (1,160 ) — (17 ) — (257 ) 65 — — — (1,369 ) Total Level 3 liabilities $ (3,861 ) $ 2,701 $ (17 ) $ — $ (257 ) $ 65 $ — $ — $ — $ (1,369 ) (a) Total realized/unrealized gains (losses) included in net earnings for the embedded derivatives reflects losses related to the unlocking of actuarial assumptions of $28 million in 2015 . (b) The impact of implementing new guidance adopted in 2015, as discussed in Note A — “ Accounting Policies — Managed Investment Entities .”
Fair value of financial instruments	The carrying value and fair value of financial instruments that are not carried at fair value in the financial statements at December 31 are summarized below (in millions): Carrying Fair Value Value Total Level 1 Level 2 Level 3 2017 Financial assets: Cash and cash equivalents $ 2,338 $ 2,338 $ 2,338 $ — $ — Mortgage loans 1,125 1,119 — — 1,119 Policy loans 184 184 — — 184 Total financial assets not accounted for at fair value $ 3,647 $ 3,641 $ 2,338 $ — $ 1,303 Financial liabilities: Annuity benefits accumulated (*) $ 33,110 $ 32,461 $ — $ — $ 32,461 Long-term debt 1,301 1,354 — 1,351 3 Total financial liabilities not accounted for at fair value $ 34,411 $ 33,815 $ — $ 1,351 $ 32,464 2016 Financial assets: Cash and cash equivalents $ 2,107 $ 2,107 $ 2,107 $ — $ — Mortgage loans 1,147 1,146 — — 1,146 Policy loans 192 192 — — 192 Total financial assets not accounted for at fair value $ 3,446 $ 3,445 $ 2,107 $ — $ 1,338 Financial liabilities: Annuity benefits accumulated (*) $ 29,703 $ 28,932 $ — $ — $ 28,932 Long-term debt 1,284 1,356 — 1,353 3 Total financial liabilities not accounted for at fair value $ 30,987 $ 30,288 $ — $ 1,353 $ 28,935 (*) Excludes $206 million and $204 million of life contingent annuities in the payout phase at December 31, 2017 and 2016 , respectively.

Investments (Tables)

Investments (Tables)	12 Months Ended
	Dec. 31, 2017
Investments, Debt and Equity Securities [Abstract]
Available for sale fixed maturities and equity securities	Available for sale fixed maturities and equity securities at December 31 consisted of the following (in millions): 2017 2016 Amortized Cost Gross Unrealized Net Unrealized Fair Value Amortized Cost Gross Unrealized Net Unrealized Fair Value Gains Losses Gains Losses Fixed maturities: U.S. Government and government agencies $ 244 $ 1 $ (3 ) $ (2 ) $ 242 $ 315 $ 3 $ (3 ) $ — $ 315 States, municipalities and political subdivisions 6,887 254 (18 ) 236 7,123 6,650 200 (69 ) 131 6,781 Foreign government 124 3 — 3 127 131 5 — 5 136 Residential MBS 2,884 349 (6 ) 343 3,227 3,367 281 (13 ) 268 3,635 Commercial MBS 927 36 (1 ) 35 962 1,446 49 (2 ) 47 1,493 Asset-backed securities 7,836 142 (16 ) 126 7,962 5,962 43 (46 ) (3 ) 5,959 Corporate and other 18,136 638 (38 ) 600 18,736 15,864 473 (112 ) 361 16,225 Total fixed maturities $ 37,038 $ 1,423 $ (82 ) $ 1,341 $ 38,379 $ 33,735 $ 1,054 $ (245 ) $ 809 $ 34,544 Equity Securities: Common stocks $ 786 $ 263 $ (22 ) $ 241 $ 1,027 $ 879 $ 160 $ (23 ) $ 137 $ 1,016 Perpetual preferred stocks 535 39 (1 ) 38 573 472 21 (7 ) 14 486 Total equity securities $ 1,321 $ 302 $ (23 ) $ 279 $ 1,600 $ 1,351 $ 181 $ (30 ) $ 151 $ 1,502
Available for sale securities in a continuous unrealized loss position	The following tables show gross unrealized losses (dollars in millions) on available for sale fixed maturities and equity securities by investment category and length of time that individual securities have been in a continuous unrealized loss position at December 31, 2017 and 2016 . Less Than Twelve Months Twelve Months or More Unrealized Loss Fair Value Fair Value as % of Cost Unrealized Loss Fair Value Fair Value as % of Cost 2017 Fixed maturities: U.S. Government and government agencies $ — $ 55 100 % $ (3 ) $ 123 98 % States, municipalities and political subdivisions (8 ) 825 99 % (10 ) 431 98 % Foreign government — 4 100 % — — — % Residential MBS (1 ) 118 99 % (5 ) 118 96 % Commercial MBS (1 ) 67 99 % — — — % Asset-backed securities (7 ) 1,195 99 % (9 ) 299 97 % Corporate and other (20 ) 2,031 99 % (18 ) 603 97 % Total fixed maturities $ (37 ) $ 4,295 99 % $ (45 ) $ 1,574 97 % Equity securities: Common stocks $ (22 ) $ 117 84 % $ — $ — — % Perpetual preferred stocks — 41 100 % (1 ) 13 93 % Total equity securities $ (22 ) $ 158 88 % $ (1 ) $ 13 93 % 2016 Fixed maturities: U.S. Government and government agencies $ (1 ) $ 153 99 % $ (2 ) $ 8 80 % States, municipalities and political subdivisions (64 ) 2,289 97 % (5 ) 44 90 % Residential MBS (7 ) 502 99 % (6 ) 162 96 % Commercial MBS (2 ) 121 98 % — — — % Asset-backed securities (29 ) 1,737 98 % (17 ) 634 97 % Corporate and other (93 ) 3,849 98 % (19 ) 312 94 % Total fixed maturities $ (196 ) $ 8,651 98 % $ (49 ) $ 1,160 96 % Equity securities: Common stocks $ (23 ) $ 215 90 % $ — $ — — % Perpetual preferred stocks (6 ) 135 96 % (1 ) 6 86 % Total equity securities $ (29 ) $ 350 92 % $ (1 ) $ 6 86 %
Roll forward of cumulative credit portion of other-than-temporary impairments on fixed maturity securities	A progression of the credit portion of other-than-temporary impairments on fixed maturity securities for which the non-credit portion of an impairment has been recognized in other comprehensive income is shown below (in millions): 2017 2016 2015 Balance at January 1 $ 153 $ 160 $ 170 Additional credit impairments on: Previously impaired securities 1 2 1 Securities without prior impairments 3 1 2 Reductions due to: Sales or redemptions (12 ) (10 ) (9 ) Sale of subsidiaries — — (4 ) Balance at December 31 $ 145 $ 153 $ 160
Available for sale fixed maturity securities by contractual maturity date	The table below sets forth the scheduled maturities of available for sale fixed maturities as of December 31, 2017 (dollars in millions). Securities with sinking funds are reported at average maturity. Actual maturities may differ from contractual maturities because certain securities may be called or prepaid by the issuers. Amortized Fair Value Cost Amount % Maturity One year or less $ 746 $ 759 2 % After one year through five years 6,730 6,939 18 % After five years through ten years 13,235 13,662 35 % After ten years 4,680 4,868 13 % 25,391 26,228 68 % ABS (average life of approximately 5 years) 7,836 7,962 21 % MBS (average life of approximately 4.5 years) 3,811 4,189 11 % Total $ 37,038 $ 38,379 100 %
Components of the net unrealized gain on securities, included in Accumulated Other Comprehensive Income	The following table shows (in millions) the components of the net unrealized gain on securities that is included in AOCI in AFG’s Balance Sheet. Pretax Deferred Tax Net December 31, 2017 Net unrealized gain on: Fixed maturities — annuity segment (a) $ 1,082 $ (227 ) $ 855 Fixed maturities — all other 259 (55 ) 204 Total fixed maturities 1,341 (282 ) 1,059 Equity securities (b) 279 (58 ) 221 Total investments 1,620 (340 ) 1,280 Deferred policy acquisition costs — annuity segment (433 ) 91 (342 ) Annuity benefits accumulated (137 ) 29 (108 ) Unearned revenue 13 (3 ) 10 Total net unrealized gain on marketable securities $ 1,063 $ (223 ) $ 840 December 31, 2016 Net unrealized gain on: Fixed maturities — annuity segment (a) $ 640 $ (224 ) $ 416 Fixed maturities — all other 169 (59 ) 110 Total fixed maturities 809 (283 ) 526 Equity securities (b) 151 (53 ) 98 Total investments 960 (336 ) 624 Deferred policy acquisition costs — annuity segment (273 ) 96 (177 ) Annuity benefits accumulated (78 ) 27 (51 ) Unearned revenue 13 (5 ) 8 Total net unrealized gain on marketable securities $ 622 $ (218 ) $ 404 (a) Net unrealized gains on fixed maturity investments supporting AFG’s annuity benefits accumulated. (b) As discussed in Note A — “ Accounting Policies — Investments ,” effective January 1, 2018, all equity securities currently classified as “available for sale” will be required to be carried at fair value through net earnings instead of AOCI.
Real estate and other investments included on the Balance Sheet	Real estate and other investments on AFG’s Balance Sheet includes the following at December 31 (in millions): 2017 2016 Limited partnerships and similar investments accounted for using the equity method $ 999 $ 688 Directly owned real estate 164 197 Other investments 148 149 Total real estate and other investments $ 1,311 $ 1,034
Net investment income earned and investment expenses incurred	The following table shows (in millions) investment income earned and investment expenses incurred. 2017 2016 2015 Investment income: Fixed maturities $ 1,607 $ 1,510 $ 1,461 Equity securities 79 81 76 Equity in earnings of partnerships and similar investments 64 44 27 Other 102 81 87 Gross investment income 1,852 1,716 1,651 Investment expenses (21 ) (20 ) (18 ) Net investment income $ 1,831 $ 1,696 $ 1,633
Realized gains (losses) and changes in unrealized appreciation (depreciation) related to fixed maturity and equity security investments	Realized gains (losses) and changes in unrealized appreciation (depreciation) related to fixed maturity and equity security investments are summarized as follows (in millions): 2017 2016 Realized gains (losses) Realized gains (losses) Before Impairments Impairments Total Change in Unrealized Before Impairments Impairments Total Change in Unrealized Fixed maturities $ 17 $ (20 ) $ (3 ) $ 532 $ 36 $ (38 ) $ (2 ) $ 90 Equity securities 70 (64 ) 6 128 106 (93 ) 13 67 Mortgage loans and other investments (6 ) (4 ) (10 ) — — — — — Other (*) (3 ) 15 12 (219 ) (7 ) 15 8 (52 ) Total pretax 78 (73 ) 5 441 135 (116 ) 19 105 Tax effects (27 ) 25 (2 ) (5 ) (48 ) 41 (7 ) (37 ) Noncontrolling interests — — — — (2 ) 3 1 4 Net of tax and noncontrolling interests $ 51 $ (48 ) $ 3 $ 436 $ 85 $ (72 ) $ 13 $ 72 2015 Realized gains (losses) Before Impairments Impairments Total Change in Unrealized Fixed maturities $ 19 $ (43 ) $ (24 ) $ (941 ) Equity securities 94 (94 ) — (134 ) Mortgage loans and other investments (2 ) (3 ) (5 ) — Other (*) (5 ) 15 10 430 Total pretax 106 (125 ) (19 ) (645 ) Tax effects (38 ) 45 7 226 Noncontrolling interests (2 ) 2 — 8 Net of tax and noncontrolling interests $ 66 $ (78 ) $ (12 ) $ (411 ) (*) Primarily adjustments to deferred policy acquisition costs and reserves related to the annuity business.
Gross realized gains and losses on available for sale fixed maturity and equity security investments	Gross realized gains and losses (excluding impairment write-downs and mark-to-market of derivatives) on available for sale fixed maturity and equity security investment transactions consisted of the following (in millions): 2017 2016 2015 Fixed maturities: Gross gains $ 43 $ 55 $ 38 Gross losses (20 ) (10 ) (7 ) Equity securities: Gross gains 87 110 99 Gross losses (17 ) (4 ) (5 )

Derivatives (Tables)

Derivatives (Tables)	12 Months Ended
	Dec. 31, 2017
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivatives included in Balance Sheet at fair value	The following derivatives that do not qualify for hedge accounting under GAAP are included in AFG’s Balance Sheet at fair value (in millions): December 31, 2017 December 31, 2016 Derivative Balance Sheet Line Asset Liability Asset Liability MBS with embedded derivatives Fixed maturities $ 105 $ — $ 107 $ — Public company warrants Equity securities 4 — 4 — Fixed-indexed annuities (embedded derivative) Annuity benefits accumulated — 2,542 — 1,759 Equity index call options Equity index call options 701 — 492 — Reinsurance contract (embedded derivative) Other liabilities — 4 — 8 $ 810 $ 2,546 $ 603 $ 1,767
Summary of gain (loss) included in the Statement of Earnings for changes in the fair value of derivatives	The following table summarizes the gain (loss) included in AFG’s Statement of Earnings for changes in the fair value of derivatives that do not qualify for hedge accounting for 2017 , 2016 and 2015 (in millions): Derivative Statement of Earnings Line 2017 2016 2015 MBS with embedded derivatives Realized gains (losses) on securities $ (6 ) $ (9 ) $ (16 ) Public company warrants Realized gains (losses) on securities — — — Fixed-indexed annuities (embedded derivative) (*) Annuity benefits (589 ) (211 ) (17 ) Equity index call options Annuity benefits 494 141 (56 ) Reinsurance contracts (embedded derivative) Net investment income (2 ) (1 ) 6 $ (103 ) $ (80 ) $ (83 ) (*) The change in fair value of the embedded derivative includes losses related to unlocking of actuarial assumptions of $25 million in 2017 compared to $17 million in 2016 and $28 million in 2015 .

Deferred Policy Acquisition C32

Deferred Policy Acquisition Costs (Tables)	12 Months Ended
	Dec. 31, 2017
Deferred Policy Acquisition Costs Disclosures [Abstract]
Deferred Policy Acquisition Costs Details	A progression of deferred policy acquisition costs is presented below (in millions): P&C Annuity and Run-off Long-term Care and Life Deferred Deferred Sales Consolidated Costs Costs Inducements PVFP Subtotal Unrealized (*) Total Total Balance at December 31, 2014 $ 221 $ 925 $ 132 $ 74 $ 1,131 $ (531 ) $ 600 $ 821 Additions 519 224 11 — 235 — 235 754 Amortization: Periodic amortization (511 ) (162 ) (26 ) (11 ) (199 ) — (199 ) (710 ) Annuity unlocking — 31 4 — 35 — 35 35 Included in realized gains — 8 1 — 9 — 9 9 Sale of subsidiaries — (8 ) (3 ) (8 ) (19 ) — (19 ) (19 ) Foreign currency translation (3 ) — — — — — — (3 ) Change in unrealized — — — — — 297 297 297 Balance at December 31, 2015 226 1,018 119 55 1,192 (234 ) 958 1,184 Additions 535 230 9 — 239 — 239 774 Amortization: Periodic amortization (520 ) (169 ) (24 ) (9 ) (202 ) — (202 ) (722 ) Annuity unlocking — 25 4 — 29 — 29 29 Included in realized gains — 6 2 — 8 — 8 8 Foreign currency translation (3 ) — — — — — — (3 ) Change in unrealized — — — — — (31 ) (31 ) (31 ) Balance at December 31, 2016 238 1,110 110 46 1,266 (265 ) 1,001 1,239 Additions 588 225 4 — 229 — 229 817 Amortization: Periodic amortization (556 ) (161 ) (19 ) (8 ) (188 ) — (188 ) (744 ) Annuity unlocking — 34 6 1 41 — 41 41 Included in realized gains — 9 1 — 10 — 10 10 Foreign currency translation — — — — — — — — Other — — — 10 10 — 10 10 Change in unrealized — — — — — (157 ) (157 ) (157 ) Balance at December 31, 2017 $ 270 $ 1,217 $ 102 $ 49 $ 1,368 $ (422 ) $ 946 $ 1,216 (*) Unrealized adjustments to DPAC includes net unrealized gains/losses on securities and net unrealized gains/losses on cash flow hedges.

Managed Investment Entities (Ta

Managed Investment Entities (Tables)	12 Months Ended
	Dec. 31, 2017
Variable Interest Entity, Primary Beneficiary, Does Not Hold Majority Voting Interest, Disclosures [Abstract]
Selected financial information related to collateralized loan obligations	Selected financial information related to the CLOs is shown below (in millions): Year ended December 31, 2017 2016 2015 Investment in CLO tranches $ 215 $ 216 $ 266 Gains (losses) on change in fair value of assets/liabilities (a): Assets (8 ) 131 (116 ) Liabilities 20 (116 ) 82 Management fees paid to AFG 18 17 15 CLO earnings (losses) attributable to AFG Shareholders (b) 23 37 (6 ) (a) Included in revenues in AFG’s Statement of Earnings. (b) Included in earnings before income taxes in AFG’s Statement of Earnings.

Goodwill and Other Intangibles

Goodwill and Other Intangibles (Tables)	12 Months Ended
	Dec. 31, 2017
Goodwill and Intangible Assets Disclosure [Abstract]
Changes in the carrying value of goodwill by reporting segment	Changes in the carrying value of goodwill during 2015 , 2016 and 2017 , by reporting segment, are presented in the following table (in millions): Property and Casualty Annuity Total Balance at January 1, 2015 $ 168 $ 33 $ 201 Sale of subsidiaries in 2015 — (2 ) (2 ) Balance at December 31, 2015, December 31, 2016 and December 31, 2017 $ 168 $ 31 $ 199

Long-Term Debt (Tables)

Long-Term Debt (Tables)	12 Months Ended
	Dec. 31, 2017
Debt Disclosure [Abstract]
Schedule of long-term debt instruments	Long-term debt consisted of the following at December 31 (in millions): 2017 2016 Principal Discount and Issue Costs Carrying Value Principal Discount and Issue Costs Carrying Value Direct Senior Obligations of AFG: 4.50% Senior Notes due June 2047 $ 590 $ (2 ) $ 588 $ — $ — $ — 3.50% Senior Notes due August 2026 425 (5 ) 420 300 (3 ) 297 9-7/8% Senior Notes due June 2019 — — — 350 (1 ) 349 6-3/8% Senior Notes due June 2042 — — — 230 (7 ) 223 5-3/4% Senior Notes due August 2042 — — — 125 (4 ) 121 Other 3 — 3 3 — 3 1,018 (7 ) 1,011 1,008 (15 ) 993 Direct Subordinated Obligations of AFG: 6-1/4% Subordinated Debentures due September 2054 150 (5 ) 145 150 (5 ) 145 6% Subordinated Debentures due November 2055 150 (5 ) 145 150 (5 ) 145 300 (10 ) 290 300 (10 ) 290 $ 1,318 $ (17 ) $ 1,301 $ 1,308 $ (25 ) $ 1,283

Shareholders' Equity (Tables)

Shareholders' Equity (Tables)	12 Months Ended
	Dec. 31, 2017
Stockholders' Equity Note [Abstract]
Summary of restricted stock awards activity	The restricted Common Stock that AFG has granted generally vests over a three or four year period. Data relating to grants of restricted stock is presented below: Shares Average Grant Date Fair Value Outstanding at January 1, 2017 678,875 $ 60.90 Granted 232,250 $ 94.44 Vested (145,473 ) $ 48.76 Forfeited (6,617 ) $ 71.30 Outstanding at December 31, 2017 759,035 $ 73.40
Summary of stock options activity	Data for stock options issued under AFG’s stock incentive plans is presented below: Shares Average Exercise Price Average Remaining Contractual Term Aggregate Intrinsic Value (in millions) Outstanding at January 1, 2017 4,505,101 $ 43.02 Exercised (1,020,986 ) $ 33.38 Forfeited/Cancelled (16,775 ) $ 55.82 Outstanding at December 31, 2017 3,467,340 $ 45.80 4.9 years $ 218 Options exercisable at December 31, 2017 2,589,277 $ 42.00 4.4 years $ 172
Assumptions used in estimating weighted average fair value of options on grant date	The risk-free rate for periods associated with the expected term is based upon the U.S. Treasury yield curve in effect on the grant date. 2015 Exercise price $ 63.15 Expected dividend yield 1.6 % Expected volatility 25 % Expected term (in years) 7.25 Risk-free rate 1.88 % Grant date fair value $ 15.29
Components of accumulated other comprehensive income (loss)	The progression of the components of accumulated other comprehensive income follows (in millions): Other Comprehensive Income AOCI Beginning Balance Pretax Tax Net of tax Attributable to noncontrolling interests Attributable to shareholders Other (c) AOCI Ending Balance Year ended December 31, 2017 Net unrealized gains on securities: Unrealized holding gains on securities arising during the period $ 456 $ (159 ) $ 297 $ — $ 297 Reclassification adjustment for realized (gains) losses included in net earnings (a) (15 ) 5 (10 ) — (10 ) Total net unrealized gains on securities (b) $ 404 441 (154 ) 287 — 287 $ 149 $ 840 Net unrealized losses on cash flow hedges (7 ) (6 ) 2 (4 ) — (4 ) (2 ) (13 ) Foreign currency translation adjustments (15 ) 9 3 12 — 12 (3 ) (6 ) Pension and other postretirement plans adjustments (7 ) 1 — 1 — 1 (2 ) (8 ) Total $ 375 $ 445 $ (149 ) $ 296 $ — $ 296 $ 142 $ 813 Year ended December 31, 2016 Net unrealized gains on securities: Unrealized holding gains on securities arising during the period $ 124 $ (44 ) $ 80 $ (4 ) $ 76 Reclassification adjustment for realized (gains) losses included in net earnings (a) (19 ) 7 (12 ) (1 ) (13 ) Total net unrealized gains on securities (b) $ 332 105 (37 ) 68 (5 ) 63 $ 9 $ 404 Net unrealized gains (losses) on cash flow hedges 1 (12 ) 4 (8 ) — (8 ) — (7 ) Foreign currency translation adjustments (22 ) 6 1 7 — 7 — (15 ) Pension and other postretirement plans adjustments (7 ) — — — — — — (7 ) Total $ 304 $ 99 $ (32 ) $ 67 $ (5 ) $ 62 $ 9 $ 375 Year ended December 31, 2015 Net unrealized gains (losses) on securities: Unrealized holding losses on securities arising during the period $ (625 ) $ 219 $ (406 ) $ 9 $ (397 ) Reclassification adjustment for realized (gains) losses included in net earnings (a) 14 (5 ) 9 (1 ) 8 Reclassification for unrealized gains of subsidiaries sold (34 ) 12 (22 ) — (22 ) Total net unrealized gains (losses) on securities (b) $ 743 (645 ) 226 (419 ) 8 (411 ) $ — $ 332 Net unrealized gains on cash flow hedges — 1 — 1 — 1 — 1 Foreign currency translation adjustments (8 ) (9 ) (5 ) (14 ) — (14 ) — (22 ) Pension and other postretirement plans adjustments (8 ) 1 — 1 — 1 — (7 ) Total $ 727 $ (652 ) $ 221 $ (431 ) $ 8 $ (423 ) $ — $ 304 (a) The reclassification adjustment out of net unrealized gains on securities affected the following lines in AFG’s Statement of Earnings: OCI component Affected line in the statement of earnings Pretax Realized gains (losses) on securities Tax Provision for income taxes Attributable to noncontrolling interests Net earnings attributable to noncontrolling interests (b) Includes net unrealized gains of $68 million at December 31, 2017 compared to net unrealized gains of $52 million and $51 million at December 31, 2016 and 2015 , related to securities for which only the credit portion of an other-than-temporary impairment has been recorded in earnings. (c) Other includes the December 2017 reclassification of $145 million stranded in AOCI from accounting for the Tax Cuts and Jobs Act of 2017 to retained earnings (see Note A — “ Accounting Policies — Income Taxes ”) , and the impact on AOCI of the December 2017 sale of redeemable noncontrolling interests in Neon and the November 2016 acquisition of the noncontrolling interest in NATL (see Note B — “ Acquisitions and Sale of Businesses ”).

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Reconciliation of income taxes at the statutory rate and income taxes shown in the Statement of Earnings	The following is a reconciliation of income taxes at the statutory rate of 35% to the provision for income taxes as shown in AFG’s Statement of Earnings (dollars in millions): 2017 2016 2015 Amount % of EBT Amount % of EBT Amount % of EBT Earnings before income taxes (“EBT”) $ 724 $ 787 $ 565 Income taxes at statutory rate $ 253 35 % $ 275 35 % $ 198 35 % Effect of: Tax exempt interest (23 ) (3 %) (24 ) (3 %) (27 ) (5 %) Dividend received deduction (8 ) (1 %) (7 ) (1 %) (8 ) (1 %) Stock-based compensation (16 ) (2 %) (9 ) (1 %) 1 — % Employee stock ownership plan dividend paid deduction (5 ) (1 %) (2 ) — % (1 ) — % Foreign operations 21 3 % 5 — % 3 1 % Change in valuation allowance (excluding change in tax rate) (7 ) (1 %) 52 7 % 23 4 % Subsidiaries not in AFG’s tax return — — % 3 — % 2 — % Neon restructuring (56 ) (8 %) (111 ) (14 %) — — % Change in U.S corporate tax rate 83 11 % — — % — — % Acquisition of noncontrolling interest in NATL — — % (66 ) (8 %) — — % Other 5 1 % 3 — % 4 1 % Provision for income taxes as shown in the statement of earnings $ 247 34 % $ 119 15 % $ 195 35 %
Components of income tax provision (credit)	The total income tax provision (credit) consists of (in millions): 2017 2016 2015 Current taxes: Federal $ 153 $ 299 $ 216 State 6 12 8 Deferred taxes: Federal 5 (192 ) (29 ) Impact of change in U.S. corporate tax rate 83 — — Total Federal deferred taxes 88 (192 ) (29 ) Provision for income taxes $ 247 $ 119 $ 195
Summary of operating loss carryforwards	For income tax purposes, AFG and its subsidiaries had the following carryforwards available at December 31, 2017 (in millions): Expiring Amount Operating Loss – U.S. 2018 - 2022 $ 130 Operating Loss – United Kingdom indefinite 252 (*) Capital Loss – U.S. 2022 109 (*) £186 million
Components of deferred tax assets and liabilities	Deferred income tax assets and liabilities reflect temporary differences between the carrying amounts of assets and liabilities recognized for financial reporting purposes and the amounts recognized for tax purposes. The significant components of deferred tax assets and liabilities included in AFG’s Balance Sheet at December 31 were as follows (in millions): 2017 2016 Excluding Unrealized Gains Impact of Unrealized Gains Total Excluding Unrealized Gains Impact of Unrealized Gains Total Deferred tax assets: Federal net operating loss carryforwards $ 27 $ — $ 27 $ 50 $ — $ 50 Foreign underwriting losses 80 — 80 120 — 120 Capital loss carryforwards 32 — 32 83 — 83 Insurance claims and reserves 665 29 694 774 27 801 Employee benefits 84 — 84 131 — 131 Other, net 48 (3 ) 45 85 (5 ) 80 Total deferred tax assets before valuation allowance 936 26 962 1,243 22 1,265 Valuation allowance against deferred tax assets (109 ) — (109 ) (173 ) — (173 ) Total deferred tax assets 827 26 853 1,070 22 1,092 Deferred tax liabilities: Investment securities (1 ) (340 ) (341 ) 29 (336 ) (307 ) Deferred policy acquisition costs (293 ) 91 (202 ) (448 ) 96 (352 ) Insurance claims and reserves transition liability (128 ) — (128 ) — — — Real estate, property and equipment (35 ) — (35 ) (45 ) — (45 ) Total deferred tax liabilities (457 ) (249 ) (706 ) (464 ) (240 ) (704 ) Net deferred tax asset (liability) $ 370 $ (223 ) $ 147 $ 606 $ (218 ) $ 388
Progression of the liability for uncertain tax positions, excluding interest and penalties	A progression of the liability for uncertain tax positions, excluding interest and penalties, follows (in millions): 2017 2016 2015 Balance at January 1 $ 1 $ 1 $ — Additions for tax positions of prior years — — 1 Reductions for tax positions of prior years — — — Additions for tax positions of current year — — — Settlements (1 ) — — Balance at December 31 $ — $ 1 $ 1

Quarterly Operating Results (38

Quarterly Operating Results (Unaudited) (Tables)	12 Months Ended
	Dec. 31, 2017
Quarterly Financial Information Disclosure [Abstract]
Schedule of quarterly operating results	The following are quarterly results of consolidated operations for the two years ended December 31, 2017 (in millions, except per share amounts). Quarterly earnings per share do not add to year-to-date amounts due to changes in shares outstanding. 1st Quarter 2nd Quarter 3rd Quarter 4th Quarter Total Year 2017 Revenues $ 1,576 $ 1,646 $ 1,835 $ 1,808 $ 6,865 Net earnings, including noncontrolling interests 155 145 11 166 477 Net earnings attributable to shareholders 153 145 11 166 475 Earnings attributable to shareholders per Common Share: Basic $ 1.76 $ 1.64 $ 0.13 $ 1.88 $ 5.40 Diluted 1.72 1.61 0.13 1.84 5.28 Average number of Common Shares: Basic 87.2 87.8 88.1 88.2 87.8 Diluted 89.3 89.8 90.0 90.1 89.8 2016 Revenues $ 1,475 $ 1,581 $ 1,705 $ 1,737 $ 6,498 Net earnings, including noncontrolling interests 104 63 113 388 668 Net earnings attributable to shareholders 101 54 109 385 649 Earnings attributable to shareholders per Common Share: Basic $ 1.16 $ 0.63 $ 1.25 $ 4.43 $ 7.47 Diluted 1.14 0.62 1.23 4.33 7.33 Average number of Common Shares: Basic 86.9 86.8 86.9 86.9 86.9 Diluted 88.5 88.4 88.5 88.8 88.5
Quarterly information on realized gains (losses) and favorable (unfavorable) development on unpaid loss and loss adjustment expenses	Pretax realized gains on subsidiaries and securities (including other-than-temporary impairments), favorable (adverse) prior year development of AFG’s liability for losses and loss adjustment expenses (“LAE”) and the impact of derivatives related to FIAs were as follows (in millions): 1st Quarter 2nd Quarter 3rd Quarter 4th Quarter Total Year Realized Gains (Losses) on Securities and Subsidiaries 2017 $ 3 $ 8 $ (12 ) $ 6 $ 5 2016 (18 ) (14 ) 2 51 21 Prior Year Development Favorable (Adverse) 2017 $ 28 $ 22 $ (52 ) $ 66 $ 64 2016 28 (28 ) (22 ) (10 ) (32 ) Impact of Derivatives related to Fixed-indexed Annuities 2017 $ (2 ) $ (16 ) $ (4 ) $ (11 ) $ (33 ) 2016 (31 ) (26 ) 1 29 (27 )

Insurance (Tables)

Insurance (Tables)	12 Months Ended
	Dec. 31, 2017
Insurance [Abstract]
Reconciliation of beginning and ending liability for unpaid losses and loss adjustment expenses	The following table provides an analysis of changes in the liability for losses and loss adjustment expenses over the past three years (in millions): 2017 2016 2015 Balance at beginning of period $ 8,563 $ 8,127 $ 7,872 Less reinsurance recoverables, net of allowance 2,302 2,201 2,227 Net liability at beginning of period 6,261 5,926 5,645 Provision for losses and LAE occurring in the current year 3,019 2,730 2,662 Net increase (decrease) in the provision for claims of prior years: Special A&E charges 89 36 67 Neon exited lines charge (18 ) 57 — Other (135 ) (61 ) (34 ) Total losses and LAE incurred 2,955 2,762 2,695 Payments for losses and LAE of: Current year (942 ) (841 ) (828 ) Prior years (1,586 ) (1,512 ) (1,575 ) Total payments (2,528 ) (2,353 ) (2,403 ) Reserves of businesses disposed (*) — (40 ) — Foreign currency translation and other 33 (34 ) (11 ) Net liability at end of period 6,721 6,261 5,926 Add back reinsurance recoverables, net of allowance 2,957 2,302 2,201 Gross unpaid losses and LAE included in the balance sheet $ 9,678 $ 8,563 $ 8,127 (*) Reflects the 2016 reinsurance to close transactions at Neon (discussed below).
Short-duration insurance contracts, reconciliation of claims development to liability	A reconciliation of incurred and paid claims development information to the aggregate carrying amount of the liability for unpaid losses and LAE, with separate disclosure of reinsurance recoverables on unpaid claims is shown below (in millions): 2017 Unpaid losses and allocated LAE, net of reinsurance: Specialty Property and transportation $ 1,069 Specialty casualty 3,630 Specialty financial 221 Other specialty 278 Total Specialty (excluding foreign reserves) 5,198 Other reserves Reserves for foreign operations: Neon Lloyd’s business 480 Other subsidiaries 269 A&E reserves 403 Unallocated LAE 326 Other 45 Total other reserves 1,523 Total reserves, net of reinsurance 6,721 Add back reinsurance recoverables, net of allowance 2,957 Gross unpaid losses and LAE included in the balance sheet $ 9,678
Short-duration insurance contracts, claims development	The following claims development tables and associated disclosures related to short-duration insurance contracts are prepared by sub-segment within the property and casualty insurance business for the most recent 10 accident years. AFG determines its claim counts at the claimant or policy feature level depending on the particular facts and circumstances of the underlying claim. While the methodology is generally consistent within each sub-segment, there are minor differences between and within the sub-segments. The methods used to summarize claim counts have not changed significantly over the time periods reported in the tables below. Property and transportation (Dollars in Millions) Incurred Claims and Allocated LAE, Net of Reinsurance As of December 31, 2017 For the Years Ended (2008–2016 is Supplementary Information and Unaudited) Total IBNR Plus Expected Development on Reported Claims Cumulative Number of Reported Claims Accident Year 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2008 $ 923 $ 871 $ 852 $ 853 $ 856 $ 854 $ 855 $ 856 $ 854 $ 854 $ 1 157,164 2009 526 506 523 516 511 511 508 508 508 3 140,532 2010 702 662 668 676 679 679 683 680 6 140,634 2011 830 816 831 845 856 868 865 10 140,418 2012 890 884 897 909 922 918 19 146,630 2013 911 898 902 908 910 22 142,249 2014 868 852 841 843 38 136,882 2015 842 804 798 54 135,029 2016 771 740 110 122,112 2017 913 273 128,455 Total $ 8,029 Cumulative Paid Claims and Allocated LAE, Net of Reinsurance Accident Year For the Years Ended (2008–2016 is Supplementary Information and Unaudited) 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 % (a) 2008 $ 352 $ 706 $ 761 $ 799 $ 824 $ 835 $ 846 $ 846 $ 847 $ 848 99.3 % 2009 229 348 413 456 479 493 497 499 502 98.8 % 2010 328 505 556 618 649 660 665 669 98.4 % 2011 373 679 742 787 821 840 847 97.9 % 2012 582 725 793 841 868 883 96.2 % 2013 449 721 784 831 862 94.7 % 2014 337 646 711 765 90.7 % 2015 367 595 683 85.6 % 2016 299 534 72.2 % 2017 387 42.4 % Total $ 6,980 Unpaid losses and LAE — years 2008 through 2017 1,049 Unpaid losses and LAE — 11th year and prior (excluding unallocated LAE) 20 Unpaid losses and LAE, net of reinsurance (excluding unallocated LAE) $ 1,069 Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance Year 1 Year 2 Year 3 Year 4 Year 5 Year 6 Year 7 Year 8 Year 9 Year 10 Annual 45.9 % 29.9 % 8.4 % 6.3 % 3.7 % 1.9 % 0.9 % 0.3 % 0.4 % 0.1 % Cumulative 45.9 % 75.8 % 84.2 % 90.5 % 94.2 % 96.1 % 97.0 % 97.3 % 97.7 % 97.8 % (a) Represents the cumulative percentage paid of incurred claims and allocated LAE (net of reinsurance, as estimated at December 31, 2017 ). Specialty casualty (Dollars in Millions) Incurred Claims and Allocated LAE, Net of Reinsurance As of December 31, 2017 For the Years Ended (2008–2016 is Supplementary Information and Unaudited) Total IBNR Plus Expected Development on Reported Claims Cumulative Number of Reported Claims Accident Year 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2008 $ 905 $ 891 $ 874 $ 860 $ 871 $ 856 $ 855 $ 849 $ 855 $ 854 $ 41 59,991 2009 864 867 845 826 816 811 812 807 803 48 53,192 2010 847 863 864 842 856 846 845 842 65 52,855 2011 831 831 819 828 814 808 806 73 50,851 2012 874 865 859 859 855 849 104 49,836 2013 938 921 915 910 913 132 49,412 2014 1,011 984 984 982 202 52,167 2015 1,057 1,023 1,022 268 52,846 2016 1,105 1,098 426 50,652 2017 1,186 715 46,399 Total $ 9,355 Cumulative Paid Claims and Allocated LAE, Net of Reinsurance Accident Year For the Years Ended (2008–2016 is Supplementary Information and Unaudited) 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 % (a) 2008 $ 162 $ 355 $ 490 $ 588 $ 653 $ 702 $ 727 $ 751 $ 768 $ 782 91.6 % 2009 160 366 494 575 636 673 698 713 722 89.9 % 2010 179 393 539 623 676 712 734 748 88.8 % 2011 165 369 506 595 643 674 694 86.1 % 2012 163 368 495 596 658 696 82.0 % 2013 171 377 530 638 698 76.5 % 2014 182 398 556 659 67.1 % 2015 170 398 560 54.8 % 2016 181 404 36.8 % 2017 192 16.2 % Total $ 6,155 Unpaid losses and LAE — years 2008 through 2017 3,200 Unpaid losses and LAE — 11th year and prior (excluding unallocated LAE) 430 Unpaid losses and LAE, net of reinsurance (excluding unallocated LAE) $ 3,630 Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance Year 1 Year 2 Year 3 Year 4 Year 5 Year 6 Year 7 Year 8 Year 9 Year 10 Annual 18.6 % 23.4 % 16.2 % 11.0 % 6.9 % 4.6 % 2.8 % 2.1 % 1.6 % 1.6 % Cumulative 18.6 % 42.0 % 58.2 % 69.2 % 76.1 % 80.7 % 83.5 % 85.6 % 87.2 % 88.8 % (a) Represents the cumulative percentage paid of incurred claims and allocated LAE (net of reinsurance, as estimated at December 31, 2017 ). Specialty financial (Dollars in Millions) Incurred Claims and Allocated LAE, Net of Reinsurance As of December 31, 2017 For the Years Ended (2008–2016 is Supplementary Information and Unaudited) Total IBNR Plus Expected Development on Reported Claims Cumulative Number of Reported Claims Accident Year 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2008 $ 190 $ 207 $ 212 $ 209 $ 203 $ 199 $ 198 $ 197 $ 198 $ 199 $ 1 27,292 2009 193 193 187 184 188 186 187 186 185 — 27,441 2010 139 146 133 133 135 133 130 128 2 21,929 2011 140 158 157 155 148 146 144 11 16,374 2012 164 163 151 139 137 135 11 21,050 2013 141 145 137 131 127 9 28,279 2014 146 157 156 154 16 28,983 2015 156 159 157 21 37,125 2016 179 183 26 43,484 2017 212 84 36,116 Total $ 1,624 Cumulative Paid Claims and Allocated LAE, Net of Reinsurance Accident Year For the Years Ended (2008–2016 is Supplementary Information and Unaudited) 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 % (a) 2008 $ 103 $ 153 $ 185 $ 189 $ 189 $ 191 $ 193 $ 194 $ 194 $ 197 99.0 % 2009 112 145 157 166 171 182 185 186 186 100.5 % 2010 61 93 104 122 133 131 128 127 99.2 % 2011 59 113 116 124 131 132 133 92.4 % 2012 71 104 109 117 121 126 93.3 % 2013 70 100 107 114 117 92.1 % 2014 62 108 125 128 83.1 % 2015 72 109 129 82.2 % 2016 87 141 77.0 % 2017 119 56.1 % Total $ 1,403 Unpaid losses and LAE — years 2008 through 2017 221 Unpaid losses and LAE — 11th year and prior (excluding unallocated LAE) — Unpaid losses and LAE, net of reinsurance (excluding unallocated LAE) $ 221 Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance Year 1 Year 2 Year 3 Year 4 Year 5 Year 6 Year 7 Year 8 Year 9 Year 10 Annual 49.8 % 26.3 % 8.3 % 5.7 % 3.6 % 2.0 % 0.2 % 0.1 % — % 1.5 % Cumulative 49.8 % 76.1 % 84.4 % 90.1 % 93.7 % 95.7 % 95.9 % 96.0 % 96.0 % 97.5 % (a) Represents the cumulative percentage paid of incurred claims and allocated LAE (net of reinsurance, as estimated at December 31, 2017 ). Other specialty (Dollars in Millions) Incurred Claims and Allocated LAE, Net of Reinsurance As of December 31, 2017 For the Years Ended (2008–2016 is Supplementary Information and Unaudited) Total IBNR Plus Expected Development on Reported Claims Cumulative Number of Reported Claims (a) Accident Year 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2008 $ 49 $ 49 $ 49 $ 49 $ 48 $ 46 $ 45 $ 45 $ 44 $ 43 $ 3 — 2009 41 41 41 40 37 37 36 38 33 7 — 2010 36 39 40 39 40 40 40 40 2 — 2011 39 43 42 43 43 44 44 4 — 2012 42 40 39 40 41 39 8 — 2013 46 47 46 47 50 5 — 2014 58 57 59 59 16 — 2015 59 60 63 20 — 2016 61 61 31 — 2017 63 47 — Total $ 495 Cumulative Paid Claims and Allocated LAE, Net of Reinsurance Accident Year For the Years Ended (2008–2016 is Supplementary Information and Unaudited) 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 % (b) 2008 $ 10 $ 16 $ 23 $ 31 $ 35 $ 37 $ 37 $ 37 $ 38 $ 39 90.7 % 2009 8 12 15 19 22 22 24 26 25 75.8 % 2010 8 14 21 24 27 33 35 36 90.0 % 2011 12 20 25 28 34 36 37 84.1 % 2012 8 17 21 25 28 30 76.9 % 2013 7 16 22 34 37 74.0 % 2014 13 21 30 36 61.0 % 2015 10 26 31 49.2 % 2016 9 19 31.1 % 2017 10 15.9 % Total $ 300 Unpaid losses and LAE — years 2008 through 2017 195 Unpaid losses and LAE — 11th year and prior (excluding unallocated LAE) 83 Unpaid losses and LAE, net of reinsurance (excluding unallocated LAE) $ 278 Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance Year 1 Year 2 Year 3 Year 4 Year 5 Year 6 Year 7 Year 8 Year 9 Year 10 Annual 19.8 % 17.3 % 12.5 % 12.8 % 8.9 % 5.9 % 3.3 % 2.9 % (0.4 %) 2.3 % Cumulative 19.8 % 37.1 % 49.6 % 62.4 % 71.3 % 77.2 % 80.5 % 83.4 % 83.0 % 85.3 % (a) The amounts shown in Other specialty represent business assumed by AFG’s internal reinsurance program from the operations that make up AFG’s other Specialty property and casualty insurance sub-segments. Accordingly, the liability for incurred claims and allocated LAE represents additional reserves held on claims counted in the tables provided for the other sub-segments (above). (b) Represents the cumulative percentage paid of incurred claims and allocated LAE (net of reinsurance, as estimated at December 31, 2017 ). Total Specialty Group (Dollars in Millions) Incurred Claims and Allocated LAE, Net of Reinsurance As of December 31, 2017 For the Years Ended (2008–2016 is Supplementary Information and Unaudited) Total IBNR Plus Expected Development on Reported Claims Cumulative Number of Reported Claims Accident Year 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2008 $ 2,067 $ 2,018 $ 1,987 $ 1,971 $ 1,978 $ 1,955 $ 1,953 $ 1,947 $ 1,951 $ 1,950 $ 46 244,447 2009 1,624 1,607 1,596 1,566 1,552 1,545 1,543 1,539 1,529 58 221,165 2010 1,724 1,710 1,705 1,690 1,710 1,698 1,698 1,690 75 215,418 2011 1,840 1,848 1,849 1,871 1,861 1,866 1,859 98 207,643 2012 1,970 1,952 1,946 1,947 1,955 1,941 142 217,516 2013 2,036 2,011 2,000 1,996 2,000 168 219,940 2014 2,083 2,050 2,040 2,038 272 218,032 2015 2,114 2,046 2,040 363 225,000 2016 2,116 2,082 593 216,248 2017 2,374 1,119 210,970 Total $ 19,503 Cumulative Paid Claims and Allocated LAE, Net of Reinsurance Accident Year For the Years Ended (2008–2016 is Supplementary Information and Unaudited) 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 % (a) 2008 $ 627 $ 1,230 $ 1,459 $ 1,607 $ 1,701 $ 1,765 $ 1,803 $ 1,828 $ 1,847 $ 1,866 95.7 % 2009 509 871 1,079 1,216 1,308 1,370 1,404 1,424 1,435 93.9 % 2010 576 1,005 1,220 1,387 1,485 1,536 1,562 1,580 93.5 % 2011 609 1,181 1,389 1,534 1,629 1,682 1,711 92.0 % 2012 824 1,214 1,418 1,579 1,675 1,735 89.4 % 2013 697 1,214 1,443 1,617 1,714 85.7 % 2014 594 1,173 1,422 1,588 77.9 % 2015 619 1,128 1,403 68.8 % 2016 576 1,098 52.7 % 2017 708 29.8 % Total $ 14,838 Unpaid losses and LAE — years 2008 through 2017 4,665 Unpaid losses and LAE — 11th year and prior (excluding unallocated LAE) 533 Unpaid losses and LAE, net of reinsurance (excluding unallocated LAE) $ 5,198 Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance Year 1 Year 2 Year 3 Year 4 Year 5 Year 6 Year 7 Year 8 Year 9 Year 10 Annual 32.7 % 26.1 % 12.1 % 8.5 % 5.3 % 3.3 % 1.8 % 1.2 % 0.8 % 1.0 % Cumulative 32.7 % 58.8 % 70.9 % 79.4 % 84.7 % 88.0 % 89.8 % 91.0 % 91.8 % 92.8 % (a) Represents the cumulative percentage paid of incurred claims and allocated LAE (net of reinsurance, as estimated at December 31, 2017 ).
Short-duration insurance contracts, schedule of historical claims duration	The following claims development tables and associated disclosures related to short-duration insurance contracts are prepared by sub-segment within the property and casualty insurance business for the most recent 10 accident years. AFG determines its claim counts at the claimant or policy feature level depending on the particular facts and circumstances of the underlying claim. While the methodology is generally consistent within each sub-segment, there are minor differences between and within the sub-segments. The methods used to summarize claim counts have not changed significantly over the time periods reported in the tables below. Property and transportation (Dollars in Millions) Incurred Claims and Allocated LAE, Net of Reinsurance As of December 31, 2017 For the Years Ended (2008–2016 is Supplementary Information and Unaudited) Total IBNR Plus Expected Development on Reported Claims Cumulative Number of Reported Claims Accident Year 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2008 $ 923 $ 871 $ 852 $ 853 $ 856 $ 854 $ 855 $ 856 $ 854 $ 854 $ 1 157,164 2009 526 506 523 516 511 511 508 508 508 3 140,532 2010 702 662 668 676 679 679 683 680 6 140,634 2011 830 816 831 845 856 868 865 10 140,418 2012 890 884 897 909 922 918 19 146,630 2013 911 898 902 908 910 22 142,249 2014 868 852 841 843 38 136,882 2015 842 804 798 54 135,029 2016 771 740 110 122,112 2017 913 273 128,455 Total $ 8,029 Cumulative Paid Claims and Allocated LAE, Net of Reinsurance Accident Year For the Years Ended (2008–2016 is Supplementary Information and Unaudited) 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 % (a) 2008 $ 352 $ 706 $ 761 $ 799 $ 824 $ 835 $ 846 $ 846 $ 847 $ 848 99.3 % 2009 229 348 413 456 479 493 497 499 502 98.8 % 2010 328 505 556 618 649 660 665 669 98.4 % 2011 373 679 742 787 821 840 847 97.9 % 2012 582 725 793 841 868 883 96.2 % 2013 449 721 784 831 862 94.7 % 2014 337 646 711 765 90.7 % 2015 367 595 683 85.6 % 2016 299 534 72.2 % 2017 387 42.4 % Total $ 6,980 Unpaid losses and LAE — years 2008 through 2017 1,049 Unpaid losses and LAE — 11th year and prior (excluding unallocated LAE) 20 Unpaid losses and LAE, net of reinsurance (excluding unallocated LAE) $ 1,069 Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance Year 1 Year 2 Year 3 Year 4 Year 5 Year 6 Year 7 Year 8 Year 9 Year 10 Annual 45.9 % 29.9 % 8.4 % 6.3 % 3.7 % 1.9 % 0.9 % 0.3 % 0.4 % 0.1 % Cumulative 45.9 % 75.8 % 84.2 % 90.5 % 94.2 % 96.1 % 97.0 % 97.3 % 97.7 % 97.8 % (a) Represents the cumulative percentage paid of incurred claims and allocated LAE (net of reinsurance, as estimated at December 31, 2017 ). Specialty casualty (Dollars in Millions) Incurred Claims and Allocated LAE, Net of Reinsurance As of December 31, 2017 For the Years Ended (2008–2016 is Supplementary Information and Unaudited) Total IBNR Plus Expected Development on Reported Claims Cumulative Number of Reported Claims Accident Year 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2008 $ 905 $ 891 $ 874 $ 860 $ 871 $ 856 $ 855 $ 849 $ 855 $ 854 $ 41 59,991 2009 864 867 845 826 816 811 812 807 803 48 53,192 2010 847 863 864 842 856 846 845 842 65 52,855 2011 831 831 819 828 814 808 806 73 50,851 2012 874 865 859 859 855 849 104 49,836 2013 938 921 915 910 913 132 49,412 2014 1,011 984 984 982 202 52,167 2015 1,057 1,023 1,022 268 52,846 2016 1,105 1,098 426 50,652 2017 1,186 715 46,399 Total $ 9,355 Cumulative Paid Claims and Allocated LAE, Net of Reinsurance Accident Year For the Years Ended (2008–2016 is Supplementary Information and Unaudited) 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 % (a) 2008 $ 162 $ 355 $ 490 $ 588 $ 653 $ 702 $ 727 $ 751 $ 768 $ 782 91.6 % 2009 160 366 494 575 636 673 698 713 722 89.9 % 2010 179 393 539 623 676 712 734 748 88.8 % 2011 165 369 506 595 643 674 694 86.1 % 2012 163 368 495 596 658 696 82.0 % 2013 171 377 530 638 698 76.5 % 2014 182 398 556 659 67.1 % 2015 170 398 560 54.8 % 2016 181 404 36.8 % 2017 192 16.2 % Total $ 6,155 Unpaid losses and LAE — years 2008 through 2017 3,200 Unpaid losses and LAE — 11th year and prior (excluding unallocated LAE) 430 Unpaid losses and LAE, net of reinsurance (excluding unallocated LAE) $ 3,630 Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance Year 1 Year 2 Year 3 Year 4 Year 5 Year 6 Year 7 Year 8 Year 9 Year 10 Annual 18.6 % 23.4 % 16.2 % 11.0 % 6.9 % 4.6 % 2.8 % 2.1 % 1.6 % 1.6 % Cumulative 18.6 % 42.0 % 58.2 % 69.2 % 76.1 % 80.7 % 83.5 % 85.6 % 87.2 % 88.8 % (a) Represents the cumulative percentage paid of incurred claims and allocated LAE (net of reinsurance, as estimated at December 31, 2017 ). Specialty financial (Dollars in Millions) Incurred Claims and Allocated LAE, Net of Reinsurance As of December 31, 2017 For the Years Ended (2008–2016 is Supplementary Information and Unaudited) Total IBNR Plus Expected Development on Reported Claims Cumulative Number of Reported Claims Accident Year 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2008 $ 190 $ 207 $ 212 $ 209 $ 203 $ 199 $ 198 $ 197 $ 198 $ 199 $ 1 27,292 2009 193 193 187 184 188 186 187 186 185 — 27,441 2010 139 146 133 133 135 133 130 128 2 21,929 2011 140 158 157 155 148 146 144 11 16,374 2012 164 163 151 139 137 135 11 21,050 2013 141 145 137 131 127 9 28,279 2014 146 157 156 154 16 28,983 2015 156 159 157 21 37,125 2016 179 183 26 43,484 2017 212 84 36,116 Total $ 1,624 Cumulative Paid Claims and Allocated LAE, Net of Reinsurance Accident Year For the Years Ended (2008–2016 is Supplementary Information and Unaudited) 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 % (a) 2008 $ 103 $ 153 $ 185 $ 189 $ 189 $ 191 $ 193 $ 194 $ 194 $ 197 99.0 % 2009 112 145 157 166 171 182 185 186 186 100.5 % 2010 61 93 104 122 133 131 128 127 99.2 % 2011 59 113 116 124 131 132 133 92.4 % 2012 71 104 109 117 121 126 93.3 % 2013 70 100 107 114 117 92.1 % 2014 62 108 125 128 83.1 % 2015 72 109 129 82.2 % 2016 87 141 77.0 % 2017 119 56.1 % Total $ 1,403 Unpaid losses and LAE — years 2008 through 2017 221 Unpaid losses and LAE — 11th year and prior (excluding unallocated LAE) — Unpaid losses and LAE, net of reinsurance (excluding unallocated LAE) $ 221 Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance Year 1 Year 2 Year 3 Year 4 Year 5 Year 6 Year 7 Year 8 Year 9 Year 10 Annual 49.8 % 26.3 % 8.3 % 5.7 % 3.6 % 2.0 % 0.2 % 0.1 % — % 1.5 % Cumulative 49.8 % 76.1 % 84.4 % 90.1 % 93.7 % 95.7 % 95.9 % 96.0 % 96.0 % 97.5 % (a) Represents the cumulative percentage paid of incurred claims and allocated LAE (net of reinsurance, as estimated at December 31, 2017 ). Other specialty (Dollars in Millions) Incurred Claims and Allocated LAE, Net of Reinsurance As of December 31, 2017 For the Years Ended (2008–2016 is Supplementary Information and Unaudited) Total IBNR Plus Expected Development on Reported Claims Cumulative Number of Reported Claims (a) Accident Year 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2008 $ 49 $ 49 $ 49 $ 49 $ 48 $ 46 $ 45 $ 45 $ 44 $ 43 $ 3 — 2009 41 41 41 40 37 37 36 38 33 7 — 2010 36 39 40 39 40 40 40 40 2 — 2011 39 43 42 43 43 44 44 4 — 2012 42 40 39 40 41 39 8 — 2013 46 47 46 47 50 5 — 2014 58 57 59 59 16 — 2015 59 60 63 20 — 2016 61 61 31 — 2017 63 47 — Total $ 495 Cumulative Paid Claims and Allocated LAE, Net of Reinsurance Accident Year For the Years Ended (2008–2016 is Supplementary Information and Unaudited) 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 % (b) 2008 $ 10 $ 16 $ 23 $ 31 $ 35 $ 37 $ 37 $ 37 $ 38 $ 39 90.7 % 2009 8 12 15 19 22 22 24 26 25 75.8 % 2010 8 14 21 24 27 33 35 36 90.0 % 2011 12 20 25 28 34 36 37 84.1 % 2012 8 17 21 25 28 30 76.9 % 2013 7 16 22 34 37 74.0 % 2014 13 21 30 36 61.0 % 2015 10 26 31 49.2 % 2016 9 19 31.1 % 2017 10 15.9 % Total $ 300 Unpaid losses and LAE — years 2008 through 2017 195 Unpaid losses and LAE — 11th year and prior (excluding unallocated LAE) 83 Unpaid losses and LAE, net of reinsurance (excluding unallocated LAE) $ 278 Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance Year 1 Year 2 Year 3 Year 4 Year 5 Year 6 Year 7 Year 8 Year 9 Year 10 Annual 19.8 % 17.3 % 12.5 % 12.8 % 8.9 % 5.9 % 3.3 % 2.9 % (0.4 %) 2.3 % Cumulative 19.8 % 37.1 % 49.6 % 62.4 % 71.3 % 77.2 % 80.5 % 83.4 % 83.0 % 85.3 % (a) The amounts shown in Other specialty represent business assumed by AFG’s internal reinsurance program from the operations that make up AFG’s other Specialty property and casualty insurance sub-segments. Accordingly, the liability for incurred claims and allocated LAE represents additional reserves held on claims counted in the tables provided for the other sub-segments (above). (b) Represents the cumulative percentage paid of incurred claims and allocated LAE (net of reinsurance, as estimated at December 31, 2017 ). Total Specialty Group (Dollars in Millions) Incurred Claims and Allocated LAE, Net of Reinsurance As of December 31, 2017 For the Years Ended (2008–2016 is Supplementary Information and Unaudited) Total IBNR Plus Expected Development on Reported Claims Cumulative Number of Reported Claims Accident Year 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2008 $ 2,067 $ 2,018 $ 1,987 $ 1,971 $ 1,978 $ 1,955 $ 1,953 $ 1,947 $ 1,951 $ 1,950 $ 46 244,447 2009 1,624 1,607 1,596 1,566 1,552 1,545 1,543 1,539 1,529 58 221,165 2010 1,724 1,710 1,705 1,690 1,710 1,698 1,698 1,690 75 215,418 2011 1,840 1,848 1,849 1,871 1,861 1,866 1,859 98 207,643 2012 1,970 1,952 1,946 1,947 1,955 1,941 142 217,516 2013 2,036 2,011 2,000 1,996 2,000 168 219,940 2014 2,083 2,050 2,040 2,038 272 218,032 2015 2,114 2,046 2,040 363 225,000 2016 2,116 2,082 593 216,248 2017 2,374 1,119 210,970 Total $ 19,503 Cumulative Paid Claims and Allocated LAE, Net of Reinsurance Accident Year For the Years Ended (2008–2016 is Supplementary Information and Unaudited) 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 % (a) 2008 $ 627 $ 1,230 $ 1,459 $ 1,607 $ 1,701 $ 1,765 $ 1,803 $ 1,828 $ 1,847 $ 1,866 95.7 % 2009 509 871 1,079 1,216 1,308 1,370 1,404 1,424 1,435 93.9 % 2010 576 1,005 1,220 1,387 1,485 1,536 1,562 1,580 93.5 % 2011 609 1,181 1,389 1,534 1,629 1,682 1,711 92.0 % 2012 824 1,214 1,418 1,579 1,675 1,735 89.4 % 2013 697 1,214 1,443 1,617 1,714 85.7 % 2014 594 1,173 1,422 1,588 77.9 % 2015 619 1,128 1,403 68.8 % 2016 576 1,098 52.7 % 2017 708 29.8 % Total $ 14,838 Unpaid losses and LAE — years 2008 through 2017 4,665 Unpaid losses and LAE — 11th year and prior (excluding unallocated LAE) 533 Unpaid losses and LAE, net of reinsurance (excluding unallocated LAE) $ 5,198 Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance Year 1 Year 2 Year 3 Year 4 Year 5 Year 6 Year 7 Year 8 Year 9 Year 10 Annual 32.7 % 26.1 % 12.1 % 8.5 % 5.3 % 3.3 % 1.8 % 1.2 % 0.8 % 1.0 % Cumulative 32.7 % 58.8 % 70.9 % 79.4 % 84.7 % 88.0 % 89.8 % 91.0 % 91.8 % 92.8 % (a) Represents the cumulative percentage paid of incurred claims and allocated LAE (net of reinsurance, as estimated at December 31, 2017 ).
Statutory information	Net earnings and capital and surplus on a statutory basis for the insurance subsidiaries were as follows (in millions): Net Earnings Capital and Surplus 2017 2016 2015 2017 2016 Property and casualty companies $ 484 $ 461 $ 408 $ 2,729 $ 2,939 Life insurance companies 286 167 399 2,132 1,976
Reinsurance information	The following table shows (in millions) (i) amounts deducted from property and casualty written and earned premiums in connection with reinsurance ceded, (ii) written and earned premiums included in income for reinsurance assumed and (iii) reinsurance recoveries, which represent ceded losses and loss adjustment expenses. 2017 2016 2015 Direct premiums written $ 6,310 $ 5,858 $ 5,713 Reinsurance assumed 192 123 119 Reinsurance ceded (1,751 ) (1,595 ) (1,505 ) Net written premiums $ 4,751 $ 4,386 $ 4,327 Direct premiums earned $ 6,112 $ 5,745 $ 5,613 Reinsurance assumed 157 118 105 Reinsurance ceded (1,690 ) (1,535 ) (1,494 ) Net earned premiums $ 4,579 $ 4,328 $ 4,224 Reinsurance recoveries $ 1,379 $ 810 $ 936
Schedule of reserve liabilities for annuity benefits accumulated	For certain products, the liability for “annuity benefits accumulated” includes reserves for excess benefits expected to be paid on future deaths and annuitizations (“EDAR”), guaranteed withdrawal benefits and accrued persistency and premium bonuses. The liabilities included in AFG’s Balance Sheet for these benefits, excluding the impact of unrealized gains on securities, were as follows at December 31 (in millions): 2017 2016 Expected death and annuitization $ 228 $ 223 Guaranteed withdrawal benefits 357 278 Accrued persistency and premium bonuses 3 6

Accounting Policies - Narrative

Accounting Policies - Narrative (Details) - USD ($) shares in Millions, $ in Millions		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Jan. 01, 2016	Dec. 31, 2014
Significant Accounting Policies [Line Items]
Net unrealized gain on equity securities included in AOCI		$ 840	$ 404
Impact of the U.S. corporate tax rate change on AOCI		0				$ 2
Tax benefit related to exercise of stock options		$ 18	$ 11	$ 16
Weighted average common shares adjustment related to stock-based compensation		2	1.6	1.8
Anti-dilutive potential common shares related to stock-based compensation plans		0	0.4	1.1
Maturities of short term investments		3 months
Accounting Standards Update 2014-09
Significant Accounting Policies [Line Items]
Expected effect on consolidated revenues under new revenue recognition guidance effective in 2018		2.00%
Retained Earnings
Significant Accounting Policies [Line Items]
Impact of the U.S. corporate tax rate change on AOCI		$ (145)				$ 2
Retained Earnings | Maximum
Significant Accounting Policies [Line Items]
Impact of the U.S. corporate tax rate change on AOCI					$ 1
Stock Options | Capital surplus under previous accounting guidance
Significant Accounting Policies [Line Items]
Tax benefit related to exercise of stock options		17	$ 9
Equity securities
Significant Accounting Policies [Line Items]
Net unrealized gain on equity securities included in AOCI	[1]	221	$ 98
Equity securities | Accounting Standards Update 2016-01
Significant Accounting Policies [Line Items]
Net unrealized gain on equity securities included in AOCI		221
Tax Cuts and Jobs Act of 2017 | Accounting Standards Update 2018-02
Significant Accounting Policies [Line Items]
Impact of the U.S. corporate tax rate change on AOCI		$ 145
[1]	As discussed in Note A — “Accounting Policies — Investments,” effective January 1, 2018, all equity securities currently classified as “available for sale” will be required to be carried at fair value through net earnings instead of AOCI.

Acquisitions and Sale of Busi41

Acquisitions and Sale of Businesses - Narrative on acquisitions of subsidiaries (Details) - USD ($) $ / shares in Units, $ in Millions	Nov. 10, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Business Acquisitions [Line Items]
Payments to acquire additional interest in subsidiaries				$ 0	$ 315	$ 0
Income tax expense (benefit)				247	119	195
National Interstate
Business Acquisitions [Line Items]
Percentage ownership of National Interstate by noncontrolling owners prior to acquisition	49.00%
Payments to acquire additional interest in subsidiaries	$ 315
Acquisition price per share (USD per share)	$ 32
Cash dividend paid (USD per share)	$ 0.50
Payment of special cash dividends	$ 5
Payments for acquisition related costs			$ 10
AFG
Business Acquisitions [Line Items]
Income tax expense (benefit)		$ (56)	(177)	$ 247	$ 119	$ 195
AFG | National Interstate
Business Acquisitions [Line Items]
Reduction to capital surplus	$ (137)
Income tax expense (benefit)			$ (66)

Acquisitions and Sale of Busi42

Acquisitions and Sale of Businesses - Narrative on sale of businesses (Details) $ in Millions		Dec. 24, 2015USD ($)	Mar. 31, 2015	Dec. 31, 2017USD ($)policy	Dec. 31, 2016USD ($)	Jun. 30, 2016USD ($)	Sep. 30, 2015USD ($)	Mar. 31, 2015USD ($)	Dec. 31, 2017USD ($)policy	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)	Nov. 30, 2015
Sale of Businesses
Sale of redeemable noncontrolling interests									$ (3)
Income tax expense (benefit)									247	$ 119	$ 195
Long-term care insurance reserves				$ 39	$ 37				39	37
Realized gains (losses) on subsidiaries									0	2	(161)
Property and Casualty Group
Sale of Businesses
Realized gains (losses) on subsidiaries							$ 5
Neon Capital Limited
Sale of Businesses
Sale of redeemable noncontrolling interests				(3)
Income tax expense (benefit)				(56)	(111)					(48)
AFG
Sale of Businesses
Income tax expense (benefit)				$ (56)	$ (177)				247	119	$ 195
Run-off long-term care insurance business
Sale of Businesses
Net sale proceeds	[1]	$ 13
Potential additional sale proceeds based on the release of certain statutory liabilities of the legal entities sold									$ 13
Contingent capital support agreement amount		$ 35
Contingent capital support agreement term		5 years
Long-term care insurance reserves of business sold as a percentage of total long-term care insurance reserves												96.00%
Total tax benefits proceeds from the sale of business										$ 97
Realized gains (losses) on subsidiaries		$ (166)				$ 2		$ (162)
Loss on subsidiaries, net of tax		$ (108)						$ (105)
Carrying value of the assets and liabilities of business sold as a percentage of total assets and liabilities		4.00%	4.00%
Run-off long-term care insurance business | AFG
Sale of Businesses
Number of long-term care insurance policies | policy				1,600					1,600
Long-term care insurance reserves				$ 39					$ 39
[1]	Includes the fair value of the potential additional consideration and capital maintenance agreement and is shown net of estimated expenses.

Acquisitions and Sale of Busi43

Acquisitions and Sale of Businesses - Impact of the sale of subsidiaries sold (Details) - USD ($) $ in Millions		Dec. 24, 2015	Jun. 30, 2016	Mar. 31, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Liabilities of businesses sold:
Realized gains (losses) on subsidiaries					$ 0	$ 2	$ (161)
Run-off long-term care insurance business
Sale of Businesses
Net sale proceeds	[1]	$ 13
Assets of businesses sold:
Cash and investments		1,334
Recoverables from reinsurers		630
Deferred policy acquisition costs		16
Other receivables		16
Other assets		(4)
Goodwill		2
Total assets		1,994
Liabilities of businesses sold:
Annuity benefits accumulated		261
Life, accident and health reserves		1,525
Other liabilities		7
Total liabilities		1,793
Reclassify net unrealized gain on marketable securities		22
Net assets of businesses sold		179
Realized gains (losses) on subsidiaries		(166)	$ 2	$ (162)
Tax benefit		58
Loss on subsidiaries, net of tax		$ (108)		$ (105)
[1]	Includes the fair value of the potential additional consideration and capital maintenance agreement and is shown net of estimated expenses.

Acquisitions and Sale of Busi44

Acquisitions and Sale of Businesses - Revenues, costs and expenses, and earnings before income taxes for the subsidiaries sold (Details) - Run-off long-term care insurance business $ in Millions	12 Months Ended
	Dec. 31, 2015USD ($)
Life, accident and health net earned premiums:
Long-term care	$ 73
Life operations	11
Net investment income	73
Realized gains (losses) on securities and other income	(11)
Total revenues	146
Annuity benefits	8
Life, accident and health benefits:
Long-term care	91
Life operations	11
Annuity and supplemental insurance acquisition expenses	12
Other expenses	16
Total costs and expenses	138
Earnings before income taxes	$ 8

Segments of Operations - Narrat

Segments of Operations - Narrative (Details) $ in Millions	3 Months Ended						12 Months Ended
	Dec. 31, 2017USD ($)	Sep. 30, 2017USD ($)	Jun. 30, 2017USD ($)	Mar. 31, 2017USD ($)	Sep. 30, 2016USD ($)	Jun. 30, 2016USD ($)	Dec. 31, 2017USD ($)segment	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)
Segment Reporting Information [Line Items]
Number of segments | segment							4
Revenue derived from sales of property and casualty insurance outside of the United States							5.00%	4.00%	4.00%
Property and casualty insurance | Real estate investment
Segment Reporting Information [Line Items]
Pretax income from the sale of real estate properties included in other income				$ 13		$ 32		$ 32	$ 66
Property and casualty insurance | Other lines
Segment Reporting Information [Line Items]
Special charges to increase asbestos and environmental reserves		$ 89			$ 36		$ 89	36	67
Favorable reserve development related to certain lines of business within subsidiaries in connection with a reinsurance to close agreement							18
Special charges related to the exit of certain lines of business within subsidiaries						$ 65		65
Other
Segment Reporting Information [Line Items]
Special charges to increase asbestos and environmental reserves							24	$ 5	12
Make-whole premium, settlement of interest rate swap and write off of deferred debt issuance cost included in the loss on the retirement of debt	$ 40						$ 51
Write off of deferred debt issuance cost due to the retirement of debt		$ 4	$ 7						$ 4

Segments of Operations - Assets

Segments of Operations - Assets by segment and sub-segment (Details) - USD ($) $ in Millions		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Segment Reporting Information [Line Items]
Total assets		$ 60,658	$ 55,072	$ 49,837
Property and casualty insurance
Segment Reporting Information [Line Items]
Total assets	[1]	17,171	15,574	14,689
Annuity
Segment Reporting Information [Line Items]
Total assets		37,179	33,409	29,865
Run-off long-term care and life
Segment Reporting Information [Line Items]
Total assets		730	752	772
Other
Segment Reporting Information [Line Items]
Total assets		$ 5,578	$ 5,337	$ 4,511
[1]	Not allocable to sub-segments.

Segments of Operations - Revenu

Segments of Operations - Revenues by segment and sub-segment (Details) - USD ($) $ in Millions		3 Months Ended								12 Months Ended
		Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Segment Reporting Information [Line Items]
Total premiums earned										$ 4,579	$ 4,328	$ 4,224
Net investment income										1,831	1,696	1,633
Other income										206	224	243
Revenues before realized gains (losses)										6,860	6,477	6,325
Realized gains (losses) on securities										5	19	(19)
Realized gains (losses) on subsidiaries										0	2	(161)
Total revenues		$ 1,808	$ 1,835	$ 1,646	$ 1,576	$ 1,737	$ 1,705	$ 1,581	$ 1,475	6,865	6,498	6,145
Property and casualty insurance
Segment Reporting Information [Line Items]
Total premiums earned										4,579	4,328	4,224
Net investment income										362	350	319
Other income	[1]									28	51	78
Revenues before realized gains (losses)										4,969	4,729	4,621
Annuity
Segment Reporting Information [Line Items]
Net investment income										1,458	1,356	1,224
Other income										103	103	98
Revenues before realized gains (losses)										1,561	1,459	1,322
Run-off long-term care and life
Segment Reporting Information [Line Items]
Revenues before realized gains (losses)	[2]									47	49	188
Other
Segment Reporting Information [Line Items]
Revenues before realized gains (losses)										283	240	194
Property and transportation | Property and casualty insurance
Segment Reporting Information [Line Items]
Total premiums earned										1,711	1,662	1,599
Specialty casualty | Property and casualty insurance
Segment Reporting Information [Line Items]
Total premiums earned										2,186	2,006	2,011
Specialty financial | Property and casualty insurance
Segment Reporting Information [Line Items]
Total premiums earned										576	557	517
Other specialty | Property and casualty insurance
Segment Reporting Information [Line Items]
Total premiums earned										$ 106	$ 103	$ 97
[1]	Includes income of $32 million (before noncontrolling interest) from the sale of an apartment property in 2016 and $66 million (before noncontrolling interest) from the sales of a hotel and an apartment property in 2015.
[2]	AFG sold substantially all of its run-off long-term care insurance business in December 2015.

Segments of Operations - Earnin

Segments of Operations - Earnings before income taxes by segment and sub-segment (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Segment Reporting Information [Line Items]
Earnings before realized gains (losses) and income taxes		$ 719	$ 766	$ 745
Realized gains (losses) on securities		5	19	(19)
Realized gains (losses) on subsidiaries		0	2	(161)
Earnings before income taxes		724	787	565
Property and casualty insurance
Segment Reporting Information [Line Items]
Property and casualty insurance underwriting		242	236	225
Investment and other income, net	[1]	349	341	351
Earnings before realized gains (losses) and income taxes		591	577	576
Annuity
Segment Reporting Information [Line Items]
Earnings before realized gains (losses) and income taxes		380	368	331
Run-off long-term care and life
Segment Reporting Information [Line Items]
Earnings before realized gains (losses) and income taxes	[2]	6	2	14
Other
Segment Reporting Information [Line Items]
Earnings before realized gains (losses) and income taxes	[3]	(258)	(181)	(176)
Property and transportation | Property and casualty insurance
Segment Reporting Information [Line Items]
Property and casualty insurance underwriting		154	166	48
Specialty casualty | Property and casualty insurance
Segment Reporting Information [Line Items]
Property and casualty insurance underwriting		104	78	146
Specialty financial | Property and casualty insurance
Segment Reporting Information [Line Items]
Property and casualty insurance underwriting		61	84	87
Other specialty | Property and casualty insurance
Segment Reporting Information [Line Items]
Property and casualty insurance underwriting		(2)	9	14
Other lines | Property and casualty insurance
Segment Reporting Information [Line Items]
Property and casualty insurance underwriting	[4]	$ (75)	$ (101)	$ (70)
[1]	Includes income of $32 million (before noncontrolling interest) from the sale of an apartment property in 2016 and $66 million (before noncontrolling interest) from the sales of a hotel and an apartment property in 2015.
[2]	AFG sold substantially all of its run-off long-term care insurance business in December 2015.
[3]	Primarily holding company interest and expenses, including losses on retirement of debt of $51 million in 2017 and $4 million in 2015, and special charges to increase A&E reserves related to AFG’s former railroad and manufacturing operations ($24 million in 2017, $5 million in 2016 and $12 million in 2015).
[4]	Includes special charges to increase asbestos and environmental (“A&E”) reserves of $89 million, $36 million and $67 million in 2017, 2016 and 2015, respectively. Also includes $18 million in favorable development related to the Neon exited lines recorded in connection with a reinsurance to close transaction in 2017 and a charge of $65 million related to Neon exited lines in 2016.

Fair Value Measurements - Narra

Fair Value Measurements - Narrative (Details) $ in Millions		Dec. 24, 2015USD ($)	Dec. 31, 2017USD ($)professional	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)
Fair Value Measurements (Textual) [Abstract]
AFG's internal investment professionals | professional			25
Level 3 assets as a percentage of total assets measured at fair value			5.00%
Percentage of level 3 assets that were priced using non-binding broker quotes			79.00%
Level 3 assets that were priced using non-binding broker quotes			$ 1,800
Life contingent annuities			$ 206	$ 204
Maximum
Fair Value Measurements (Textual) [Abstract]
Percentage of internally developed Level 3 asset fair values to Shareholders' equity (are less than)			10.00%
Fixed-indexed annuities (embedded derivative)
Fair Value Measurements (Textual) [Abstract]
Fair value of derivatives in annuity benefits accumulated measured using a discounted cash flow approach			$ 2,540
Fixed-indexed annuities (embedded derivative) | Minimum
Fair Value Measurements (Textual) [Abstract]
Unobservable input surrenders used in Level 3 fair value determination			3.00%
Fixed-indexed annuities (embedded derivative) | Maximum
Fair Value Measurements (Textual) [Abstract]
Unobservable input surrenders used in Level 3 fair value determination			23.00%
Fixed-indexed annuities (embedded derivative), majority of future years | Minimum
Fair Value Measurements (Textual) [Abstract]
Unobservable input surrenders used in Level 3 fair value determination			6.00%
Fixed-indexed annuities (embedded derivative), majority of future years | Maximum
Fair Value Measurements (Textual) [Abstract]
Unobservable input surrenders used in Level 3 fair value determination			10.00%
Not Designated as Hedging Instrument | Annuity benefits | Fixed-indexed annuities (embedded derivative)
Fair Value Measurements (Textual) [Abstract]
Total realized/unrealized gains (losses) included in net income for the embedded derivatives related to the unlocking of actuarial assumptions			$ (25)	$ (17)	$ (28)
Run-off long-term care insurance business
Fair Value Measurements (Textual) [Abstract]
Net sale proceeds of the run-off long-term care insurance business	[1]	$ 13
[1]	Includes the fair value of the potential additional consideration and capital maintenance agreement and is shown net of estimated expenses.

Fair Value Measurements - Asset

Fair Value Measurements - Assets and liabilities measured and carried at fair value in the financial statements (Details) - USD ($) $ in Millions		Dec. 31, 2017	Dec. 31, 2016
Assets:
Available for sale (AFS) fixed maturities		$ 38,379	$ 34,544
Trading fixed maturities		348	359
Assets of managed investment entities (MIE)		4,902	4,765
Variable annuity assets (separate accounts)	[1]	644	600
Derivatives including equity index call options and other assets		701	492
Total assets accounted for at fair value		46,636	42,319
Liabilities:
Liabilities of managed investment entities		4,687	4,549
Total liabilities accounted for at fair value		7,264	6,337
Derivatives in annuity benefits accumulated
Liabilities:
Derivatives included in annuity benefits accumulated, long-term debt, and other liabilities		2,542	1,759
Derivatives in long-term debt
Liabilities:
Derivatives included in annuity benefits accumulated, long-term debt, and other liabilities			(1)
Other liabilities — derivatives
Liabilities:
Derivatives included in annuity benefits accumulated, long-term debt, and other liabilities		35	30
Fixed maturities
Assets:
Available for sale (AFS) fixed maturities		38,379	34,544
Trading fixed maturities		348	359
U.S. Government and government agencies
Assets:
Available for sale (AFS) fixed maturities		242	315
States, municipalities and political subdivisions
Assets:
Available for sale (AFS) fixed maturities		7,123	6,781
Foreign government
Assets:
Available for sale (AFS) fixed maturities		127	136
Residential MBS
Assets:
Available for sale (AFS) fixed maturities		3,227	3,635
Commercial MBS
Assets:
Available for sale (AFS) fixed maturities		962	1,493
Asset-backed securities (“ABS”)
Assets:
Available for sale (AFS) fixed maturities		7,962	5,959
Corporate and other
Assets:
Available for sale (AFS) fixed maturities		18,736	16,225
Equity securities
Assets:
Equity securities — AFS and trading		1,662	1,558
Other assets — derivatives
Assets:
Derivatives including equity index call options and other assets		0	1
Level 1
Assets:
Assets of managed investment entities (MIE)		307	380
Variable annuity assets (separate accounts)	[1]	0	0
Total assets accounted for at fair value		1,914	1,877
Liabilities:
Liabilities of managed investment entities		293	363
Total liabilities accounted for at fair value		293	363
Level 1 | Derivatives in annuity benefits accumulated
Liabilities:
Derivatives included in annuity benefits accumulated, long-term debt, and other liabilities		0	0
Level 1 | Derivatives in long-term debt
Liabilities:
Derivatives included in annuity benefits accumulated, long-term debt, and other liabilities			0
Level 1 | Other liabilities — derivatives
Liabilities:
Derivatives included in annuity benefits accumulated, long-term debt, and other liabilities		0	0
Level 1 | Fixed maturities
Assets:
Available for sale (AFS) fixed maturities		152	162
Trading fixed maturities		44	30
Level 1 | U.S. Government and government agencies
Assets:
Available for sale (AFS) fixed maturities		122	133
Level 1 | States, municipalities and political subdivisions
Assets:
Available for sale (AFS) fixed maturities		0	0
Level 1 | Foreign government
Assets:
Available for sale (AFS) fixed maturities		0	0
Level 1 | Residential MBS
Assets:
Available for sale (AFS) fixed maturities		0	0
Level 1 | Commercial MBS
Assets:
Available for sale (AFS) fixed maturities		0	0
Level 1 | Asset-backed securities (“ABS”)
Assets:
Available for sale (AFS) fixed maturities		0	0
Level 1 | Corporate and other
Assets:
Available for sale (AFS) fixed maturities		30	29
Level 1 | Equity securities
Assets:
Equity securities — AFS and trading		1,411	1,305
Level 1 | Other assets — derivatives
Assets:
Derivatives including equity index call options and other assets		0	0
Level 2
Assets:
Assets of managed investment entities (MIE)		4,572	4,356
Variable annuity assets (separate accounts)	[1]	644	600
Total assets accounted for at fair value		42,432	38,680
Liabilities:
Liabilities of managed investment entities		4,372	4,158
Total liabilities accounted for at fair value		4,407	4,187
Level 2 | Derivatives in annuity benefits accumulated
Liabilities:
Derivatives included in annuity benefits accumulated, long-term debt, and other liabilities		0	0
Level 2 | Derivatives in long-term debt
Liabilities:
Derivatives included in annuity benefits accumulated, long-term debt, and other liabilities			(1)
Level 2 | Other liabilities — derivatives
Liabilities:
Derivatives included in annuity benefits accumulated, long-term debt, and other liabilities		35	30
Level 2 | Fixed maturities
Assets:
Available for sale (AFS) fixed maturities		36,125	32,823
Trading fixed maturities		304	329
Level 2 | U.S. Government and government agencies
Assets:
Available for sale (AFS) fixed maturities		112	174
Level 2 | States, municipalities and political subdivisions
Assets:
Available for sale (AFS) fixed maturities		6,975	6,641
Level 2 | Foreign government
Assets:
Available for sale (AFS) fixed maturities		127	136
Level 2 | Residential MBS
Assets:
Available for sale (AFS) fixed maturities		3,105	3,445
Level 2 | Commercial MBS
Assets:
Available for sale (AFS) fixed maturities		926	1,468
Level 2 | Asset-backed securities (“ABS”)
Assets:
Available for sale (AFS) fixed maturities		7,218	5,475
Level 2 | Corporate and other
Assets:
Available for sale (AFS) fixed maturities		17,662	15,484
Level 2 | Equity securities
Assets:
Equity securities — AFS and trading		86	79
Level 2 | Other assets — derivatives
Assets:
Derivatives including equity index call options and other assets		0	1
Level 3
Assets:
Assets of managed investment entities (MIE)		23	29
Variable annuity assets (separate accounts)	[1]	0	0
Total assets accounted for at fair value		2,290	1,762
Liabilities:
Liabilities of managed investment entities		22	28
Total liabilities accounted for at fair value		2,564	1,787
Level 3 | Derivatives in annuity benefits accumulated
Liabilities:
Derivatives included in annuity benefits accumulated, long-term debt, and other liabilities		2,542	1,759
Level 3 | Derivatives in long-term debt
Liabilities:
Derivatives included in annuity benefits accumulated, long-term debt, and other liabilities			0
Level 3 | Other liabilities — derivatives
Liabilities:
Derivatives included in annuity benefits accumulated, long-term debt, and other liabilities		0	0
Level 3 | Fixed maturities
Assets:
Available for sale (AFS) fixed maturities		2,102	1,559
Trading fixed maturities		0	0
Level 3 | U.S. Government and government agencies
Assets:
Available for sale (AFS) fixed maturities		8	8
Level 3 | States, municipalities and political subdivisions
Assets:
Available for sale (AFS) fixed maturities		148	140
Level 3 | Foreign government
Assets:
Available for sale (AFS) fixed maturities		0	0
Level 3 | Residential MBS
Assets:
Available for sale (AFS) fixed maturities		122	190
Level 3 | Commercial MBS
Assets:
Available for sale (AFS) fixed maturities		36	25
Level 3 | Asset-backed securities (“ABS”)
Assets:
Available for sale (AFS) fixed maturities		744	484
Level 3 | Corporate and other
Assets:
Available for sale (AFS) fixed maturities		1,044	712
Level 3 | Equity securities
Assets:
Equity securities — AFS and trading		165	174
Level 3 | Other assets — derivatives
Assets:
Derivatives including equity index call options and other assets		0	0
Equity index call options | Equity index call options
Assets:
Derivatives including equity index call options and other assets		701	492
Equity index call options | Level 1 | Equity index call options
Assets:
Derivatives including equity index call options and other assets		0	0
Equity index call options | Level 2 | Equity index call options
Assets:
Derivatives including equity index call options and other assets		701	492
Equity index call options | Level 3 | Equity index call options
Assets:
Derivatives including equity index call options and other assets		$ 0	$ 0
[1]	Variable annuity liabilities equal the fair value of variable annuity assets.

Fair Value Measurements - Trans

Fair Value Measurements - Transfers between Level 1 and Level 2 (Details) $ in Millions	Dec. 31, 2017USD ($)stock	Dec. 31, 2016USD ($)stock	Dec. 31, 2015USD ($)stock
Perpetual preferred stocks
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Number of stocks transferred from Level 2 to Level 1 | stock	4	6	5
Fair value of assets transferred from Level 2 to Level 1 | $	$ 23	$ 35	$ 19
Number of stocks transferred from Level 1 to Level 2 | stock	2	7	7
Fair value of assets transferred from Level 1 to Level 2 | $	$ 11	$ 28	$ 31
Common stocks
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Number of stocks transferred from Level 2 to Level 1 | stock	0	3	7
Fair value of assets transferred from Level 2 to Level 1 | $	$ 0	$ 0	$ 80
Number of stocks transferred from Level 1 to Level 2 | stock	1	2	0
Fair value of assets transferred from Level 1 to Level 2 | $	$ 0	$ 0	$ 0
Redeemable preferred stocks
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Number of stocks transferred from Level 2 to Level 1 | stock	0	0	2
Fair value of assets transferred from Level 2 to Level 1 | $	$ 0	$ 0	$ 11
Number of stocks transferred from Level 1 to Level 2 | stock	0	0	0
Fair value of assets transferred from Level 1 to Level 2 | $	$ 0	$ 0	$ 0

Fair Value Measurements - Unobs

Fair Value Measurements - Unobservable inputs used in determining fair value of embedded derivatives (Details) - Embedded derivatives	12 Months Ended
	Dec. 31, 2017
Unobservable inputs used by management in determining fair value of embedded derivatives
Risk margin for uncertainty in cash flows	0.70%
Minimum
Unobservable inputs used by management in determining fair value of embedded derivatives
Adjustment for insurance subsidiary's credit risk	0.20%
Surrenders	3.00%
Partial surrenders	2.00%
Annuitizations	0.10%
Deaths	1.60%
Budgeted option costs	2.40%
Maximum
Unobservable inputs used by management in determining fair value of embedded derivatives
Adjustment for insurance subsidiary's credit risk	2.00%
Surrenders	23.00%
Partial surrenders	10.00%
Annuitizations	1.00%
Deaths	8.00%
Budgeted option costs	3.60%

Fair Value Measurements - Chang

Fair Value Measurements - Changes in balances of Level 3 financial assets carried at fair value (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Financial assets, Beginning Balance	$ 1,762	$ 1,636	$ 1,355
Impact of accounting change			0
Total realized/unrealized gains (losses) included in Net earnings	(39)	(35)	(31)
Total realized/unrealized gains (losses) included in other comprehensive income (loss)	17	21	(28)
Purchases and issuances	1,079	347	543
Sales and settlements	(437)	(217)	(183)
Transfer into Level 3	289	139	186
Transfer out of Level 3	(381)	(129)	(160)
Sale of subsidiaries			(46)
Financial assets, Ending Balance	2,290	1,762	1,636
Fixed maturities
Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Financial assets, Beginning Balance	1,559	1,470	1,231
Impact of accounting change			0
Total realized/unrealized gains (losses) included in Net earnings	(7)	(14)	(16)
Total realized/unrealized gains (losses) included in other comprehensive income (loss)	7	(14)	(19)
Purchases and issuances	1,032	291	460
Sales and settlements	(421)	(189)	(183)
Transfer into Level 3	289	124	186
Transfer out of Level 3	(357)	(109)	(143)
Sale of subsidiaries			(46)
Financial assets, Ending Balance	2,102	1,559	1,470
U.S. government agency
Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Financial assets, Beginning Balance	8	15	15
Impact of accounting change			0
Total realized/unrealized gains (losses) included in Net earnings	0	(8)	0
Total realized/unrealized gains (losses) included in other comprehensive income (loss)	0	1	0
Purchases and issuances	0	0	0
Sales and settlements	0	0	0
Transfer into Level 3	0	0	0
Transfer out of Level 3	0	0	0
Sale of subsidiaries			0
Financial assets, Ending Balance	8	8	15
State and municipal
Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Financial assets, Beginning Balance	140	89	100
Impact of accounting change			0
Total realized/unrealized gains (losses) included in Net earnings	0	0	0
Total realized/unrealized gains (losses) included in other comprehensive income (loss)	2	(4)	(1)
Purchases and issuances	0	57	34
Sales and settlements	(2)	(2)	(1)
Transfer into Level 3	10	0	2
Transfer out of Level 3	(2)	0	(39)
Sale of subsidiaries			(6)
Financial assets, Ending Balance	148	140	89
Residential MBS
Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Financial assets, Beginning Balance	190	224	300
Impact of accounting change			0
Total realized/unrealized gains (losses) included in Net earnings	(4)	(4)	(11)
Total realized/unrealized gains (losses) included in other comprehensive income (loss)	2	(2)	(1)
Purchases and issuances	1	8	0
Sales and settlements	(40)	(28)	(34)
Transfer into Level 3	44	34	86
Transfer out of Level 3	(71)	(42)	(88)
Sale of subsidiaries			(28)
Financial assets, Ending Balance	122	190	224
Commercial MBS
Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Financial assets, Beginning Balance	25	39	44
Impact of accounting change			0
Total realized/unrealized gains (losses) included in Net earnings	2	(1)	(1)
Total realized/unrealized gains (losses) included in other comprehensive income (loss)	0	0	(1)
Purchases and issuances	15	0	0
Sales and settlements	(10)	(7)	(2)
Transfer into Level 3	4	0	4
Transfer out of Level 3	0	(6)	(1)
Sale of subsidiaries			(4)
Financial assets, Ending Balance	36	25	39
Asset-backed securities
Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Financial assets, Beginning Balance	484	470	226
Impact of accounting change			0
Total realized/unrealized gains (losses) included in Net earnings	0	(1)	1
Total realized/unrealized gains (losses) included in other comprehensive income (loss)	1	1	(7)
Purchases and issuances	410	50	265
Sales and settlements	(132)	(52)	(56)
Transfer into Level 3	202	60	53
Transfer out of Level 3	(221)	(44)	(10)
Sale of subsidiaries			(2)
Financial assets, Ending Balance	744	484	470
Corporate and other
Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Financial assets, Beginning Balance	712	633	546
Impact of accounting change			0
Total realized/unrealized gains (losses) included in Net earnings	(5)	0	(5)
Total realized/unrealized gains (losses) included in other comprehensive income (loss)	2	(10)	(9)
Purchases and issuances	606	176	161
Sales and settlements	(237)	(100)	(90)
Transfer into Level 3	29	30	41
Transfer out of Level 3	(63)	(17)	(5)
Sale of subsidiaries			(6)
Financial assets, Ending Balance	1,044	712	633
Equity securities
Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Financial assets, Beginning Balance	174	140	93
Impact of accounting change			0
Total realized/unrealized gains (losses) included in Net earnings	(21)	(12)	(4)
Total realized/unrealized gains (losses) included in other comprehensive income (loss)	10	35	(9)
Purchases and issuances	38	44	77
Sales and settlements	(16)	(28)	0
Transfer into Level 3	0	15	0
Transfer out of Level 3	(20)	(20)	(17)
Sale of subsidiaries			0
Financial assets, Ending Balance	165	174	140
Assets of MIE
Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Financial assets, Beginning Balance	29	26	31
Impact of accounting change			0
Total realized/unrealized gains (losses) included in Net earnings	(11)	(9)	(11)
Total realized/unrealized gains (losses) included in other comprehensive income (loss)	0	0	0
Purchases and issuances	9	12	6
Sales and settlements	0	0	0
Transfer into Level 3	0	0	0
Transfer out of Level 3	(4)	0	0
Sale of subsidiaries			0
Financial assets, Ending Balance	$ 23	$ 29	$ 26

Fair Value Measurements - Cha54

Fair Value Measurements - Changes in balances of Level 3 financial liabilities carried at fair value (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2017		Dec. 31, 2016		Dec. 31, 2015
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Financial liabilities, Beginning Balance		$ (1,759)	[1]	$ (1,369)		$ (3,861)
Impact of accounting change						2,701
Total realized/unrealized gains (losses) included in Net earnings		(589)		(211)		(17)
Total realized/unrealized gains (losses) included in other comprehensive income (loss)		0		0		0
Purchases and issuances		(300)		(277)		(257)
Sales and settlements		106		98		65
Transfer into Level 3		0		0		0
Transfer out of Level 3		0		0		0
Sale of subsidiaries						0
Financial liabilities, Ending Balance		(2,542)	[2]	(1,759)	[1]	(1,369)
Liabilities of MIE
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Financial liabilities, Beginning Balance				0		(2,701)
Impact of accounting change	[3]					2,701
Total realized/unrealized gains (losses) included in Net earnings						0
Total realized/unrealized gains (losses) included in other comprehensive income (loss)						0
Purchases and issuances						0
Sales and settlements						0
Transfer into Level 3						0
Transfer out of Level 3						0
Sale of subsidiaries						0
Financial liabilities, Ending Balance						0
Embedded derivatives
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Financial liabilities, Beginning Balance		(1,759)		(1,369)		(1,160)
Impact of accounting change						0
Total realized/unrealized gains (losses) included in Net earnings		(589)	[4]	(211)	[5]	(17)	[6]
Total realized/unrealized gains (losses) included in other comprehensive income (loss)		0		0		0
Purchases and issuances		(300)		(277)		(257)
Sales and settlements		106		98		65
Transfer into Level 3		0		0		0
Transfer out of Level 3		0		0		0
Sale of subsidiaries						0
Financial liabilities, Ending Balance		$ (2,542)		$ (1,759)		$ (1,369)
[1]	As previously discussed, these tables exclude the portion of MIE liabilities allocated to Level 3, which are derived from the fair value of the MIE assets.
[2]	As previously discussed, these tables exclude the portion of MIE liabilities allocated to Level 3, which are derived from the fair value of the MIE assets.
[3]	The impact of implementing new guidance adopted in 2015, as discussed in Note A — “Accounting Policies — Managed Investment Entities.”
[4]	Total realized/unrealized gains (losses) included in net earnings for the embedded derivatives reflects losses related to the unlocking of actuarial assumptions of $25 million in 2017.
[5]	Total realized/unrealized gains (losses) included in net earnings for the embedded derivatives reflects losses related to the unlocking of actuarial assumptions of $17 million in 2016.
[6]	Total realized/unrealized gains (losses) included in net earnings for the embedded derivatives reflects losses related to the unlocking of actuarial assumptions of $28 million in 2015.

Fair Value Measurements - The c

Fair Value Measurements - The carrying value and fair value of financial instruments (Details) - USD ($) $ in Millions		Dec. 31, 2017	Dec. 31, 2016
Financial assets:
Mortgage loans		$ 1,125	$ 1,147
Policy loans		184	192
Financial liabilities:
Long-term debt		1,301	1,283
Level 1
Financial assets:
Cash and cash equivalents		2,338	2,107
Mortgage loans		0	0
Policy loans		0	0
Total financial assets not accounted for at fair value		2,338	2,107
Financial liabilities:
Annuity benefits accumulated	[1]	0	0
Long-term debt		0	0
Total financial liabilities not accounted for at fair value		0	0
Level 2
Financial assets:
Cash and cash equivalents		0	0
Mortgage loans		0	0
Policy loans		0	0
Total financial assets not accounted for at fair value		0	0
Financial liabilities:
Annuity benefits accumulated	[1]	0	0
Long-term debt		1,351	1,353
Total financial liabilities not accounted for at fair value		1,351	1,353
Level 3
Financial assets:
Cash and cash equivalents		0	0
Mortgage loans		1,119	1,146
Policy loans		184	192
Total financial assets not accounted for at fair value		1,303	1,338
Financial liabilities:
Annuity benefits accumulated	[1]	32,461	28,932
Long-term debt		3	3
Total financial liabilities not accounted for at fair value		32,464	28,935
Carrying Value
Financial assets:
Cash and cash equivalents		2,338	2,107
Mortgage loans		1,125	1,147
Policy loans		184	192
Total financial assets not accounted for at fair value		3,647	3,446
Financial liabilities:
Annuity benefits accumulated	[1]	33,110	29,703
Long-term debt		1,301	1,284
Total financial liabilities not accounted for at fair value		34,411	30,987
Fair Value
Financial assets:
Cash and cash equivalents		2,338	2,107
Mortgage loans		1,119	1,146
Policy loans		184	192
Total financial assets not accounted for at fair value		3,641	3,445
Financial liabilities:
Annuity benefits accumulated	[1]	32,461	28,932
Long-term debt		1,354	1,356
Total financial liabilities not accounted for at fair value		$ 33,815	$ 30,288
[1]	Excludes $206 million and $204 million of life contingent annuities in the payout phase at December 31, 2017 and 2016, respectively.

Investments - Narrative (Detail

Investments - Narrative (Details) $ in Millions	12 Months Ended
	Dec. 31, 2017USD ($)security	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)
Investment [Line Items]
Percentage (based on amount of unrealized loss) of available for sale fixed maturities that are in an unrealized loss position and rated investment grade	78.00%
Percentage (based on fair value) of available for sale fixed maturities that are in an unrealized loss position and rated investment grade	90.00%
Other than temporary impairment charges	$ 73	$ 116	$ 125
Average life of ABS	5 years
Average life of MBS	4 years 6 months
Residential MBS
Investment [Line Items]
Non-credit related portion of other-than-temporary impairment charges taken for securities still owned	$ 158	189
Fixed maturities, Gross Unrealized, Losses	(6)	(13)
Other than temporary impairment charges	1
Fixed Maturities excluding Residential MBS
Investment [Line Items]
Other than temporary impairment charges	19
Securities with non-credit other-than-temporary impairment charges
Investment [Line Items]
Gross Unrealized, Gains	137	130
Gross Unrealized, Losses	(4)	(3)
Fixed maturities
Investment [Line Items]
Fixed maturities, Gross Unrealized, Losses	$ (82)	(245)
Number of available for sale securities in an unrealized loss position | security	841
Other than temporary impairment charges	$ 20	38	$ 43
Other investments
Investment [Line Items]
Other than temporary impairment charges	$ 4
Common stocks
Investment [Line Items]
Number of available for sale securities in an unrealized loss position | security	16
Other than temporary impairment charges	$ 55
Equity securities, Gross Unrealized, Losses	$ (22)	(23)
Preferred stocks
Investment [Line Items]
Number of available for sale securities in an unrealized loss position | security	7
Other than temporary impairment charges	$ 9
Equity securities, Gross Unrealized, Losses	$ (1)	$ (7)
Number of available for sale securities in an unrealized loss position for twelve months or longer | Common stocks
Investment [Line Items]
Number of available for sale securities in an unrealized loss position | security	0
Number of available for sale securities in an unrealized loss position for twelve months or longer | Preferred stocks
Investment [Line Items]
Number of available for sale securities in an unrealized loss position | security	3

Investments - Available for sal

Investments - Available for sale fixed maturities and equity securities (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Schedule of Available-for-sale Securities [Line Items]
Fixed maturities, Available for sale, Amortized Cost	$ 37,038	$ 33,735
Available for sale (AFS) fixed maturities	38,379	34,544
Equity securities, Available for sale, Amortized Cost	1,321	1,351
Equity securities, Available for sale, Fair Value	1,600	1,502
Total fixed maturities
Schedule of Available-for-sale Securities [Line Items]
Fixed maturities, Available for sale, Amortized Cost	37,038	33,735
Fixed maturities, Available for sale, Gross Unrealized, Gains	1,423	1,054
Fixed maturities, Available for sale, Gross Unrealized, Losses	(82)	(245)
Fixed maturities, Available for sale, Net Unrealized, Gains (Losses)	1,341	809
Available for sale (AFS) fixed maturities	38,379	34,544
U.S. Government and government agencies
Schedule of Available-for-sale Securities [Line Items]
Fixed maturities, Available for sale, Amortized Cost	244	315
Fixed maturities, Available for sale, Gross Unrealized, Gains	1	3
Fixed maturities, Available for sale, Gross Unrealized, Losses	(3)	(3)
Fixed maturities, Available for sale, Net Unrealized, Gains (Losses)	(2)	0
Available for sale (AFS) fixed maturities	242	315
States, municipalities and political subdivisions
Schedule of Available-for-sale Securities [Line Items]
Fixed maturities, Available for sale, Amortized Cost	6,887	6,650
Fixed maturities, Available for sale, Gross Unrealized, Gains	254	200
Fixed maturities, Available for sale, Gross Unrealized, Losses	(18)	(69)
Fixed maturities, Available for sale, Net Unrealized, Gains (Losses)	236	131
Available for sale (AFS) fixed maturities	7,123	6,781
Foreign government
Schedule of Available-for-sale Securities [Line Items]
Fixed maturities, Available for sale, Amortized Cost	124	131
Fixed maturities, Available for sale, Gross Unrealized, Gains	3	5
Fixed maturities, Available for sale, Gross Unrealized, Losses	0	0
Fixed maturities, Available for sale, Net Unrealized, Gains (Losses)	3	5
Available for sale (AFS) fixed maturities	127	136
Residential MBS
Schedule of Available-for-sale Securities [Line Items]
Fixed maturities, Available for sale, Amortized Cost	2,884	3,367
Fixed maturities, Available for sale, Gross Unrealized, Gains	349	281
Fixed maturities, Available for sale, Gross Unrealized, Losses	(6)	(13)
Fixed maturities, Available for sale, Net Unrealized, Gains (Losses)	343	268
Available for sale (AFS) fixed maturities	3,227	3,635
Commercial MBS
Schedule of Available-for-sale Securities [Line Items]
Fixed maturities, Available for sale, Amortized Cost	927	1,446
Fixed maturities, Available for sale, Gross Unrealized, Gains	36	49
Fixed maturities, Available for sale, Gross Unrealized, Losses	(1)	(2)
Fixed maturities, Available for sale, Net Unrealized, Gains (Losses)	35	47
Available for sale (AFS) fixed maturities	962	1,493
Asset-backed securities
Schedule of Available-for-sale Securities [Line Items]
Fixed maturities, Available for sale, Amortized Cost	7,836	5,962
Fixed maturities, Available for sale, Gross Unrealized, Gains	142	43
Fixed maturities, Available for sale, Gross Unrealized, Losses	(16)	(46)
Fixed maturities, Available for sale, Net Unrealized, Gains (Losses)	126	(3)
Available for sale (AFS) fixed maturities	7,962	5,959
Corporate and other
Schedule of Available-for-sale Securities [Line Items]
Fixed maturities, Available for sale, Amortized Cost	18,136	15,864
Fixed maturities, Available for sale, Gross Unrealized, Gains	638	473
Fixed maturities, Available for sale, Gross Unrealized, Losses	(38)	(112)
Fixed maturities, Available for sale, Net Unrealized, Gains (Losses)	600	361
Available for sale (AFS) fixed maturities	18,736	16,225
Total equity securities
Schedule of Available-for-sale Securities [Line Items]
Equity securities, Available for sale, Amortized Cost	1,321	1,351
Equity securities, Available for sale, Gross Unrealized, Gains	302	181
Equity securities, Available for sale, Gross Unrealized, Losses	(23)	(30)
Equity securities, Available for sale, Net Unrealized, Gains (Losses)	279	151
Equity securities, Available for sale, Fair Value	1,600	1,502
Common stocks
Schedule of Available-for-sale Securities [Line Items]
Equity securities, Available for sale, Amortized Cost	786	879
Equity securities, Available for sale, Gross Unrealized, Gains	263	160
Equity securities, Available for sale, Gross Unrealized, Losses	(22)	(23)
Equity securities, Available for sale, Net Unrealized, Gains (Losses)	241	137
Equity securities, Available for sale, Fair Value	1,027	1,016
Perpetual preferred stocks
Schedule of Available-for-sale Securities [Line Items]
Equity securities, Available for sale, Amortized Cost	535	472
Equity securities, Available for sale, Gross Unrealized, Gains	39	21
Equity securities, Available for sale, Gross Unrealized, Losses	(1)	(7)
Equity securities, Available for sale, Net Unrealized, Gains (Losses)	38	14
Equity securities, Available for sale, Fair Value	$ 573	$ 486

Investments - Gross unrealized

Investments - Gross unrealized losses on securities by investment category and length of time that have been in a continuous unrealized loss position (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Fixed maturities
Available-for-sale securities in a continuous unrealized loss position
Unrealized Loss - Less than twelve months	$ (37)	$ (196)
Fair Value - Less than twelve months	$ 4,295	$ 8,651
Fair Value as % of Cost - Less than twelve months	99.00%	98.00%
Unrealized Loss - Twelve months or more	$ (45)	$ (49)
Fair Value - Twelve months or more	$ 1,574	$ 1,160
Fair Value as % of Cost - Twelve months or more	97.00%	96.00%
U.S. Government and government agencies
Available-for-sale securities in a continuous unrealized loss position
Unrealized Loss - Less than twelve months	$ 0	$ (1)
Fair Value - Less than twelve months	$ 55	$ 153
Fair Value as % of Cost - Less than twelve months	100.00%	99.00%
Unrealized Loss - Twelve months or more	$ (3)	$ (2)
Fair Value - Twelve months or more	$ 123	$ 8
Fair Value as % of Cost - Twelve months or more	98.00%	80.00%
States, municipalities and political subdivisions
Available-for-sale securities in a continuous unrealized loss position
Unrealized Loss - Less than twelve months	$ (8)	$ (64)
Fair Value - Less than twelve months	$ 825	$ 2,289
Fair Value as % of Cost - Less than twelve months	99.00%	97.00%
Unrealized Loss - Twelve months or more	$ (10)	$ (5)
Fair Value - Twelve months or more	$ 431	$ 44
Fair Value as % of Cost - Twelve months or more	98.00%	90.00%
Foreign government
Available-for-sale securities in a continuous unrealized loss position
Unrealized Loss - Less than twelve months	$ 0
Fair Value - Less than twelve months	$ 4
Fair Value as % of Cost - Less than twelve months	100.00%
Unrealized Loss - Twelve months or more	$ 0
Fair Value - Twelve months or more	$ 0
Fair Value as % of Cost - Twelve months or more	0.00%
Residential MBS
Available-for-sale securities in a continuous unrealized loss position
Unrealized Loss - Less than twelve months	$ (1)	$ (7)
Fair Value - Less than twelve months	$ 118	$ 502
Fair Value as % of Cost - Less than twelve months	99.00%	99.00%
Unrealized Loss - Twelve months or more	$ (5)	$ (6)
Fair Value - Twelve months or more	$ 118	$ 162
Fair Value as % of Cost - Twelve months or more	96.00%	96.00%
Commercial MBS
Available-for-sale securities in a continuous unrealized loss position
Unrealized Loss - Less than twelve months	$ (1)	$ (2)
Fair Value - Less than twelve months	$ 67	$ 121
Fair Value as % of Cost - Less than twelve months	99.00%	98.00%
Unrealized Loss - Twelve months or more	$ 0	$ 0
Fair Value - Twelve months or more	$ 0	$ 0
Fair Value as % of Cost - Twelve months or more	0.00%	0.00%
Asset-backed securities
Available-for-sale securities in a continuous unrealized loss position
Unrealized Loss - Less than twelve months	$ (7)	$ (29)
Fair Value - Less than twelve months	$ 1,195	$ 1,737
Fair Value as % of Cost - Less than twelve months	99.00%	98.00%
Unrealized Loss - Twelve months or more	$ (9)	$ (17)
Fair Value - Twelve months or more	$ 299	$ 634
Fair Value as % of Cost - Twelve months or more	97.00%	97.00%
Corporate and other
Available-for-sale securities in a continuous unrealized loss position
Unrealized Loss - Less than twelve months	$ (20)	$ (93)
Fair Value - Less than twelve months	$ 2,031	$ 3,849
Fair Value as % of Cost - Less than twelve months	99.00%	98.00%
Unrealized Loss - Twelve months or more	$ (18)	$ (19)
Fair Value - Twelve months or more	$ 603	$ 312
Fair Value as % of Cost - Twelve months or more	97.00%	94.00%
Equity securities
Available-for-sale securities in a continuous unrealized loss position
Unrealized Loss - Less than twelve months	$ (22)	$ (29)
Fair Value - Less than twelve months	$ 158	$ 350
Fair Value as % of Cost - Less than twelve months	88.00%	92.00%
Unrealized Loss - Twelve months or more	$ (1)	$ (1)
Fair Value - Twelve months or more	$ 13	$ 6
Fair Value as % of Cost - Twelve months or more	93.00%	86.00%
Common stocks
Available-for-sale securities in a continuous unrealized loss position
Unrealized Loss - Less than twelve months	$ (22)	$ (23)
Fair Value - Less than twelve months	$ 117	$ 215
Fair Value as % of Cost - Less than twelve months	84.00%	90.00%
Unrealized Loss - Twelve months or more	$ 0	$ 0
Fair Value - Twelve months or more	$ 0	$ 0
Fair Value as % of Cost - Twelve months or more	0.00%	0.00%
Perpetual preferred stocks
Available-for-sale securities in a continuous unrealized loss position
Unrealized Loss - Less than twelve months	$ 0	$ (6)
Fair Value - Less than twelve months	$ 41	$ 135
Fair Value as % of Cost - Less than twelve months	100.00%	96.00%
Unrealized Loss - Twelve months or more	$ (1)	$ (1)
Fair Value - Twelve months or more	$ 13	$ 6
Fair Value as % of Cost - Twelve months or more	93.00%	86.00%

Investments - Credit portion of

Investments - Credit portion of other-than-temporary impairments on fixed maturities for which the non-credit portion of an impairment has been recognized in OCI (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Roll Forward]
Balance at January 1	$ 153	$ 160	$ 170
Additional credit impairments on:
Previously impaired securities	1	2	1
Securities without prior impairments	3	1	2
Reductions due to:
Sales or redemptions	(12)	(10)	(9)
Sale of subsidiaries	0	0	(4)
Balance at December 31	$ 145	$ 153	$ 160

Investments - Scheduled maturit

Investments - Scheduled maturities of available for sale fixed maturities (Details) $ in Millions	12 Months Ended
	Dec. 31, 2017USD ($)
Fair Value Percent, Fiscal Year Maturity [Abstract]
Average life of ABS	5 years
Average life of MBS	4 years 6 months
Fixed maturities
Amortized Cost Basis, Fiscal Year Maturity [Abstract]
One year or less	$ 746
After one year through five years	6,730
After five years through ten years	13,235
After ten years	4,680
Fixed maturities amortized cost, Subtotal	25,391
ABS (average life of approximately 5 years)	7,836
MBS (average life of approximately 4.5 years)	3,811
Amortized Cost	37,038
Fair Value, Fiscal Year Maturity [Abstract]
One year or less	759
After one year through five years	6,939
After five years through ten years	13,662
After ten years	4,868
Fixed maturities fair value, Subtotal	26,228
ABS (average life of approximately 5 years)	7,962
MBS (average life of approximately 4.5 years)	4,189
Fair Value	$ 38,379
Fair Value Percent, Fiscal Year Maturity [Abstract]
One year or less	2.00%
After one year through five years	18.00%
After five years through ten years	35.00%
After ten years	13.00%
Fixed maturities fair value, Subtotal, Percent	68.00%
ABS (average life of approximately 5 years)	21.00%
MBS (average life of approximately 4.5 years)	11.00%
Fair value, Total, Percent	100.00%

Investments - Components of the

Investments - Components of the net unrealized gain on securities that is included in AOCI in the Balance Sheet (Details) - USD ($) $ in Millions		Dec. 31, 2017	Dec. 31, 2016
Unrealized gain on:
Pretax		$ 1,063	$ 622
Deferred Tax		(223)	(218)
Net		840	404
Total investments
Unrealized gain on:
Pretax		1,620	960
Deferred Tax		(340)	(336)
Net		1,280	624
Total fixed maturities
Unrealized gain on:
Pretax		1,341	809
Deferred Tax		(282)	(283)
Net		1,059	526
Fixed maturities — annuity segment
Unrealized gain on:
Pretax	[1]	1,082	640
Deferred Tax	[1]	(227)	(224)
Net	[1]	855	416
Fixed maturities — all other
Unrealized gain on:
Pretax		259	169
Deferred Tax		(55)	(59)
Net		204	110
Equity securities
Unrealized gain on:
Pretax	[2]	279	151
Deferred Tax	[2]	(58)	(53)
Net	[2]	221	98
Deferred policy acquisition costs — annuity segment
Unrealized gain on:
Pretax		(433)	(273)
Deferred Tax		91	96
Net		(342)	(177)
Annuity benefits accumulated
Unrealized gain on:
Pretax		(137)	(78)
Deferred Tax		29	27
Net		(108)	(51)
Unearned revenue
Unrealized gain on:
Pretax		13	13
Deferred Tax		(3)	(5)
Net		$ 10	$ 8
[1]	Net unrealized gains on fixed maturity investments supporting AFG’s annuity benefits accumulated.
[2]	As discussed in Note A — “Accounting Policies — Investments,” effective January 1, 2018, all equity securities currently classified as “available for sale” will be required to be carried at fair value through net earnings instead of AOCI.

Investments - Real estate and o

Investments - Real estate and other investments included on the Balance Sheet (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Investment [Line Items]
Limited partnerships and similar investments accounted for using the equity method	$ 999	$ 688
Directly owned real estate	164	197
Other investments	1,311	1,034
Other investments
Investment [Line Items]
Other investments	$ 148	$ 149

Investments - Schedule of sourc

Investments - Schedule of sources of net investment income (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Net Investment Income [Line Items]
Gross investment income	$ 1,852	$ 1,716	$ 1,651
Investment expenses	(21)	(20)	(18)
Net investment income	1,831	1,696	1,633
Fixed maturities
Net Investment Income [Line Items]
Gross investment income	1,607	1,510	1,461
Equity securities
Net Investment Income [Line Items]
Gross investment income	79	81	76
Equity in earnings of partnerships and similar investments
Net Investment Income [Line Items]
Gross investment income	64	44	27
Other
Net Investment Income [Line Items]
Gross investment income	$ 102	$ 81	$ 87

Investments - Realized gains (l

Investments - Realized gains (losses) and changes in unrealized appreciation (depreciation) related to fixed maturity and equity security investments (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Realized gains (losses) and changes in unrealized appreciation (depreciation) related to fixed maturity and equity security investments
Realized before impairments	$ 78	$ 135	$ 106
Realized - impairments	(73)	(116)	(125)
Total realized gains (losses) on securities	5	19	(19)
Net of tax and noncontrolling interests
Realized gains (losses) and changes in unrealized appreciation (depreciation) related to fixed maturity and equity security investments
Realized before impairments	51	85	66
Realized - impairments	(48)	(72)	(78)
Total realized gains (losses) on securities	3	13	(12)
Change in unrealized	436	72	(411)
Total pretax
Realized gains (losses) and changes in unrealized appreciation (depreciation) related to fixed maturity and equity security investments
Realized before impairments	78	135	106
Realized - impairments	(73)	(116)	(125)
Total realized gains (losses) on securities	5	19	(19)
Change in unrealized	441	105	(645)
Fixed maturities
Realized gains (losses) and changes in unrealized appreciation (depreciation) related to fixed maturity and equity security investments
Realized before impairments	17	36	19
Realized - impairments	(20)	(38)	(43)
Total realized gains (losses) on securities	(3)	(2)	(24)
Change in unrealized	532	90	(941)
Equity securities
Realized gains (losses) and changes in unrealized appreciation (depreciation) related to fixed maturity and equity security investments
Realized before impairments	70	106	94
Realized - impairments	(64)	(93)	(94)
Total realized gains (losses) on securities	6	13	0
Change in unrealized	128	67	(134)
Mortgage loans and other investments
Realized gains (losses) and changes in unrealized appreciation (depreciation) related to fixed maturity and equity security investments
Realized before impairments	(6)	0	(2)
Realized - impairments	(4)	0	(3)
Total realized gains (losses) on securities	(10)	0	(5)
Change in unrealized	0	0	0
Other, Including DPAC and reserves on annuities and long-term care
Realized gains (losses) and changes in unrealized appreciation (depreciation) related to fixed maturity and equity security investments
Realized before impairments	(3)	(7)	(5)
Realized - impairments	15	15	15
Total realized gains (losses) on securities	12	8	10
Change in unrealized	(219)	(52)	430
Tax effects
Realized gains (losses) and changes in unrealized appreciation (depreciation) related to fixed maturity and equity security investments
Realized before impairments	(27)	(48)	(38)
Realized - impairments	25	41	45
Total realized gains (losses) on securities	(2)	(7)	7
Change in unrealized	(5)	(37)	226
Noncontrolling interests
Realized gains (losses) and changes in unrealized appreciation (depreciation) related to fixed maturity and equity security investments
Realized before impairments	0	(2)	(2)
Realized - impairments	0	3	2
Total realized gains (losses) on securities	0	1	0
Change in unrealized	$ 0	$ 4	$ 8

Investments - Gross realized ga

Investments - Gross realized gains and losses on available for sale fixed maturity and equity security investment transactions (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Fixed maturities
Gross realized gains and losses on the sale of available for sale fixed maturity and equity security investments
Gross gains	$ 43	$ 55	$ 38
Gross losses	(20)	(10)	(7)
Equity securities
Gross realized gains and losses on the sale of available for sale fixed maturity and equity security investments
Gross gains	87	110	99
Gross losses	$ (17)	$ (4)	$ (5)

Derivatives - Narrative (Detail

Derivatives - Narrative (Details)	1 Months Ended	12 Months Ended
	Dec. 31, 2017USD ($)swap	Dec. 31, 2017USD ($)swap	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)	Dec. 11, 2017	Jun. 30, 2015
Derivative Instruments, Gain (Loss) [Line Items]
Carrying value of collateral received to support purchased call options	$ 389,000,000	$ 389,000,000	$ 380,000,000
Senior Notes | 9-7/8% Senior Notes due June 2019
Derivative Instruments, Gain (Loss) [Line Items]
Stated interest rate, percentage	9.875%	9.875%				9.875%
AFG
Derivative Instruments, Gain (Loss) [Line Items]
Interest rate description of fair value hedge activity		three-month LIBOR plus 8.099%
AFG | Senior Notes | 9-7/8% Senior Notes due June 2019
Derivative Instruments, Gain (Loss) [Line Items]
Stated interest rate, percentage	9.875%	9.875%	9.875%		9.875%	9.875%
Not Designated as Hedging Instrument | Fixed-indexed annuities (embedded derivative) | Annuity benefits
Derivative Instruments, Gain (Loss) [Line Items]
The portion of the change in fair value of the embedded derivative related to the unlocking of actuarial assumptions		$ (25,000,000)	$ (17,000,000)	$ (28,000,000)
Designated as Hedging Instrument | Interest rate swaps | Cash Flow Hedges
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount of derivative instrument outstanding	$ 1,580,000,000	$ 1,580,000,000	1,080,000,000
Designated as Hedging Instrument | Interest rate swaps | Cash Flow Hedges
Derivative Instruments, Gain (Loss) [Line Items]
Number of interest rate swaps designated and qualifying as a cash flow hedges | swap	10	10
Number of interest rate swaps entered into during the period | swap		3
Gain (loss) reclassified from AOCI into net investment income		$ 6,000,000	7,000,000	6,000,000
Gain (loss) on cash flow hedge ineffectiveness recorded in Net Earnings		0	0	0
Collateral receivable supporting interest rate swaps	$ 70,000,000	70,000,000	60,000,000
Designated as Hedging Instrument | Interest rate swaps | Cash Flow Hedges | Other assets
Derivative Instruments, Gain (Loss) [Line Items]
Net derivatives, at fair value			1,000,000
Designated as Hedging Instrument | Interest rate swaps | Cash Flow Hedges | Other assets | Maximum
Derivative Instruments, Gain (Loss) [Line Items]
Net derivatives, at fair value	1,000,000	1,000,000
Designated as Hedging Instrument | Interest rate swaps | Cash Flow Hedges | Other liabilities
Derivative Instruments, Gain (Loss) [Line Items]
Net derivatives, at fair value	(31,000,000)	(31,000,000)	(22,000,000)
Designated as Hedging Instrument | Interest rate swaps | Cash Flow Hedges | New interest rate swaps entered into during the period
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount of derivative instrument outstanding	663,000,000	663,000,000
Designated as Hedging Instrument | Interest rate swaps | Fair Value Hedge | AFG
Derivative Instruments, Gain (Loss) [Line Items]
The net reduction in interest expense from interest rate swaps		$ 2,000,000	3,000,000	$ 2,000,000
Designated as Hedging Instrument | Interest rate swaps | Fair Value Hedge | AFG | Senior Notes | 9-7/8% Senior Notes due June 2019
Derivative Instruments, Gain (Loss) [Line Items]
Settlement of interest rate swap included in the loss on the retirement of debt	$ (1,000,000)
Designated as Hedging Instrument | Interest rate swaps | Fair Value Hedge | AFG | LIBOR
Derivative Instruments, Gain (Loss) [Line Items]
Basis spread on variable interest rate					8.099%
Designated as Hedging Instrument | Interest rate swaps | Fair Value Hedge | Long-term debt | AFG
Derivative Instruments, Gain (Loss) [Line Items]
Net derivatives, at fair value			$ 1,000,000

Derivatives - Derivatives that

Derivatives - Derivatives that do not qualify for hedge accounting under GAAP included in the Balance Sheet at fair value (Details) - Not Designated as Hedging Instrument - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Derivatives included in AFG' s Balance Sheet at fair value
Derivative asset, at fair value	$ 810	$ 603
Derivative liability, at fair value	2,546	1,767
MBS with embedded derivatives | Fixed maturities
Derivatives included in AFG' s Balance Sheet at fair value
Derivative asset, at fair value	105	107
Public company warrants | Equity securities
Derivatives included in AFG' s Balance Sheet at fair value
Derivative asset, at fair value	4	4
Fixed-indexed annuities (embedded derivative) | Annuity benefits accumulated
Derivatives included in AFG' s Balance Sheet at fair value
Derivative liability, at fair value	2,542	1,759
Equity index call options | Equity index call options
Derivatives included in AFG' s Balance Sheet at fair value
Derivative asset, at fair value	701	492
Reinsurance contract (embedded derivative) | Other liabilities
Derivatives included in AFG' s Balance Sheet at fair value
Derivative liability, at fair value	$ 4	$ 8

Derivatives - Gain (loss) inclu

Derivatives - Gain (loss) included in the Statement of Earnings for changes in the fair value of derivatives that do not qualify for hedge accounting (Details) - Not Designated as Hedging Instrument - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Derivative, Gain (Loss) on Derivative, Net [Abstract]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net		$ (103)	$ (80)	$ (83)
MBS with embedded derivatives | Realized gains (losses) on securities
Derivative, Gain (Loss) on Derivative, Net [Abstract]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net		(6)	(9)	(16)
Public company warrants | Realized gains (losses) on securities
Derivative, Gain (Loss) on Derivative, Net [Abstract]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net		0	0	0
Fixed-indexed annuities (embedded derivative) | Annuity benefits
Derivative, Gain (Loss) on Derivative, Net [Abstract]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	[1]	(589)	(211)	(17)
Equity index call options | Annuity benefits
Derivative, Gain (Loss) on Derivative, Net [Abstract]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net		494	141	(56)
Reinsurance contract (embedded derivative) | Net investment income
Derivative, Gain (Loss) on Derivative, Net [Abstract]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net		$ (2)	$ (1)	$ 6
[1]	The change in fair value of the embedded derivative includes losses related to unlocking of actuarial assumptions of $25 million in 2017 compared to $17 million in 2016 and $28 million in 2015.

Deferred Policy Acquisition C69

Deferred Policy Acquisition Costs - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Deferred Policy Acquisition Costs Disclosures [Abstract]
Accumulated amortization of present value of future profits	$ 141	$ 134
Approximate annual rate of decrease in present value of future profits during next five years	12.50%

Deferred Policy Acquisition C70

Deferred Policy Acquisition Costs - Progression of deferred policy acquisition costs (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Movement Analysis of Deferred Policy Acquisition Costs and Present Value of Future Profits [Roll Forward]
Deferred policy acquisition costs and present value of future profits, beginning balance		$ 1,239	$ 1,184	$ 821
Deferred policy acquisition costs and present value of future profits, additions		817	774	754
Deferred policy acquisition costs and present value of future profits, periodic amortization		(744)	(722)	(710)
Deferred policy acquisition costs and present value of future profits, annuity unlocking		41	29	35
Deferred policy acquisition costs and present value of future profits, change included in realized gains		10	8	9
Deferred policy acquisition costs and present value of future profits, sale of subsidiaries				(19)
Deferred policy acquisition costs and present value of future profits, foreign currency translation		0	(3)	(3)
Deferred policy acquisition costs and present value of future profits, other		10
Deferred policy acquisition costs and present value of future profits, change in unrealized		(157)	(31)	297
Deferred policy acquisition costs and present value of future profits, ending balance		1,216	1,239	1,184
Property and casualty insurance
Movement Analysis of Deferred Policy Acquisition Costs [Roll Forward]
Deferred policy acquisition costs, beginning balance		238	226	221
Deferred policy acquisition costs, additions		588	535	519
Deferred policy acquisition costs, periodic amortization		(556)	(520)	(511)
Deferred policy acquisition costs, foreign currency translation		0	(3)	(3)
Deferred policy acquisition costs, ending balance		270	238	226
Annuity and Run-off Long-term Care and Life
Movement Analysis of Deferred Policy Acquisition Costs [Roll Forward]
Deferred policy acquisition costs, beginning balance		1,110	1,018	925
Deferred policy acquisition costs, additions		225	230	224
Deferred policy acquisition costs, periodic amortization		(161)	(169)	(162)
Deferred policy acquisition costs, annuity unlocking		34	25	31
Deferred policy acquisition costs, change included in realized gains		9	6	8
Deferred policy acquisition costs, sale of subsidiaries				(8)
Deferred policy acquisition costs, ending balance		1,217	1,110	1,018
Movement in Deferred Sales Inducements [Roll Forward]
Deferred sales inducements, beginning balance		110	119	132
Deferred sales inducements, additions		4	9	11
Deferred sales inducements, periodic amortization		(19)	(24)	(26)
Deferred sales inducements, annuity unlocking		6	4	4
Deferred sales inducements, change included in realized gains		1	2	1
Deferred sales inducements, sale of subsidiaries				(3)
Deferred sales inducements, ending balance		102	110	119
Movement in Present Value of Future Insurance Profits [Roll Forward]
Present value of future profits, beginning balance		46	55	74
Present value of future profits, periodic amortization		(8)	(9)	(11)
Present value of future profits, annuity unlocking		1	0	0
Present value of future profits, sale of subsidiaries				(8)
Present value of future profits, other		10
Present value of future profits, ending balance		49	46	55
Movement in Unrealized Gains (Losses) Related to Deferred Policy Acquisition Costs and Present Value of Future Profits [Roll Forward]
Unrealized investment gains (losses), beginning balance	[1]	(265)	(234)	(531)
Unrealized investment gains (losses), change in unrealized	[1]	(157)	(31)	297
Unrealized investment gains (losses), ending balance	[1]	(422)	(265)	(234)
Movement Analysis of Deferred Policy Acquisition Costs and Present Value of Future Profits [Roll Forward]
Deferred policy acquisition costs and present value of future profits, beginning balance		1,001	958	600
Deferred policy acquisition costs and present value of future profits, additions		229	239	235
Deferred policy acquisition costs and present value of future profits, periodic amortization		(188)	(202)	(199)
Deferred policy acquisition costs and present value of future profits, annuity unlocking		41	29	35
Deferred policy acquisition costs and present value of future profits, change included in realized gains		10	8	9
Deferred policy acquisition costs and present value of future profits, sale of subsidiaries				(19)
Deferred policy acquisition costs and present value of future profits, other		10
Deferred policy acquisition costs and present value of future profits, change in unrealized		(157)	(31)	297
Deferred policy acquisition costs and present value of future profits, ending balance		946	1,001	958
Excluding Unrealized Gains | Annuity and Run-off Long-term Care and Life
Movement Analysis of Deferred Policy Acquisition Costs and Present Value of Future Profits [Roll Forward]
Deferred policy acquisition costs and present value of future profits, beginning balance		1,266	1,192	1,131
Deferred policy acquisition costs and present value of future profits, change in unrealized		0	0	0
Deferred policy acquisition costs and present value of future profits, ending balance		$ 1,368	$ 1,266	$ 1,192
[1]	Unrealized adjustments to DPAC includes net unrealized gains/losses on securities and net unrealized gains/losses on cash flow hedges.

Managed Investment Entities - N

Managed Investment Entities - Narrative (Details) $ in Millions	12 Months Ended
	Dec. 31, 2017USD ($)collateralizedloanobligation	Dec. 31, 2016USD ($)collateralizedloanobligation	Dec. 31, 2015USD ($)collateralizedloanobligation
Variable Interest Entity [Line Items]
Percentage of investment of most subordinate debt tranche, Minimum	15.00%
Percentage of investment of most subordinate debt tranche, Maximum	60.90%
Number of collateralized loan obligation entities | collateralizedloanobligation	15
Number of collateralized loan obligation entities formed during the period | collateralizedloanobligation	2	2	2
Face amount of managed investment entities liabilities purchased by subsidiaries after issuance date	$ 71	$ 24
Amount paid by subsidiaries to purchase managed investment entities liabilities after issuance date	71	17
Proceeds received by subsidiaries related to sales and redemptions of managed investment entities liabilities	$ 103	115
Number of collateralized loan obligation entities that were substantially liquidated during the period | collateralizedloanobligation	2
Difference between aggregate unpaid principal balance and fair value of CLOs' fixed maturity investments	$ 55	75
Difference between aggregate unpaid principal balance and fair value of CLOs' debt	118	159
Carrying amount of CLO loans in default	1	1
Aggregate unpaid principal balance of CLO loans in default	8	10
Variable interest entity, primary beneficiary
Variable Interest Entity [Line Items]
Aggregate fair value of investment in collateralized loan obligations	215	216	$ 266
New collateralized loan obligation entities
Variable Interest Entity [Line Items]
Face value of liabilities issued by managed investment entities on issuance date	865	866	869
Face amount of managed investment entities liabilities purchased by subsidiaries at issuance date	48	$ 64	$ 81
Subordinated debt obligations | Variable interest entity, primary beneficiary
Variable Interest Entity [Line Items]
Aggregate fair value of investment in collateralized loan obligations	$ 130

Managed Investment Entities - S

Managed Investment Entities - Selected financial information related to CLOs (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Gains (losses) on change in fair value of assets/liabilities:
Assets	[1]	$ (8)	$ 131	$ (116)
Liabilities	[1]	20	(116)	82
Management fees paid to AFG		18	17	15
CLO earnings (losses) attributable to AFG Shareholders	[2]	23	37	(6)
Variable interest entity, primary beneficiary
Variable Interest Entity [Line Items]
Investment in CLO tranches		$ 215	$ 216	$ 266
[1]	Included in revenues in AFG’s Statement of Earnings.
[2]	Included in earnings before income taxes in AFG’s Statement of Earnings.

Goodwill and Other Intangible73

Goodwill and Other Intangibles - Narrative (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill decrease due to the sale of a subsidiary	$ (2)			$ (2)
Amortizable intangible assets related to property and casualty insurance acquisitions		$ 26	$ 34
Accumulated amortization		30	25
Amortization of intangible assets		$ 8	$ 8	$ 8
Weighted average useful life of finite-lived intangible assets acquired		3 years
Future amortization of intangibles in next year		$ 8
Future amortization of intangibles in year two		8
Future amortization of intangibles in year three		8
Future amortization of intangibles in year four		$ 2

Goodwill and Other Intangible74

Goodwill and Other Intangibles - Changes in the carrying value of goodwill (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2014
Changes in the carrying value of goodwill by reporting segment
Goodwill, Beginning balance	$ 199	$ 199	$ 199	$ 199	$ 201
Goodwill, Sale of subsidiary	(2)	(2)
Goodwill, Ending balance	199	199
Property and Casualty
Changes in the carrying value of goodwill by reporting segment
Goodwill, Beginning balance	168	168	168	168	168
Goodwill, Sale of subsidiary		0
Goodwill, Ending balance	168	168
Annuity
Changes in the carrying value of goodwill by reporting segment
Goodwill, Beginning balance	31	31	$ 31	$ 31	$ 33
Goodwill, Sale of subsidiary		(2)
Goodwill, Ending balance	$ 31	$ 31

Long-Term Debt - Narrative (Det

Long-Term Debt - Narrative (Details) - USD ($)	1 Months Ended	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 11, 2017	Nov. 30, 2017	Aug. 31, 2017	Jun. 30, 2017	Nov. 10, 2016	Aug. 31, 2016	Nov. 30, 2015	Sep. 30, 2015	Jun. 30, 2015
Long-term Debt, Fiscal Year Maturity [Abstract]
Scheduled principal payments on debt in next year	$ 0	$ 0
Scheduled principal payments on debt in year two	0	0
Scheduled principal payments on debt in year three	0	0
Scheduled principal payments on debt in year four	0	0
Scheduled principal payments on debt in year five	0	0
Scheduled principal payments on debt after year five	1,320,000,000	1,320,000,000
Principal	1,318,000,000	1,318,000,000	$ 1,308,000,000
Cash interest payments on long-term debt		85,000,000	75,000,000	$ 75,000,000
AFG
Long-term Debt, Fiscal Year Maturity [Abstract]
Revolving credit line	500,000,000	500,000,000
Amount borrowed under AFG revolving credit facility	0	$ 0	0
Interest rate description of fair value hedge activity		three-month LIBOR plus 8.099%
Interest rate description for revolving credit facility		1.00% to 1.875% (currently 1.375%) over LIBOR
LIBOR | AFG
Long-term Debt, Fiscal Year Maturity [Abstract]
Interest rate on revolving debt facility		1.375%
LIBOR | AFG | Minimum
Long-term Debt, Fiscal Year Maturity [Abstract]
Interest rate on revolving debt facility		1.00%
LIBOR | AFG | Maximum
Long-term Debt, Fiscal Year Maturity [Abstract]
Interest rate on revolving debt facility		1.875%
Interest rate swaps | Fair Value Hedge | Designated as Hedging Instrument | AFG
Long-term Debt, Fiscal Year Maturity [Abstract]
Cash interest received on long-term debt affiliated with interest rate swap		$ 2,000,000	3,000,000	$ 2,000,000
Interest rate swaps | Fair Value Hedge | Designated as Hedging Instrument | LIBOR | AFG
Long-term Debt, Fiscal Year Maturity [Abstract]
Basis spread on variable interest rate					8.099%
Long-term debt | Interest rate swaps | Fair Value Hedge | Designated as Hedging Instrument | AFG
Long-term Debt, Fiscal Year Maturity [Abstract]
Net derivatives, at fair value			1,000,000
Senior Notes | AFG
Long-term Debt, Fiscal Year Maturity [Abstract]
Principal	1,018,000,000	1,018,000,000	1,008,000,000
Senior Notes | 4.50% Senior Notes due June 2047 | AFG
Long-term Debt, Fiscal Year Maturity [Abstract]
Senior Notes, aggregate principal amount						$ 240,000,000		$ 350,000,000
Senior Notes, issuance price as a percentage of par value						102.374%		99.46%
Principal	$ 590,000,000	$ 590,000,000	0
Interest rate on debt instruments	4.50%	4.50%				4.50%		4.50%
Senior Notes | 3.50% Senior Notes due August 2026 | AFG
Long-term Debt, Fiscal Year Maturity [Abstract]
Senior Notes, aggregate principal amount						$ 125,000,000				$ 300,000,000
Senior Notes, issuance price as a percentage of par value						99.698%				99.608%
Principal	$ 425,000,000	$ 425,000,000	300,000,000
Interest rate on debt instruments	3.50%	3.50%				3.50%				3.50%
Senior Notes | 9-7/8% Senior Notes due June 2019
Long-term Debt, Fiscal Year Maturity [Abstract]
Interest rate on debt instruments	9.875%	9.875%											9.875%
Senior Notes | 9-7/8% Senior Notes due June 2019 | AFG
Long-term Debt, Fiscal Year Maturity [Abstract]
Senior Notes, amount of the original debt instrument that was redeemed					$ 350,000,000
Senior Notes, amount of the original debt instrument that was redeemed plus a make-whole premium					$ 388,000,000
Principal	$ 0	$ 0	$ 350,000,000
Interest rate on debt instruments	9.875%	9.875%	9.875%		9.875%								9.875%
Senior Notes | 9-7/8% Senior Notes due June 2019 | Interest rate swaps | Fair Value Hedge | Designated as Hedging Instrument | AFG
Long-term Debt, Fiscal Year Maturity [Abstract]
Make-whole premium included in the loss on the retirement of debt	$ (1,000,000)
Senior Notes | 6-3/8% Senior Notes due June 2042 | AFG
Long-term Debt, Fiscal Year Maturity [Abstract]
Senior Notes, amount of the original debt instrument that was redeemed								$ 230,000,000
Principal	$ 0	$ 0	$ 230,000,000
Interest rate on debt instruments	6.375%	6.375%						6.375%
Senior Notes | 5-3/4% Senior Notes due August 2042 | AFG
Long-term Debt, Fiscal Year Maturity [Abstract]
Senior Notes, amount of the original debt instrument that was redeemed							$ 125,000,000
Principal	$ 0	$ 0	125,000,000
Interest rate on debt instruments	5.75%	5.75%					5.75%
Senior Notes | 7% Senior Notes due September 2050
Long-term Debt, Fiscal Year Maturity [Abstract]
Senior Notes, amount of the original debt instrument that was redeemed												$ 132,000,000
Senior Notes | 7% Senior Notes due September 2050 | AFG
Long-term Debt, Fiscal Year Maturity [Abstract]
Interest rate on debt instruments												7.00%
Subordinated Debt | AFG
Long-term Debt, Fiscal Year Maturity [Abstract]
Principal	$ 300,000,000	$ 300,000,000	300,000,000
Subordinated Debt | 6-1/4% Subordinated Debentures due September 2054 | AFG
Long-term Debt, Fiscal Year Maturity [Abstract]
Principal	$ 150,000,000	$ 150,000,000	150,000,000
Interest rate on debt instruments	6.25%	6.25%
Subordinated Debt | 6% Subordinated Debentures due November 2055 | AFG
Long-term Debt, Fiscal Year Maturity [Abstract]
Senior Notes, aggregate principal amount											$ 150,000,000
Principal	$ 150,000,000	$ 150,000,000	$ 150,000,000
Interest rate on debt instruments	6.00%	6.00%									6.00%
Revolving Credit Facility | National Interstate
Long-term Debt, Fiscal Year Maturity [Abstract]
Principal									$ 18,000,000
Revolving Credit Facility | Line of Credit | National Interstate
Long-term Debt, Fiscal Year Maturity [Abstract]
Principal									$ 6,000,000
Make-whole premium | Senior Notes | 9-7/8% Senior Notes due June 2019 | AFG
Long-term Debt, Fiscal Year Maturity [Abstract]
Make-whole premium included in the loss on the retirement of debt	$ (38,000,000)

Long-Term Debt - Schedule of lo

Long-Term Debt - Schedule of long-term debt (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Summary of Carrying value of long-term debt
Principal	$ 1,318	$ 1,308
Discount and Issue Costs	(17)	(25)
Carrying Value	1,301	1,283
AFG
Summary of Carrying value of long-term debt
Carrying Value	1,301	1,283
Senior Notes | AFG
Summary of Carrying value of long-term debt
Principal	1,018	1,008
Discount and Issue Costs	(7)	(15)
Carrying Value	1,011	993
Senior Notes | 4.50% Senior Notes due June 2047 | AFG
Summary of Carrying value of long-term debt
Principal	590	0
Discount and Issue Costs	(2)	0
Carrying Value	588	0
Senior Notes | 3.50% Senior Notes due August 2026 | AFG
Summary of Carrying value of long-term debt
Principal	425	300
Discount and Issue Costs	(5)	(3)
Carrying Value	420	297
Senior Notes | 9-7/8% Senior Notes due June 2019 | AFG
Summary of Carrying value of long-term debt
Principal	0	350
Discount and Issue Costs	0	(1)
Carrying Value	0	349
Senior Notes | 6-3/8% Senior Notes due June 2042 | AFG
Summary of Carrying value of long-term debt
Principal	0	230
Discount and Issue Costs	0	(7)
Carrying Value	0	223
Senior Notes | 5-3/4% Senior Notes due August 2042 | AFG
Summary of Carrying value of long-term debt
Principal	0	125
Discount and Issue Costs	0	(4)
Carrying Value	0	121
Senior Notes | Other | AFG
Summary of Carrying value of long-term debt
Principal	3	3
Discount and Issue Costs	0	0
Carrying Value	3	3
Subordinated Debentures | AFG
Summary of Carrying value of long-term debt
Principal	300	300
Discount and Issue Costs	(10)	(10)
Carrying Value	290	290
Subordinated Debentures | 6-1/4% Subordinated Debentures due September 2054 | AFG
Summary of Carrying value of long-term debt
Principal	150	150
Discount and Issue Costs	(5)	(5)
Carrying Value	145	145
Subordinated Debentures | 6% Subordinated Debentures due November 2055 | AFG
Summary of Carrying value of long-term debt
Principal	150	150
Discount and Issue Costs	(5)	(5)
Carrying Value	$ 145	$ 145

Shareholders' Equity - Narrativ

Shareholders' Equity - Narrative (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Rate of options exercisable per year, commencing one year after grant			20% per year commencing one year after grant
Duration of options expiration, after date of grant			10 years
Total intrinsic value of options exercised			$ 65	$ 38	$ 52
Cash received from the exercise of stock options			33	32	47
Tax benefit related to exercise of stock options			18	11	16
Total compensation expense related to stock incentive plans			30	28	27
Tax benefit related to compensation costs			27	19	8
Net of tax unrealized gains (losses) related to credit-only impaired securities			68	$ 52	51
Impact of the U.S. corporate tax rate change on AOCI			$ 0			$ 2
Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted Common Stock vesting period			3 years
Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted Common Stock vesting period			4 years
Stock Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common Stock reserved for issuance under stock incentive plans (shares)			8,000,000
Common Stock options issued under stock incentive plan (shares)			0	0
Annual Equity Bonus Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Other benefit plans, shares issued (shares)	47,826	40,336
Common Stock issued, fair value per share (USD per share)	$ 96.13	$ 71.05
Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation expense related to equity-based awards that have yet to vest			$ 7
Weighted average period of cost expected to be recognized			1 year 8 months 12 days
Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation expense related to equity-based awards that have yet to vest			$ 31
Weighted average period of cost expected to be recognized			2 years 7 months 6 days
Capital surplus
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Tax benefit related to exercise of stock options					$ 12
Capital surplus under previous accounting guidance | Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Tax benefit related to exercise of stock options			$ 17	$ 9
Accounting Standards Update 2018-02 | Tax Cuts and Jobs Act of 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Impact of the U.S. corporate tax rate change on AOCI			$ 145

Shareholders' Equity - Preferre

Shareholders' Equity - Preferred stock authorized for issuance (Details)	Dec. 31, 2017$ / sharesshares
Voting Preferred Stock
Class of Stock [Line Items]
Preferred Stock, par value | $ / shares	$ 0
Preferred Stock, shares authorized | shares	12,500,000
Nonvoting Preferred Stock
Class of Stock [Line Items]
Preferred Stock, par value | $ / shares	$ 0
Preferred Stock, shares authorized | shares	12,500,000

Shareholders' Equity - Data rel

Shareholders' Equity - Data relating to grants of restricted stock (Details) - Restricted Stock	12 Months Ended
	Dec. 31, 2017$ / sharesshares
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Outstanding at January 1, 2017 | shares	678,875
Granted | shares	232,250
Vested | shares	(145,473)
Forfeited | shares	(6,617)
Outstanding at December 31, 2017 | shares	759,035
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Roll Forward]
Average grant date fair value, Outstanding, Beginning balance | $ / shares	$ 60.90
Average grant date fair value, Granted | $ / shares	94.44
Average grant date fair value, Vested | $ / shares	48.76
Average grant date fair value, Forfeited | $ / shares	71.30
Average grant date fair value, Outstanding, Ending balance | $ / shares	$ 73.40

Shareholders' Equity - Data for

Shareholders' Equity - Data for stock options issued under the stock incentive plans (Details) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2017USD ($)$ / sharesshares
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Outstanding at January 1, 2017 | shares	4,505,101
Exercised | shares	(1,020,986)
Forfeited/Cancelled | shares	(16,775)
Outstanding at December 31, 2017 | shares	3,467,340
Options exercisable at December 31, 2017 | shares	2,589,277
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Roll Forward]
Average exercise price, Beginning balance | $ / shares	$ 43.02
Average exercise price, Exercised | $ / shares	33.38
Average exercise price, Forfeited/Cancelled | $ / shares	55.82
Average exercise price, Ending balance | $ / shares	45.80
Average exercise price, Options exercisable | $ / shares	$ 42
Average remaining contractual term, Options outstanding	4 years 10 months 24 days
Average remaining contractual term, Options exercisable	4 years 4 months 24 days
Aggregate intrinsic value, Options outstanding | $	$ 218
Aggregate intrinsic value, Options exercisable | $	$ 172

Shareholders' Equity - Assumpti

Shareholders' Equity - Assumptions used in estimating weighted average fair value of options on grant date (Details)	12 Months Ended
	Dec. 31, 2015$ / shares
Stock Options, Valuation Assumptions
Exercise price	$ 63.15
Expected dividend yield	1.60%
Expected volatility	25.00%
Expected term (in years)	7 years 3 months
Risk-free rate	1.88%
Grant date fair value	$ 15.29

Shareholders' Equity - Progress

Shareholders' Equity - Progression of the components of accumulated other comprehensive income (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2017		Dec. 31, 2016		Dec. 31, 2015
Accumulated Other Comprehensive Income [Roll Forward]
AOCI beginning balance		$ 375
Other comprehensive income (loss), net of tax		296		$ 67		$ (431)
Other comprehensive income (loss), net of tax, acquisition of noncontrolling interest				(315)
AOCI ending balance		813		375
Accumulated net investment gain (loss) including portion attributable to noncontrolling interest
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss), unrealized holding gains on securities arising during the period, Pretax		456		124		(625)
Other comprehensive income (loss), unrealized holding gains on securities arising during the period, tax		(159)		(44)		219
Other comprehensive income (loss), unrealized holding gains on securities arising during the period, net of tax		297		80		(406)
Reclassification from accumulated other comprehensive income, pretax	[1]	(15)		(19)		14
Reclassification from accumulated other comprehensive income, tax	[1]	5		7		(5)
Reclassification from accumulated other comprehensive income, net of tax		(10)		(12)		9
Accumulated Other Comprehensive Income [Roll Forward]
Other comprehensive income (loss), pretax		441		105		(645)
Other comprehensive income (loss), tax		(154)		(37)		226
Other comprehensive income (loss), net of tax		287		68		(419)
Accumulated net investment gain (loss) including portion attributable to noncontrolling interest | Reclassification out of Accumulated Other Comprehensive Income
Accumulated Other Comprehensive Income (Loss) [Line Items]
Reclassification from accumulated other comprehensive income, pretax						(34)
Reclassification from accumulated other comprehensive income, tax						12
Reclassification from accumulated other comprehensive income, net of tax						(22)
Accumulated net investment gain (loss) attributable to noncontrolling interest
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss), unrealized holding gains on securities arising during the period, net of tax		0		(4)		9
Reclassification from accumulated other comprehensive income, net of tax	[1]	0		(1)		(1)
Accumulated Other Comprehensive Income [Roll Forward]
Other comprehensive income (loss), net of tax		0		(5)		8
Accumulated net investment gain (loss) attributable to noncontrolling interest | Reclassification out of Accumulated Other Comprehensive Income
Accumulated Other Comprehensive Income (Loss) [Line Items]
Reclassification from accumulated other comprehensive income, net of tax						0
Accumulated net investment gain (loss) attributable to parent
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss), unrealized holding gains on securities arising during the period, net of tax		297		76		(397)
Reclassification from accumulated other comprehensive income, net of tax		(10)		(13)		8
Accumulated Other Comprehensive Income [Roll Forward]
AOCI beginning balance		404	[2]	332	[2]	743
Other comprehensive income (loss), net of tax		287		63		(411)
AOCI, Other, including the impact of the Tax Cuts and Jobs Act of 2017 and the sale of redeemable noncontrolling interests in subsidiaries	[3]	149
Other comprehensive income (loss), net of tax, acquisition of noncontrolling interest	[3]			9
AOCI ending balance	[2]	840		404		332
Accumulated net investment gain (loss) attributable to parent | Reclassification out of Accumulated Other Comprehensive Income
Accumulated Other Comprehensive Income (Loss) [Line Items]
Reclassification from accumulated other comprehensive income, net of tax						(22)
Accumulated net gain (loss) from cash flow hedges including portion attributable to noncontrolling interest
Accumulated Other Comprehensive Income [Roll Forward]
Other comprehensive income (loss), pretax		(6)		(12)		1
Other comprehensive income (loss), tax		2		4		0
Other comprehensive income (loss), net of tax		(4)		(8)		1
Accumulated net gain (loss) from cash flow hedges attributable to noncontrolling interest
Accumulated Other Comprehensive Income [Roll Forward]
Other comprehensive income (loss), net of tax		0		0		0
Accumulated net gain (loss) from cash flow hedges attributable to parent
Accumulated Other Comprehensive Income [Roll Forward]
AOCI beginning balance		(7)		1		0
Other comprehensive income (loss), net of tax		(4)		(8)		1
AOCI, Other, including the impact of the Tax Cuts and Jobs Act of 2017 and the sale of redeemable noncontrolling interests in subsidiaries	[3]	(2)
AOCI ending balance		(13)		(7)		1
Accumulated foreign currency adjustment including portion attributable to noncontrolling interest
Accumulated Other Comprehensive Income [Roll Forward]
Other comprehensive income (loss), pretax		9		6		(9)
Other comprehensive income (loss), tax		3		1		(5)
Other comprehensive income (loss), net of tax		12		7		(14)
Accumulated foreign currency adjustment attributable to noncontrolling interest
Accumulated Other Comprehensive Income [Roll Forward]
Other comprehensive income (loss), net of tax		0		0		0
Accumulated foreign currency adjustment attributable to parent
Accumulated Other Comprehensive Income [Roll Forward]
AOCI beginning balance		(15)		(22)		(8)
Other comprehensive income (loss), net of tax		12		7		(14)
AOCI, Other, including the impact of the Tax Cuts and Jobs Act of 2017 and the sale of redeemable noncontrolling interests in subsidiaries	[3]	(3)
AOCI ending balance		(6)		(15)		(22)
Accumulated defined benefit plans adjustment including portion attributable to noncontrolling interest
Accumulated Other Comprehensive Income [Roll Forward]
Other comprehensive income (loss), pretax		1		0		1
Other comprehensive income (loss), tax		0		0		0
Other comprehensive income (loss), net of tax		1		0		1
Accumulated defined benefit plans adjustment attributable to noncontrolling interest
Accumulated Other Comprehensive Income [Roll Forward]
Other comprehensive income (loss), net of tax		0		0		0
Accumulated defined benefit plans adjustment attributable to parent
Accumulated Other Comprehensive Income [Roll Forward]
AOCI beginning balance		(7)		(7)		(8)
Other comprehensive income (loss), net of tax		1		0		1
AOCI, Other, including the impact of the Tax Cuts and Jobs Act of 2017 and the sale of redeemable noncontrolling interests in subsidiaries	[3]	(2)
AOCI ending balance		(8)		(7)		(7)
AOCI including portion attributable to noncontrolling interest
Accumulated Other Comprehensive Income [Roll Forward]
Other comprehensive income (loss), pretax		445		99		(652)
Other comprehensive income (loss), tax		(149)		(32)		221
Other comprehensive income (loss), net of tax		296		67		(431)
AOCI attributable to noncontrolling interest
Accumulated Other Comprehensive Income [Roll Forward]
Other comprehensive income (loss), net of tax		0		(5)		8
AOCI attributable to parent
Accumulated Other Comprehensive Income [Roll Forward]
AOCI beginning balance		375		304		727
Other comprehensive income (loss), net of tax		296		62		(423)
AOCI, Other, including the impact of the Tax Cuts and Jobs Act of 2017 and the sale of redeemable noncontrolling interests in subsidiaries	[3]	142
Other comprehensive income (loss), net of tax, acquisition of noncontrolling interest	[3]			9
AOCI ending balance		$ 813		$ 375		$ 304
[1]	The reclassification adjustment out of net unrealized gains on securities affected the following lines in AFG’s Statement of Earnings: OCI component Affected line in the statement of earnings Pretax Realized gains (losses) on securities Tax Provision for income taxes Attributable to noncontrolling interests Net earnings attributable to noncontrolling interests
[2]	Includes net unrealized gains of $68 million at December 31, 2017 compared to net unrealized gains of $52 million and $51 million at December 31, 2016 and 2015, related to securities for which only the credit portion of an other-than-temporary impairment has been recorded in earnings.
[3]	Other includes the December 2017 reclassification of $145 million stranded in AOCI from accounting for the Tax Cuts and Jobs Act of 2017 to retained earnings (see Note A — “Accounting Policies — Income Taxes”), and the impact on AOCI of the December 2017 sale of redeemable noncontrolling interests in Neon and the November 2016 acquisition of the noncontrolling interest in NATL (see Note B — “Acquisitions and Sale of Businesses”).

Income Taxes - Narrative (Detai

Income Taxes - Narrative (Details) £ in Millions, $ in Millions		Jan. 01, 2018	Jan. 31, 2008USD ($)	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)	Jun. 30, 2016USD ($)	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)	Dec. 31, 2012USD ($)	Dec. 31, 2017GBP (£)
Income Tax Reconciliation [Line Items]
Statutory rate of income taxes							35.00%	35.00%	35.00%
Payments to acquire additional interest in subsidiaries							$ 0	$ 315	$ 0
impact of foreign operations included in the provision for income taxes							21	5	3
Decrease in the valuation allowance related to the change in the U.S. corporate tax rate							(7)	52	23
Income tax expense (benefit)							247	119	195
Decrease in net deferred tax assets resulting from the changes in the Tax Cuts and Jobs Act of 2017							$ 83	$ 0	0
Effective tax rate excluding the charge related to the exit of certain lines of business within subsidiaries and impact of the change in the U.S. corporate tax rate							31.00%
Effective tax rate excluding the charge related to the exit of certain lines of business within subsidiaries, acquisition of the noncontrolling interest, and restructuring of subsidiaries								35.00%
Income (losses) subject to tax in foreign jurisdictions							$ (58)	$ (160)	(66)
Operating loss carryforwards, valuation allowance				$ 27			27
Decrease in AFG's liability for uncertain tax positions, settlements							(1)	0	0
Change in AFG's liability for uncertain tax positions of prior year							0	0	0
Cash payments for income taxes							$ 194	308	234
Limitation on the use of tax credit carryforwards							A SRLY NOL can be used only by the entity that created it and only in years that both it and the consolidated group have taxable income. Approximately $13 million of AFG’s SRLY NOLs expired unutilized at December 31, 2017.
AFG
Income Tax Reconciliation [Line Items]
Income tax expense (benefit)				(56)	$ (177)		$ 247	119	195
Amount of expense for penalties related to a tax position									0
National Interstate
Income Tax Reconciliation [Line Items]
Income tax expense (benefit)					(66)
Neon Capital Limited
Income Tax Reconciliation [Line Items]
Income tax expense (benefit)				(56)	(111)			(48)
Increase (Decrease) in current taxes payable				(20)	(29)
Charge for valuation allowance
Income Tax Reconciliation [Line Items]
Charge for valuation allowance against deferred tax assets							80
Maximum | AFG
Income Tax Reconciliation [Line Items]
Unrecognized tax benefits that would impact the effective tax rate				1	1		1	1
Interest included in tax provision							(1)	1	1
Decrease in related accrued interest (are less than in 2017 and 2016)				1	1		1	1
Amount of expense for penalties related to a tax position							1	1
Income tax penalties accrued				1	$ 1		1	1
Amount Unutilized [Member]
Income Tax Reconciliation [Line Items]
Operating loss carryforwards				13			13
Tax Cuts and Jobs Act of 2017
Income Tax Reconciliation [Line Items]
Decrease in net deferred tax assets resulting from the changes in the Tax Cuts and Jobs Act of 2017							83
Tax Cuts and Jobs Act of 2017 | Neon Capital Limited
Income Tax Reconciliation [Line Items]
Decrease in the valuation allowance related to the change in the U.S. corporate tax rate							(61)
United Kingdom
Income Tax Reconciliation [Line Items]
Operating loss carryforwards	[1]			$ 252			252				£ 186
Property and casualty insurance
Income Tax Reconciliation [Line Items]
Change in AFG’s liability for uncertain tax positions due to the uncertainty in state taxation									$ 1
Tax payments due to resolved uncertainty in state taxation							1
Property and casualty insurance | Other lines
Income Tax Reconciliation [Line Items]
Special charges related to the exit of certain lines of business within subsidiaries						$ 65		65
Property and casualty insurance | Other lines | Neon Capital Limited
Income Tax Reconciliation [Line Items]
Special charges related to the exit of certain lines of business within subsidiaries								$ 65
Neon Capital Limited
Income Tax Reconciliation [Line Items]
Payments to acquire controlling interest in subsidiaries			$ 75
Percentage ownership of subsidiary			67.00%
Payments to acquire additional interest in subsidiaries										$ 17
Subsequent Event | Tax Cuts and Jobs Act of 2017
Income Tax Reconciliation [Line Items]
Statutory rate of income taxes		21.00%
Foreign underwriting losses
Income Tax Reconciliation [Line Items]
impact of foreign operations included in the provision for income taxes							$ 14
[1]	£186 million

Income Taxes - Reconciliation o

Income Taxes - Reconciliation of income taxes at the statutory rate to the provision for income taxes (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Effective Income Tax Rate Reconciliation, Amount [Abstract]
Earnings before income taxes (“EBT”)	$ 724	$ 787	$ 565
Income taxes at statutory rate	253	275	198
Effect of tax exempt interest	(23)	(24)	(27)
Effect of dividends received deduction	(8)	(7)	(8)
Effect of stock-based compensation	(16)	(9)	1
Effect of employee stock ownership plan dividend paid deduction	(5)	(2)	(1)
Effect of foreign operations	21	5	3
Effect of change in valuation allowance (excluding change in tax rate)	(7)	52	23
Effect of subsidiaries not in AFG's tax return	0	3	2
Effect of Neon restructuring	(56)	(111)	0
Effect of change in U.S corporate tax rate	83	0	0
Effect of acquisition of noncontrolling interest	0	(66)	0
Effect of other income tax reconciliation	5	3	4
Provision for income taxes as shown in the Statement of Earnings	$ 247	$ 119	$ 195
Effective Income Tax Rate Reconciliation, Percent [Abstract]
Income taxes at statutory rate as a percentage of EBT	35.00%	35.00%	35.00%
Effect of tax exempt interest as a percentage of EBT	(3.00%)	(3.00%)	(5.00%)
Effect of dividend received deduction as a percentage of EBT	(1.00%)	(1.00%)	(1.00%)
Effect of stock-based compensation as a percentage of EBT	(2.00%)	(1.00%)	0.00%
Effect of employee stock ownership plan dividend paid deduction as a percentage of EBT	(1.00%)	(0.00%)	(0.00%)
Effect of foreign operations as a percentage of EBT	3.00%	0.00%	1.00%
Effect of change in valuation allowance (excluding change in tax rate) as a percentage of EBT	(1.00%)	7.00%	4.00%
Effect of subsidiaries not in AFG's tax return as a percentage of EBT	0.00%	0.00%	0.00%
Effect of Neon restructuring as a percentage of EBT	(8.00%)	(14.00%)	0.00%
Effect of change in U.S corporate tax rate as a percentage of EBT	11.00%	0.00%	0.00%
Effect of acquisition of noncontrolling interest as a percentage of EBT	0.00%	(8.00%)	0.00%
Effect of other income tax reconciliation as a percentage of EBT	1.00%	0.00%	1.00%
Provision for income taxes as shown in the Statement of Earnings as a percentage of EBT	34.00%	15.00%	35.00%

Income Taxes - Total income tax

Income Taxes - Total income tax provision (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Current taxes:
Federal	$ 153	$ 299	$ 216
State	6	12	8
Deferred taxes:
Federal	5	(192)	(29)
Impact of change in U.S. corporate tax rate	83	0	0
Total Federal deferred taxes	88	(192)	(29)
Provision for income taxes as shown in the Statement of Earnings	$ 247	$ 119	$ 195

Income Taxes - Operating and ca

Income Taxes - Operating and capital loss carryforwards available (Details) - Dec. 31, 2017 £ in Millions, $ in Millions		USD ($)	GBP (£)
U.S. | Expiring 2018 - 2022
Operating and capital loss carryforwards [Line Items]
Operating loss carryforwards		$ 130
U.S. | Capital loss carryforward | Expiring 2022
Operating and capital loss carryforwards [Line Items]
Capital loss carryforwards		109
United Kingdom
Operating and capital loss carryforwards [Line Items]
Operating loss carryforwards	[1]	$ 252	£ 186
[1]	£186 million

Income Taxes - Significant comp

Income Taxes - Significant components of deferred tax assets and liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Deferred tax assets:
Federal net operating loss carryforwards	$ 27	$ 50
Foreign underwriting losses	80	120
Capital loss carryforwards	32	83
Insurance claims and reserves	694	801
Employee benefits	84	131
Other, net	45	80
Total deferred tax assets before valuation allowance	962	1,265
Valuation allowance against deferred tax assets	(109)	(173)
Total deferred tax assets	853	1,092
Deferred tax liabilities:
Investment securities	(341)	(307)
Deferred policy acquisition costs	(202)	(352)
Insurance claims and reserves transition liability	(128)	0
Real estate, property and equipment	(35)	(45)
Total deferred tax liabilities	(706)	(704)
Net deferred tax asset (liability)	147	388
Excluding Unrealized Gains
Deferred tax assets:
Federal net operating loss carryforwards	27	50
Foreign underwriting losses	80	120
Capital loss carryforwards	32	83
Insurance claims and reserves	665	774
Employee benefits	84	131
Other, net	48	85
Total deferred tax assets before valuation allowance	936	1,243
Valuation allowance against deferred tax assets	(109)	(173)
Total deferred tax assets	827	1,070
Deferred tax liabilities:
Investment securities	(1)	29
Deferred policy acquisition costs	(293)	(448)
Insurance claims and reserves transition liability	(128)	0
Real estate, property and equipment	(35)	(45)
Total deferred tax liabilities	(457)	(464)
Net deferred tax asset (liability)	370	606
Impact of Unrealized Gains
Deferred tax assets:
Federal net operating loss carryforwards	0	0
Foreign underwriting losses	0	0
Capital loss carryforwards	0	0
Insurance claims and reserves	29	27
Employee benefits	0	0
Other, net	(3)	(5)
Total deferred tax assets before valuation allowance	26	22
Valuation allowance against deferred tax assets	0	0
Total deferred tax assets	26	22
Deferred tax liabilities:
Investment securities	(340)	(336)
Deferred policy acquisition costs	91	96
Insurance claims and reserves transition liability	0	0
Real estate, property and equipment	0	0
Total deferred tax liabilities	(249)	(240)
Net deferred tax asset (liability)	$ (223)	$ (218)

Income Taxes - Progression of t

Income Taxes - Progression of the liability for uncertain tax positions, excluding interest and penalties (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Progression of the liability for uncertain tax positions, excluding interest and penalties
Balance at January 1	$ 1	$ 1	$ 0
Additions for tax positions of prior years	0	0	1
Reductions for tax positions of prior years	0	0	0
Additions for tax positions of current year	0	0	0
Settlements	(1)	0	0
Balance at December 31	$ 0	$ 1	$ 1

Contingencies - Narrative (Deta

Contingencies - Narrative (Details) - USD ($) $ in Millions	Dec. 24, 2015	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Loss Contingencies [Line Items]
Reinsurance recoverables on asbestos and environmental reserves, net of allowance					$ 2,957	$ 2,302	$ 2,201	$ 2,227
Property and Casualty Group
Loss Contingencies [Line Items]
Increase in asbestos and environmental reserves		$ 89	$ 36	$ 67
Liability for asbestos and environmental reserves					528
Former railroad and manufacturing operations
Loss Contingencies [Line Items]
Increase in asbestos and environmental reserves		$ 24	$ 5	$ 12
American Premier and its subsidiaries
Loss Contingencies [Line Items]
Liability for environmental and other claims					81
GAFRI
Loss Contingencies [Line Items]
Liability for environmental and other claims					8
Run-off long-term care insurance business
Loss Contingencies [Line Items]
Contingent capital support agreement term	5 years
A&E reserves | Property and Casualty Group
Loss Contingencies [Line Items]
Reinsurance recoverables on asbestos and environmental reserves, net of allowance					$ 125

Quarterly Operating Results (90

Quarterly Operating Results (Unaudited) - Narrative (Details) - USD ($) $ in Millions	3 Months Ended							12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Quarterly Operating Results (Unaudited) [Line Items]
Pretax catastrophe losses		$ 107						$ 140	$ 55
Income tax expense (benefit)								247	119	$ 195
Property and casualty insurance | Other lines
Quarterly Operating Results (Unaudited) [Line Items]
Special charges to increase asbestos and environmental reserves		89				$ 36		89	36	67
Favorable reserve development related to certain lines of business within subsidiaries in connection with a reinsurance to close agreement								18
Special charges related to the exit of certain lines of business within subsidiaries							$ 65		65
Property and casualty insurance | Other lines | Increased insurance loss reserves related to medical malpractice and general liability lines
Quarterly Operating Results (Unaudited) [Line Items]
Special charges related to the exit of certain lines of business within subsidiaries							57
Other
Quarterly Operating Results (Unaudited) [Line Items]
Special charges to increase asbestos and environmental reserves								24	5	12
Write off of deferred debt issuance cost due to the retirement of debt		4	$ 7							4
Make-whole premium, settlement of interest rate swap and write off of deferred debt issuance cost included in the loss on the retirement of debt	$ 40							51
Other | Former railroad and manufacturing operations
Quarterly Operating Results (Unaudited) [Line Items]
Special charges to increase asbestos and environmental reserves		$ 24				$ 5
Neon Capital Limited
Quarterly Operating Results (Unaudited) [Line Items]
Income tax expense (benefit)	(56)				$ (111)				(48)
Neon Capital Limited | Property and casualty insurance
Quarterly Operating Results (Unaudited) [Line Items]
Favorable reserve development related to certain lines of business within subsidiaries in connection with a reinsurance to close agreement	42
Neon Capital Limited | Property and casualty insurance | Other lines
Quarterly Operating Results (Unaudited) [Line Items]
Favorable reserve development related to certain lines of business within subsidiaries in connection with a reinsurance to close agreement	18
Special charges related to the exit of certain lines of business within subsidiaries									65
Neon Capital Limited | Neon Capital Limited | Current lines
Quarterly Operating Results (Unaudited) [Line Items]
Favorable reserve development related to certain lines of business within subsidiaries in connection with a reinsurance to close agreement	24
AFG
Quarterly Operating Results (Unaudited) [Line Items]
Income tax expense (benefit)	$ (56)				$ (177)			$ 247	119	195
Real estate investment | Property and casualty insurance
Quarterly Operating Results (Unaudited) [Line Items]
Pretax income from the sale of real estate properties included in other income				$ 13			$ 32		$ 32	$ 66

Quarterly Operating Results (91

Quarterly Operating Results (Unaudited) - Quarterly results of consolidated operations (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Condensed Statement of Earnings
Revenues	$ 1,808	$ 1,835	$ 1,646	$ 1,576	$ 1,737	$ 1,705	$ 1,581	$ 1,475	$ 6,865	$ 6,498	$ 6,145
Net earnings, including noncontrolling interests	166	11	145	155	388	113	63	104	477	668	370
Net earnings attributable to shareholders	$ 166	$ 11	$ 145	$ 153	$ 385	$ 109	$ 54	$ 101	$ 475	$ 649	$ 352
Earnings Attributable to Shareholders per Common Share:
Basic (USD per share)	$ 1.88	$ 0.13	$ 1.64	$ 1.76	$ 4.43	$ 1.25	$ 0.63	$ 1.16	$ 5.40	$ 7.47	$ 4.02
Diluted (USD per share)	$ 1.84	$ 0.13	$ 1.61	$ 1.72	$ 4.33	$ 1.23	$ 0.62	$ 1.14	$ 5.28	$ 7.33	$ 3.94
Average number of Common Shares:
Basic (shares)	88.2	88.1	87.8	87.2	86.9	86.9	86.8	86.9	87.8	86.9	87.6
Diluted (shares)	90.1	90	89.8	89.3	88.8	88.5	88.4	88.5	89.8	88.5	89.4

Quarterly Operating Results (92

Quarterly Operating Results (Unaudited) - Realized gains, favorable (adverse) prior year development of the liability for losses and LAE and the impact of derivatives related to Fixed-indexed annuities (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016
Realized gains (losses) and favorable (adverse) development on unpaid loss and loss adjustment expenses
Realized Gains (Losses) on Securities and Subsidiaries	$ 6	$ (12)	$ 8	$ 3	$ 51	$ 2	$ (14)	$ (18)	$ 5	$ 21
Prior Year Development Favorable (Adverse)	66	(52)	22	28	(10)	(22)	(28)	28	64	(32)
Impact of derivatives related to FIAs	$ (11)	$ (4)	$ (16)	$ (2)	$ 29	$ 1	$ (26)	$ (31)	$ (33)	$ (27)

Insurance - Narrative (Details)

Insurance - Narrative (Details) - USD ($) $ in Millions	3 Months Ended				12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Sep. 30, 2016	Jun. 30, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Insurance [Line Items]
Carrying value of cash and securities owned by U.S.-based insurance subsidiaries on deposit	$ 1,080				$ 1,080
Carrying value of cash and securities owned by insurance subsidiaries on deposit in support of underwriting activities at Lloyd's	205				205
Undrawn letters of credit	447				447
Undrawn letters of credit, collateralized	0				$ 0
Workers' compensation insurance discount rate					4.50%	4.50%
Workers' compensation insurance discount, which has reduced the liability for unpaid losses and loss adjustment expenses	15				$ 15	$ 16
Long-term care insurance reserves, net of reinsurance recoverables	39				39	37
Investment in Federal Home Loan Bank capital stock	44				44
Repayments under funding agreements with the Federal Home Loan Bank	64
Advances from Federal Home Loan Bank	871				$ 871
Description of variable rate basis					LIBOR
Repayments of advances from Federal Home Loan Bank due in next twelve months	285				$ 285
Repayments of advances from Federal Home Loan Bank due in year three	586				586
Fair value of fixed maturity investments held as collateral by the Federal Home Loan Bank	1,040				1,040
Interest on advances from Federal Home Loan Bank					14	8	$ 3
Maximum amount of dividends available to be paid by insurance subsidiaries to AFG without prior approval of regulatory authorities	826				826
Dividends on Common Stock					(421)	(187)	(178)
Aggregate guaranteed minimum death benefit value on variable annuity polices in force	15				15	20
Minimum
Insurance [Line Items]
Dividends payments without violating the most restrictive debt covenants, minimum	1,000				$ 1,000
Minimum | LIBOR
Insurance [Line Items]
FHLB advances, basis spread on variable rate					0.03%
Maximum | LIBOR
Insurance [Line Items]
FHLB advances, basis spread on variable rate					0.35%
Average | LIBOR
Insurance [Line Items]
FHLB advances, basis spread on variable rate					1.75%
FHLB, advances, refinanced terms
Insurance [Line Items]
Advances from Federal Home Loan Bank	831				$ 831
Catastrophe Bonds
Insurance [Line Items]
Catastrophe reinsurance coverage, excess retention percentage					95.00%
Catastrophe reinsurance coverage, excess retention amount					$ 200
Catastrophe reinsurance coverage, retention amount					100
Catastrophe reinsurance coverage, annual cost					11
Life insurance
Insurance [Line Items]
Life insurance in force, ceded premiums	8,320				8,320	10,220
Life insurance in force, direct premiums	12,050				12,050	13,490
Life written premiums ceded					28	31	40
Reinsurance recoveries					35	41	50
Variable annuities | Maximum
Insurance [Line Items]
Death benefits paid in excess of the variable annuity account balances (are less than in 2014, 2015 and 2016)					1	1	1
Property and casualty insurance | Other lines
Insurance [Line Items]
Favorable reserve development related to certain lines of business within subsidiaries in connection with a reinsurance to close agreement					18
Special charges to increase asbestos and environmental reserves		$ 89	$ 36		$ 89	36	$ 67
Special charges related to the exit of certain lines of business within subsidiaries				$ 65		65
Property and casualty insurance | Other lines | Increased insurance loss reserves related to medical malpractice and general liability lines
Insurance [Line Items]
Special charges related to the exit of certain lines of business within subsidiaries				$ 57
Neon Capital Limited | Property and casualty insurance
Insurance [Line Items]
Favorable reserve development related to certain lines of business within subsidiaries in connection with a reinsurance to close agreement	42
Neon Capital Limited | Property and casualty insurance | Other lines
Insurance [Line Items]
Favorable reserve development related to certain lines of business within subsidiaries in connection with a reinsurance to close agreement	18
Special charges related to the exit of certain lines of business within subsidiaries						$ 65
Neon Capital Limited | Property and casualty insurance | Other lines | Reinsurance to close agreement
Insurance [Line Items]
Favorable reserve development related to certain lines of business within subsidiaries in connection with a reinsurance to close agreement	18
Neon Capital Limited | Neon Capital Limited | Current lines
Insurance [Line Items]
Favorable reserve development related to certain lines of business within subsidiaries in connection with a reinsurance to close agreement	$ 24

Insurance - Analysis of changes

Insurance - Analysis of changes in the liability for losses and loss adjustment expenses, net of reinsurance (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016		Dec. 31, 2015
Analysis of changes in the liability for losses and loss adjustment expenses, net of reinsurance
Balance at beginning of period				$ 8,563				$ 8,127	$ 8,563	$ 8,127		$ 7,872
Less reinsurance recoverables, net of allowance				2,302				2,201	2,302	2,201		2,227
Net liability at beginning of period				6,261				5,926	6,261	5,926		5,645
Liability for losses and loss adjustment expenses, period increase (decrease) [Abstract]
Provision for losses and LAE occurring in the current year									3,019	2,730		2,662
Net increase (decrease) in the provision for claims of prior years:
Provision for claims of prior years related to special A&E charges, Neon exited lines development and other	$ (66)	$ 52	$ (22)	$ (28)	$ 10	$ 22	$ 28	$ (28)	(64)	32
Total losses and LAE incurred									2,955	2,762		2,695
Payments for losses and LAE of:
Current year									(942)	(841)		(828)
Prior years									(1,586)	(1,512)		(1,575)
Total payments									(2,528)	(2,353)		(2,403)
Reserves of businesses acquired									0	(40)	[1]	0
Foreign currency translation and other									33	(34)		(11)
Net liability at end of period	6,721				6,261				6,721	6,261		5,926
Add back reinsurance recoverables, net of allowance	2,957				2,302				2,957	2,302		2,201
Gross unpaid losses and LAE included in the balance sheet	$ 9,678				$ 8,563				9,678	8,563		8,127
Special A&E charges
Net increase (decrease) in the provision for claims of prior years:
Provision for claims of prior years related to special A&E charges, Neon exited lines development and other									89	36		67
Neon exited lines charge
Net increase (decrease) in the provision for claims of prior years:
Provision for claims of prior years related to special A&E charges, Neon exited lines development and other									(18)	57		0
Other
Net increase (decrease) in the provision for claims of prior years:
Provision for claims of prior years related to special A&E charges, Neon exited lines development and other									$ (135)	$ (61)		$ (34)
[1]	Reflects the 2016 reinsurance to close transactions at Neon (discussed below).

Insurance - Reconciliation of i

Insurance - Reconciliation of incurred and paid claims development information to the aggregate carrying amount of the liability for unpaid losses and LAE (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Total reserves, net of reinsurance	$ 6,721	$ 6,261	$ 5,926	$ 5,645
Add back reinsurance recoverables, net of allowance	(2,957)	(2,302)	(2,201)	(2,227)
Gross unpaid losses and LAE included in the balance sheet	9,678	$ 8,563	$ 8,127	$ 7,872
Property and casualty insurance
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Specialty unpaid losses and LAE, net of reinsurance	5,198
Other unpaid losses and LAE, net of reinsurance	1,523
Unallocated LAE	326
Total reserves, net of reinsurance	6,721
Add back reinsurance recoverables, net of allowance	2,957
Gross unpaid losses and LAE included in the balance sheet	9,678
Property and casualty insurance | Reserves for foreign operations:
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Other unpaid losses and LAE, net of reinsurance	269
Property and casualty insurance | A&E reserves
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Other unpaid losses and LAE, net of reinsurance	403
Property and casualty insurance | Other
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Other unpaid losses and LAE, net of reinsurance	45
Property and casualty insurance | Property and transportation
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Specialty unpaid losses and LAE, net of reinsurance	1,069
Property and casualty insurance | Specialty casualty
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Specialty unpaid losses and LAE, net of reinsurance	3,630
Property and casualty insurance | Specialty financial
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Specialty unpaid losses and LAE, net of reinsurance	221
Property and casualty insurance | Other specialty
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Specialty unpaid losses and LAE, net of reinsurance	278
Neon Capital Limited | Property and casualty insurance | Reserves for foreign operations:
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Other unpaid losses and LAE, net of reinsurance	$ 480

Insurance - Short-duration insu

Insurance - Short-duration insurance contracts, claims development (Details) - Property and casualty insurance $ in Millions		Dec. 31, 2017USD ($)claim	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)	Dec. 31, 2014USD ($)	Dec. 31, 2013USD ($)	Dec. 31, 2012USD ($)	Dec. 31, 2011USD ($)	Dec. 31, 2010USD ($)	Dec. 31, 2009USD ($)	Dec. 31, 2008USD ($)
Claims Development [Line Items]
Incurred Claims and Allocated LAE, Net of Reinsurance		$ 19,503
Cumulative Paid Claims and Allocated LAE, Net of Reinsurance		14,838
Unpaid losses and LAE — 11th year and prior (excluding unallocated LAE)		533
Unpaid losses and LAE, net of reinsurance (excluding unallocated LAE)		5,198
Accident Year 2008
Claims Development [Line Items]
Incurred Claims and Allocated LAE, Net of Reinsurance		1,950	$ 1,951	$ 1,947	$ 1,953	$ 1,955	$ 1,978	$ 1,971	$ 1,987	$ 2,018	$ 2,067
Total IBNR Plus Expected Development on Reported Claims		$ 46
Cumulative Number of Reported Claims | claim		244,447
Cumulative Paid Claims and Allocated LAE, Net of Reinsurance		$ 1,866	1,847	1,828	1,803	1,765	1,701	1,607	1,459	1,230	627
Cumulative Percentage Paid of Incurred Claims and Allocated LAE, Net of Reinsurance	[1]	95.70%
Accident Year 2009
Claims Development [Line Items]
Incurred Claims and Allocated LAE, Net of Reinsurance		$ 1,529	1,539	1,543	1,545	1,552	1,566	1,596	1,607	1,624
Total IBNR Plus Expected Development on Reported Claims		$ 58
Cumulative Number of Reported Claims | claim		221,165
Cumulative Paid Claims and Allocated LAE, Net of Reinsurance		$ 1,435	1,424	1,404	1,370	1,308	1,216	1,079	871	509
Cumulative Percentage Paid of Incurred Claims and Allocated LAE, Net of Reinsurance	[1]	93.90%
Accident Year 2010
Claims Development [Line Items]
Incurred Claims and Allocated LAE, Net of Reinsurance		$ 1,690	1,698	1,698	1,710	1,690	1,705	1,710	1,724
Total IBNR Plus Expected Development on Reported Claims		$ 75
Cumulative Number of Reported Claims | claim		215,418
Cumulative Paid Claims and Allocated LAE, Net of Reinsurance		$ 1,580	1,562	1,536	1,485	1,387	1,220	1,005	576
Cumulative Percentage Paid of Incurred Claims and Allocated LAE, Net of Reinsurance	[1]	93.50%
Accident Year 2011
Claims Development [Line Items]
Incurred Claims and Allocated LAE, Net of Reinsurance		$ 1,859	1,866	1,861	1,871	1,849	1,848	1,840
Total IBNR Plus Expected Development on Reported Claims		$ 98
Cumulative Number of Reported Claims | claim		207,643
Cumulative Paid Claims and Allocated LAE, Net of Reinsurance		$ 1,711	1,682	1,629	1,534	1,389	1,181	609
Cumulative Percentage Paid of Incurred Claims and Allocated LAE, Net of Reinsurance	[1]	92.00%
Accident Year 2012
Claims Development [Line Items]
Incurred Claims and Allocated LAE, Net of Reinsurance		$ 1,941	1,955	1,947	1,946	1,952	1,970
Total IBNR Plus Expected Development on Reported Claims		$ 142
Cumulative Number of Reported Claims | claim		217,516
Cumulative Paid Claims and Allocated LAE, Net of Reinsurance		$ 1,735	1,675	1,579	1,418	1,214	824
Cumulative Percentage Paid of Incurred Claims and Allocated LAE, Net of Reinsurance	[1]	89.40%
Accident Year 2013
Claims Development [Line Items]
Incurred Claims and Allocated LAE, Net of Reinsurance		$ 2,000	1,996	2,000	2,011	2,036
Total IBNR Plus Expected Development on Reported Claims		$ 168
Cumulative Number of Reported Claims | claim		219,940
Cumulative Paid Claims and Allocated LAE, Net of Reinsurance		$ 1,714	1,617	1,443	1,214	697
Cumulative Percentage Paid of Incurred Claims and Allocated LAE, Net of Reinsurance	[1]	85.70%
Accident Year 2014
Claims Development [Line Items]
Incurred Claims and Allocated LAE, Net of Reinsurance		$ 2,038	2,040	2,050	2,083
Total IBNR Plus Expected Development on Reported Claims		$ 272
Cumulative Number of Reported Claims | claim		218,032
Cumulative Paid Claims and Allocated LAE, Net of Reinsurance		$ 1,588	1,422	1,173	594
Cumulative Percentage Paid of Incurred Claims and Allocated LAE, Net of Reinsurance	[1]	77.90%
Accident Year 2015
Claims Development [Line Items]
Incurred Claims and Allocated LAE, Net of Reinsurance		$ 2,040	2,046	2,114
Total IBNR Plus Expected Development on Reported Claims		$ 363
Cumulative Number of Reported Claims | claim		225,000
Cumulative Paid Claims and Allocated LAE, Net of Reinsurance		$ 1,403	1,128	619
Cumulative Percentage Paid of Incurred Claims and Allocated LAE, Net of Reinsurance	[1]	68.80%
Accident Year 2016
Claims Development [Line Items]
Incurred Claims and Allocated LAE, Net of Reinsurance		$ 2,082	2,116
Total IBNR Plus Expected Development on Reported Claims		$ 593
Cumulative Number of Reported Claims | claim		216,248
Cumulative Paid Claims and Allocated LAE, Net of Reinsurance		$ 1,098	576
Cumulative Percentage Paid of Incurred Claims and Allocated LAE, Net of Reinsurance	[1]	52.70%
Accident Year 2017
Claims Development [Line Items]
Incurred Claims and Allocated LAE, Net of Reinsurance		$ 2,374
Total IBNR Plus Expected Development on Reported Claims		$ 1,119
Cumulative Number of Reported Claims | claim		210,970
Cumulative Paid Claims and Allocated LAE, Net of Reinsurance		$ 708
Cumulative Percentage Paid of Incurred Claims and Allocated LAE, Net of Reinsurance	[1]	29.80%
Excludes short-duration insurance contracts detail for accident years not separately presented
Claims Development [Line Items]
Unpaid losses and LAE, net of reinsurance (excluding unallocated LAE)		$ 4,665
Property and transportation
Claims Development [Line Items]
Incurred Claims and Allocated LAE, Net of Reinsurance		8,029
Cumulative Paid Claims and Allocated LAE, Net of Reinsurance		6,980
Unpaid losses and LAE — 11th year and prior (excluding unallocated LAE)		20
Unpaid losses and LAE, net of reinsurance (excluding unallocated LAE)		1,069
Property and transportation | Accident Year 2008
Claims Development [Line Items]
Incurred Claims and Allocated LAE, Net of Reinsurance		854	854	856	855	854	856	853	852	871	923
Total IBNR Plus Expected Development on Reported Claims		$ 1
Cumulative Number of Reported Claims | claim		157,164
Cumulative Paid Claims and Allocated LAE, Net of Reinsurance		$ 848	847	846	846	835	824	799	761	706	352
Cumulative Percentage Paid of Incurred Claims and Allocated LAE, Net of Reinsurance	[2]	99.30%
Property and transportation | Accident Year 2009
Claims Development [Line Items]
Incurred Claims and Allocated LAE, Net of Reinsurance		$ 508	508	508	511	511	516	523	506	526
Total IBNR Plus Expected Development on Reported Claims		$ 3
Cumulative Number of Reported Claims | claim		140,532
Cumulative Paid Claims and Allocated LAE, Net of Reinsurance		$ 502	499	497	493	479	456	413	348	229
Cumulative Percentage Paid of Incurred Claims and Allocated LAE, Net of Reinsurance	[2]	98.80%
Property and transportation | Accident Year 2010
Claims Development [Line Items]
Incurred Claims and Allocated LAE, Net of Reinsurance		$ 680	683	679	679	676	668	662	702
Total IBNR Plus Expected Development on Reported Claims		$ 6
Cumulative Number of Reported Claims | claim		140,634
Cumulative Paid Claims and Allocated LAE, Net of Reinsurance		$ 669	665	660	649	618	556	505	328
Cumulative Percentage Paid of Incurred Claims and Allocated LAE, Net of Reinsurance	[2]	98.40%
Property and transportation | Accident Year 2011
Claims Development [Line Items]
Incurred Claims and Allocated LAE, Net of Reinsurance		$ 865	868	856	845	831	816	830
Total IBNR Plus Expected Development on Reported Claims		$ 10
Cumulative Number of Reported Claims | claim		140,418
Cumulative Paid Claims and Allocated LAE, Net of Reinsurance		$ 847	840	821	787	742	679	373
Cumulative Percentage Paid of Incurred Claims and Allocated LAE, Net of Reinsurance	[2]	97.90%
Property and transportation | Accident Year 2012
Claims Development [Line Items]
Incurred Claims and Allocated LAE, Net of Reinsurance		$ 918	922	909	897	884	890
Total IBNR Plus Expected Development on Reported Claims		$ 19
Cumulative Number of Reported Claims | claim		146,630
Cumulative Paid Claims and Allocated LAE, Net of Reinsurance		$ 883	868	841	793	725	582
Cumulative Percentage Paid of Incurred Claims and Allocated LAE, Net of Reinsurance	[2]	96.20%
Property and transportation | Accident Year 2013
Claims Development [Line Items]
Incurred Claims and Allocated LAE, Net of Reinsurance		$ 910	908	902	898	911
Total IBNR Plus Expected Development on Reported Claims		$ 22
Cumulative Number of Reported Claims | claim		142,249
Cumulative Paid Claims and Allocated LAE, Net of Reinsurance		$ 862	831	784	721	449
Cumulative Percentage Paid of Incurred Claims and Allocated LAE, Net of Reinsurance	[2]	94.70%
Property and transportation | Accident Year 2014
Claims Development [Line Items]
Incurred Claims and Allocated LAE, Net of Reinsurance		$ 843	841	852	868
Total IBNR Plus Expected Development on Reported Claims		$ 38
Cumulative Number of Reported Claims | claim		136,882
Cumulative Paid Claims and Allocated LAE, Net of Reinsurance		$ 765	711	646	337
Cumulative Percentage Paid of Incurred Claims and Allocated LAE, Net of Reinsurance	[2]	90.70%
Property and transportation | Accident Year 2015
Claims Development [Line Items]
Incurred Claims and Allocated LAE, Net of Reinsurance		$ 798	804	842
Total IBNR Plus Expected Development on Reported Claims		$ 54
Cumulative Number of Reported Claims | claim		135,029
Cumulative Paid Claims and Allocated LAE, Net of Reinsurance		$ 683	595	367
Cumulative Percentage Paid of Incurred Claims and Allocated LAE, Net of Reinsurance	[2]	85.60%
Property and transportation | Accident Year 2016
Claims Development [Line Items]
Incurred Claims and Allocated LAE, Net of Reinsurance		$ 740	771
Total IBNR Plus Expected Development on Reported Claims		$ 110
Cumulative Number of Reported Claims | claim		122,112
Cumulative Paid Claims and Allocated LAE, Net of Reinsurance		$ 534	299
Cumulative Percentage Paid of Incurred Claims and Allocated LAE, Net of Reinsurance	[2]	72.20%
Property and transportation | Accident Year 2017
Claims Development [Line Items]
Incurred Claims and Allocated LAE, Net of Reinsurance		$ 913
Total IBNR Plus Expected Development on Reported Claims		$ 273
Cumulative Number of Reported Claims | claim		128,455
Cumulative Paid Claims and Allocated LAE, Net of Reinsurance		$ 387
Cumulative Percentage Paid of Incurred Claims and Allocated LAE, Net of Reinsurance	[2]	42.40%
Property and transportation | Excludes short-duration insurance contracts detail for accident years not separately presented
Claims Development [Line Items]
Unpaid losses and LAE, net of reinsurance (excluding unallocated LAE)		$ 1,049
Specialty casualty
Claims Development [Line Items]
Incurred Claims and Allocated LAE, Net of Reinsurance		9,355
Cumulative Paid Claims and Allocated LAE, Net of Reinsurance		6,155
Unpaid losses and LAE — 11th year and prior (excluding unallocated LAE)		430
Unpaid losses and LAE, net of reinsurance (excluding unallocated LAE)		3,630
Specialty casualty | Accident Year 2008
Claims Development [Line Items]
Incurred Claims and Allocated LAE, Net of Reinsurance		854	855	849	855	856	871	860	874	891	905
Total IBNR Plus Expected Development on Reported Claims		$ 41
Cumulative Number of Reported Claims | claim		59,991
Cumulative Paid Claims and Allocated LAE, Net of Reinsurance		$ 782	768	751	727	702	653	588	490	355	162
Cumulative Percentage Paid of Incurred Claims and Allocated LAE, Net of Reinsurance	[3]	91.60%
Specialty casualty | Accident Year 2009
Claims Development [Line Items]
Incurred Claims and Allocated LAE, Net of Reinsurance		$ 803	807	812	811	816	826	845	867	864
Total IBNR Plus Expected Development on Reported Claims		$ 48
Cumulative Number of Reported Claims | claim		53,192
Cumulative Paid Claims and Allocated LAE, Net of Reinsurance		$ 722	713	698	673	636	575	494	366	160
Cumulative Percentage Paid of Incurred Claims and Allocated LAE, Net of Reinsurance	[3]	89.90%
Specialty casualty | Accident Year 2010
Claims Development [Line Items]
Incurred Claims and Allocated LAE, Net of Reinsurance		$ 842	845	846	856	842	864	863	847
Total IBNR Plus Expected Development on Reported Claims		$ 65
Cumulative Number of Reported Claims | claim		52,855
Cumulative Paid Claims and Allocated LAE, Net of Reinsurance		$ 748	734	712	676	623	539	393	179
Cumulative Percentage Paid of Incurred Claims and Allocated LAE, Net of Reinsurance	[3]	88.80%
Specialty casualty | Accident Year 2011
Claims Development [Line Items]
Incurred Claims and Allocated LAE, Net of Reinsurance		$ 806	808	814	828	819	831	831
Total IBNR Plus Expected Development on Reported Claims		$ 73
Cumulative Number of Reported Claims | claim		50,851
Cumulative Paid Claims and Allocated LAE, Net of Reinsurance		$ 694	674	643	595	506	369	165
Cumulative Percentage Paid of Incurred Claims and Allocated LAE, Net of Reinsurance	[3]	86.10%
Specialty casualty | Accident Year 2012
Claims Development [Line Items]
Incurred Claims and Allocated LAE, Net of Reinsurance		$ 849	855	859	859	865	874
Total IBNR Plus Expected Development on Reported Claims		$ 104
Cumulative Number of Reported Claims | claim		49,836
Cumulative Paid Claims and Allocated LAE, Net of Reinsurance		$ 696	658	596	495	368	163
Cumulative Percentage Paid of Incurred Claims and Allocated LAE, Net of Reinsurance	[3]	82.00%
Specialty casualty | Accident Year 2013
Claims Development [Line Items]
Incurred Claims and Allocated LAE, Net of Reinsurance		$ 913	910	915	921	938
Total IBNR Plus Expected Development on Reported Claims		$ 132
Cumulative Number of Reported Claims | claim		49,412
Cumulative Paid Claims and Allocated LAE, Net of Reinsurance		$ 698	638	530	377	171
Cumulative Percentage Paid of Incurred Claims and Allocated LAE, Net of Reinsurance	[3]	76.50%
Specialty casualty | Accident Year 2014
Claims Development [Line Items]
Incurred Claims and Allocated LAE, Net of Reinsurance		$ 982	984	984	1,011
Total IBNR Plus Expected Development on Reported Claims		$ 202
Cumulative Number of Reported Claims | claim		52,167
Cumulative Paid Claims and Allocated LAE, Net of Reinsurance		$ 659	556	398	182
Cumulative Percentage Paid of Incurred Claims and Allocated LAE, Net of Reinsurance	[3]	67.10%
Specialty casualty | Accident Year 2015
Claims Development [Line Items]
Incurred Claims and Allocated LAE, Net of Reinsurance		$ 1,022	1,023	1,057
Total IBNR Plus Expected Development on Reported Claims		$ 268
Cumulative Number of Reported Claims | claim		52,846
Cumulative Paid Claims and Allocated LAE, Net of Reinsurance		$ 560	398	170
Cumulative Percentage Paid of Incurred Claims and Allocated LAE, Net of Reinsurance	[3]	54.80%
Specialty casualty | Accident Year 2016
Claims Development [Line Items]
Incurred Claims and Allocated LAE, Net of Reinsurance		$ 1,098	1,105
Total IBNR Plus Expected Development on Reported Claims		$ 426
Cumulative Number of Reported Claims | claim		50,652
Cumulative Paid Claims and Allocated LAE, Net of Reinsurance		$ 404	181
Cumulative Percentage Paid of Incurred Claims and Allocated LAE, Net of Reinsurance	[3]	36.80%
Specialty casualty | Accident Year 2017
Claims Development [Line Items]
Incurred Claims and Allocated LAE, Net of Reinsurance		$ 1,186
Total IBNR Plus Expected Development on Reported Claims		$ 715
Cumulative Number of Reported Claims | claim		46,399
Cumulative Paid Claims and Allocated LAE, Net of Reinsurance		$ 192
Cumulative Percentage Paid of Incurred Claims and Allocated LAE, Net of Reinsurance	[3]	16.20%
Specialty casualty | Excludes short-duration insurance contracts detail for accident years not separately presented
Claims Development [Line Items]
Unpaid losses and LAE, net of reinsurance (excluding unallocated LAE)		$ 3,200
Specialty financial
Claims Development [Line Items]
Incurred Claims and Allocated LAE, Net of Reinsurance		1,624
Cumulative Paid Claims and Allocated LAE, Net of Reinsurance		1,403
Unpaid losses and LAE — 11th year and prior (excluding unallocated LAE)		0
Unpaid losses and LAE, net of reinsurance (excluding unallocated LAE)		221
Specialty financial | Accident Year 2008
Claims Development [Line Items]
Incurred Claims and Allocated LAE, Net of Reinsurance		199	198	197	198	199	203	209	212	207	190
Total IBNR Plus Expected Development on Reported Claims		$ 1
Cumulative Number of Reported Claims | claim		27,292
Cumulative Paid Claims and Allocated LAE, Net of Reinsurance		$ 197	194	194	193	191	189	189	185	153	103
Cumulative Percentage Paid of Incurred Claims and Allocated LAE, Net of Reinsurance	[4]	99.00%
Specialty financial | Accident Year 2009
Claims Development [Line Items]
Incurred Claims and Allocated LAE, Net of Reinsurance		$ 185	186	187	186	188	184	187	193	193
Total IBNR Plus Expected Development on Reported Claims		$ 0
Cumulative Number of Reported Claims | claim		27,441
Cumulative Paid Claims and Allocated LAE, Net of Reinsurance		$ 186	186	185	182	171	166	157	145	112
Cumulative Percentage Paid of Incurred Claims and Allocated LAE, Net of Reinsurance	[4]	100.50%
Specialty financial | Accident Year 2010
Claims Development [Line Items]
Incurred Claims and Allocated LAE, Net of Reinsurance		$ 128	130	133	135	133	133	146	139
Total IBNR Plus Expected Development on Reported Claims		$ 2
Cumulative Number of Reported Claims | claim		21,929
Cumulative Paid Claims and Allocated LAE, Net of Reinsurance		$ 127	128	131	133	122	104	93	61
Cumulative Percentage Paid of Incurred Claims and Allocated LAE, Net of Reinsurance	[4]	99.20%
Specialty financial | Accident Year 2011
Claims Development [Line Items]
Incurred Claims and Allocated LAE, Net of Reinsurance		$ 144	146	148	155	157	158	140
Total IBNR Plus Expected Development on Reported Claims		$ 11
Cumulative Number of Reported Claims | claim		16,374
Cumulative Paid Claims and Allocated LAE, Net of Reinsurance		$ 133	132	131	124	116	113	59
Cumulative Percentage Paid of Incurred Claims and Allocated LAE, Net of Reinsurance	[4]	92.40%
Specialty financial | Accident Year 2012
Claims Development [Line Items]
Incurred Claims and Allocated LAE, Net of Reinsurance		$ 135	137	139	151	163	164
Total IBNR Plus Expected Development on Reported Claims		$ 11
Cumulative Number of Reported Claims | claim		21,050
Cumulative Paid Claims and Allocated LAE, Net of Reinsurance		$ 126	121	117	109	104	71
Cumulative Percentage Paid of Incurred Claims and Allocated LAE, Net of Reinsurance	[4]	93.30%
Specialty financial | Accident Year 2013
Claims Development [Line Items]
Incurred Claims and Allocated LAE, Net of Reinsurance		$ 127	131	137	145	141
Total IBNR Plus Expected Development on Reported Claims		$ 9
Cumulative Number of Reported Claims | claim		28,279
Cumulative Paid Claims and Allocated LAE, Net of Reinsurance		$ 117	114	107	100	70
Cumulative Percentage Paid of Incurred Claims and Allocated LAE, Net of Reinsurance	[4]	92.10%
Specialty financial | Accident Year 2014
Claims Development [Line Items]
Incurred Claims and Allocated LAE, Net of Reinsurance		$ 154	156	157	146
Total IBNR Plus Expected Development on Reported Claims		$ 16
Cumulative Number of Reported Claims | claim		28,983
Cumulative Paid Claims and Allocated LAE, Net of Reinsurance		$ 128	125	108	62
Cumulative Percentage Paid of Incurred Claims and Allocated LAE, Net of Reinsurance	[4]	83.10%
Specialty financial | Accident Year 2015
Claims Development [Line Items]
Incurred Claims and Allocated LAE, Net of Reinsurance		$ 157	159	156
Total IBNR Plus Expected Development on Reported Claims		$ 21
Cumulative Number of Reported Claims | claim		37,125
Cumulative Paid Claims and Allocated LAE, Net of Reinsurance		$ 129	109	72
Cumulative Percentage Paid of Incurred Claims and Allocated LAE, Net of Reinsurance	[4]	82.20%
Specialty financial | Accident Year 2016
Claims Development [Line Items]
Incurred Claims and Allocated LAE, Net of Reinsurance		$ 183	179
Total IBNR Plus Expected Development on Reported Claims		$ 26
Cumulative Number of Reported Claims | claim		43,484
Cumulative Paid Claims and Allocated LAE, Net of Reinsurance		$ 141	87
Cumulative Percentage Paid of Incurred Claims and Allocated LAE, Net of Reinsurance	[4]	77.00%
Specialty financial | Accident Year 2017
Claims Development [Line Items]
Incurred Claims and Allocated LAE, Net of Reinsurance		$ 212
Total IBNR Plus Expected Development on Reported Claims		$ 84
Cumulative Number of Reported Claims | claim		36,116
Cumulative Paid Claims and Allocated LAE, Net of Reinsurance		$ 119
Cumulative Percentage Paid of Incurred Claims and Allocated LAE, Net of Reinsurance	[4]	56.10%
Specialty financial | Excludes short-duration insurance contracts detail for accident years not separately presented
Claims Development [Line Items]
Unpaid losses and LAE, net of reinsurance (excluding unallocated LAE)		$ 221
Other specialty
Claims Development [Line Items]
Incurred Claims and Allocated LAE, Net of Reinsurance		495
Cumulative Paid Claims and Allocated LAE, Net of Reinsurance		300
Unpaid losses and LAE — 11th year and prior (excluding unallocated LAE)		83
Unpaid losses and LAE, net of reinsurance (excluding unallocated LAE)		278
Other specialty | Accident Year 2008
Claims Development [Line Items]
Incurred Claims and Allocated LAE, Net of Reinsurance		43	44	45	45	46	48	49	49	49	49
Total IBNR Plus Expected Development on Reported Claims		$ 3
Cumulative Number of Reported Claims | claim	[5]	0
Cumulative Paid Claims and Allocated LAE, Net of Reinsurance		$ 39	38	37	37	37	35	31	23	16	$ 10
Cumulative Percentage Paid of Incurred Claims and Allocated LAE, Net of Reinsurance	[6]	90.70%
Other specialty | Accident Year 2009
Claims Development [Line Items]
Incurred Claims and Allocated LAE, Net of Reinsurance		$ 33	38	36	37	37	40	41	41	41
Total IBNR Plus Expected Development on Reported Claims		$ 7
Cumulative Number of Reported Claims | claim	[5]	0
Cumulative Paid Claims and Allocated LAE, Net of Reinsurance		$ 25	26	24	22	22	19	15	12	$ 8
Cumulative Percentage Paid of Incurred Claims and Allocated LAE, Net of Reinsurance	[6]	75.80%
Other specialty | Accident Year 2010
Claims Development [Line Items]
Incurred Claims and Allocated LAE, Net of Reinsurance		$ 40	40	40	40	39	40	39	36
Total IBNR Plus Expected Development on Reported Claims		$ 2
Cumulative Number of Reported Claims | claim	[5]	0
Cumulative Paid Claims and Allocated LAE, Net of Reinsurance		$ 36	35	33	27	24	21	14	$ 8
Cumulative Percentage Paid of Incurred Claims and Allocated LAE, Net of Reinsurance	[6]	90.00%
Other specialty | Accident Year 2011
Claims Development [Line Items]
Incurred Claims and Allocated LAE, Net of Reinsurance		$ 44	44	43	43	42	43	39
Total IBNR Plus Expected Development on Reported Claims		$ 4
Cumulative Number of Reported Claims | claim	[5]	0
Cumulative Paid Claims and Allocated LAE, Net of Reinsurance		$ 37	36	34	28	25	20	$ 12
Cumulative Percentage Paid of Incurred Claims and Allocated LAE, Net of Reinsurance	[6]	84.10%
Other specialty | Accident Year 2012
Claims Development [Line Items]
Incurred Claims and Allocated LAE, Net of Reinsurance		$ 39	41	40	39	40	42
Total IBNR Plus Expected Development on Reported Claims		$ 8
Cumulative Number of Reported Claims | claim	[5]	0
Cumulative Paid Claims and Allocated LAE, Net of Reinsurance		$ 30	28	25	21	17	$ 8
Cumulative Percentage Paid of Incurred Claims and Allocated LAE, Net of Reinsurance	[6]	76.90%
Other specialty | Accident Year 2013
Claims Development [Line Items]
Incurred Claims and Allocated LAE, Net of Reinsurance		$ 50	47	46	47	46
Total IBNR Plus Expected Development on Reported Claims		$ 5
Cumulative Number of Reported Claims | claim	[5]	0
Cumulative Paid Claims and Allocated LAE, Net of Reinsurance		$ 37	34	22	16	$ 7
Cumulative Percentage Paid of Incurred Claims and Allocated LAE, Net of Reinsurance	[6]	74.00%
Other specialty | Accident Year 2014
Claims Development [Line Items]
Incurred Claims and Allocated LAE, Net of Reinsurance		$ 59	59	57	58
Total IBNR Plus Expected Development on Reported Claims		$ 16
Cumulative Number of Reported Claims | claim	[5]	0
Cumulative Paid Claims and Allocated LAE, Net of Reinsurance		$ 36	30	21	$ 13
Cumulative Percentage Paid of Incurred Claims and Allocated LAE, Net of Reinsurance	[6]	61.00%
Other specialty | Accident Year 2015
Claims Development [Line Items]
Incurred Claims and Allocated LAE, Net of Reinsurance		$ 63	60	59
Total IBNR Plus Expected Development on Reported Claims		$ 20
Cumulative Number of Reported Claims | claim	[5]	0
Cumulative Paid Claims and Allocated LAE, Net of Reinsurance		$ 31	26	$ 10
Cumulative Percentage Paid of Incurred Claims and Allocated LAE, Net of Reinsurance	[6]	49.20%
Other specialty | Accident Year 2016
Claims Development [Line Items]
Incurred Claims and Allocated LAE, Net of Reinsurance		$ 61	61
Total IBNR Plus Expected Development on Reported Claims		$ 31
Cumulative Number of Reported Claims | claim	[5]	0
Cumulative Paid Claims and Allocated LAE, Net of Reinsurance		$ 19	$ 9
Cumulative Percentage Paid of Incurred Claims and Allocated LAE, Net of Reinsurance	[6]	31.10%
Other specialty | Accident Year 2017
Claims Development [Line Items]
Incurred Claims and Allocated LAE, Net of Reinsurance		$ 63
Total IBNR Plus Expected Development on Reported Claims		$ 47
Cumulative Number of Reported Claims | claim	[5]	0
Cumulative Paid Claims and Allocated LAE, Net of Reinsurance		$ 10
Cumulative Percentage Paid of Incurred Claims and Allocated LAE, Net of Reinsurance	[6]	15.90%
Other specialty | Excludes short-duration insurance contracts detail for accident years not separately presented
Claims Development [Line Items]
Unpaid losses and LAE, net of reinsurance (excluding unallocated LAE)		$ 195
[1]	Represents the cumulative percentage paid of incurred claims and allocated LAE (net of reinsurance, as estimated at December 31, 2017).
[2]	Represents the cumulative percentage paid of incurred claims and allocated LAE (net of reinsurance, as estimated at December 31, 2017).
[3]	Represents the cumulative percentage paid of incurred claims and allocated LAE (net of reinsurance, as estimated at December 31, 2017).
[4]	Represents the cumulative percentage paid of incurred claims and allocated LAE (net of reinsurance, as estimated at December 31, 2017).
[5]	The amounts shown in Other specialty represent business assumed by AFG’s internal reinsurance program from the operations that make up AFG’s other Specialty property and casualty insurance sub-segments. Accordingly, the liability for incurred claims and allocated LAE represents additional reserves held on claims counted in the tables provided for the other sub-segments (above).
[6]	Represents the cumulative percentage paid of incurred claims and allocated LAE (net of reinsurance, as estimated at December 31, 2017).

Insurance - Short-duration in97

Insurance - Short-duration insurance contracts, historical claims duration (Details) - Property and casualty insurance	Dec. 31, 2017
Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance [Line Items]
Year 1	32.70%
Year 2	26.10%
Year 3	12.10%
Year 4	8.50%
Year 5	5.30%
Year 6	3.30%
Year 7	1.80%
Year 8	1.20%
Year 9	0.80%
Year 10	1.00%
Year 1, Cumulative	32.70%
Year 2, Cumulative	58.80%
Year 3, Cumulative	70.90%
Year 4, Cumulative	79.40%
Year 5, Cumulative	84.70%
Year 6, Cumulative	88.00%
Year 7, Cumulative	89.80%
Year 8, Cumulative	91.00%
Year 9, Cumulative	91.80%
Year 10, Cumulative	92.80%
Property and transportation
Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance [Line Items]
Year 1	45.90%
Year 2	29.90%
Year 3	8.40%
Year 4	6.30%
Year 5	3.70%
Year 6	1.90%
Year 7	0.90%
Year 8	0.30%
Year 9	0.40%
Year 10	0.10%
Year 1, Cumulative	45.90%
Year 2, Cumulative	75.80%
Year 3, Cumulative	84.20%
Year 4, Cumulative	90.50%
Year 5, Cumulative	94.20%
Year 6, Cumulative	96.10%
Year 7, Cumulative	97.00%
Year 8, Cumulative	97.30%
Year 9, Cumulative	97.70%
Year 10, Cumulative	97.80%
Specialty casualty
Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance [Line Items]
Year 1	18.60%
Year 2	23.40%
Year 3	16.20%
Year 4	11.00%
Year 5	6.90%
Year 6	4.60%
Year 7	2.80%
Year 8	2.10%
Year 9	1.60%
Year 10	1.60%
Year 1, Cumulative	18.60%
Year 2, Cumulative	42.00%
Year 3, Cumulative	58.20%
Year 4, Cumulative	69.20%
Year 5, Cumulative	76.10%
Year 6, Cumulative	80.70%
Year 7, Cumulative	83.50%
Year 8, Cumulative	85.60%
Year 9, Cumulative	87.20%
Year 10, Cumulative	88.80%
Specialty financial
Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance [Line Items]
Year 1	49.80%
Year 2	26.30%
Year 3	8.30%
Year 4	5.70%
Year 5	3.60%
Year 6	2.00%
Year 7	0.20%
Year 8	0.10%
Year 9	0.00%
Year 10	1.50%
Year 1, Cumulative	49.80%
Year 2, Cumulative	76.10%
Year 3, Cumulative	84.40%
Year 4, Cumulative	90.10%
Year 5, Cumulative	93.70%
Year 6, Cumulative	95.70%
Year 7, Cumulative	95.90%
Year 8, Cumulative	96.00%
Year 9, Cumulative	96.00%
Year 10, Cumulative	97.50%
Other specialty
Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance [Line Items]
Year 1	19.80%
Year 2	17.30%
Year 3	12.50%
Year 4	12.80%
Year 5	8.90%
Year 6	5.90%
Year 7	3.30%
Year 8	2.90%
Year 9	(0.40%)
Year 10	2.30%
Year 1, Cumulative	19.80%
Year 2, Cumulative	37.10%
Year 3, Cumulative	49.60%
Year 4, Cumulative	62.40%
Year 5, Cumulative	71.30%
Year 6, Cumulative	77.20%
Year 7, Cumulative	80.50%
Year 8, Cumulative	83.40%
Year 9, Cumulative	83.00%
Year 10, Cumulative	85.30%

Insurance - Net earnings and ca

Insurance - Net earnings and capital and surplus on a statutory basis for the insurance subsidiaries (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Property and casualty companies
Statutory information
Net Earnings	$ 484	$ 461	$ 408
Capital and Surplus	2,729	2,939
Life insurance companies
Statutory information
Net Earnings	286	167	$ 399
Capital and Surplus	$ 2,132	$ 1,976

Insurance - Reinsurance informa

Insurance - Reinsurance information table including assumed, ceded, and recoveries (Details) - Property and casualty insurance - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Effects of Reinsurance [Line Items]
Direct premiums written	$ 6,310	$ 5,858	$ 5,713
Reinsurance assumed	192	123	119
Reinsurance ceded	(1,751)	(1,595)	(1,505)
Net written premiums	4,751	4,386	4,327
Direct premiums earned	6,112	5,745	5,613
Reinsurance assumed	157	118	105
Reinsurance ceded	(1,690)	(1,535)	(1,494)
Net earned premiums	4,579	4,328	4,224
Reinsurance recoveries	$ 1,379	$ 810	$ 936

Insurance - Liabilities for exc

Insurance - Liabilities for excess benefits expected to be paid on future deaths and annuitizations, guaranteed withdrawal benefits and accrued persistency and premium bonuses (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Insurance [Abstract]
Expected death and annuitization	$ 228	$ 223
Guaranteed withdrawal benefits	357	278
Accrued persistency and premium bonuses	$ 3	$ 6

Additional Information - Narrat

Additional Information - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Allowance for reinsurance recoverables [Line Items]
Total rental expense	$ 69	$ 67	$ 70
Operating lease future minimum payments due in next year	63
Operating lease future minimum payments due in year two	57
Operating lease future minimum payments due in year three	50
Operating lease future minimum payments due in year four	42
Operating lease future minimum payments due in year five	34
Operating lease future minimum payments due after year five	100
Commitments to fund limited partnerships	484
Retirement and employee savings plan expense	45	43	34
Allowance for reinsurance recoverables
Allowance for reinsurance recoverables [Line Items]
Aggregate allowance for losses on reinsurance recoverables	20	22
Net expense reduction against the allowance for losses on reinsurance recoverables			$ (3)
Reinsurance recoverable write-offs	2
Maximum | Allowance for reinsurance recoverables
Allowance for reinsurance recoverables [Line Items]
Net expense reduction against the allowance for losses on reinsurance recoverables	$ (1)	$ (1)

Condensed Financial Informat102

Condensed Financial Information of Parent Company - Condensed Balance Sheet (Details) - USD ($) $ in Millions		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Assets:
Cash and cash equivalents		$ 2,338	$ 2,107	$ 1,220	$ 1,343
Other investments		1,311	1,034
Total assets		60,658	55,072	49,837
Liabilities and Equity:
Long-term debt		1,301	1,283
Shareholders’ equity		5,330	4,916
Total liabilities and equity		60,658	55,072
AFG
Assets:
Cash and cash equivalents		299	197	$ 189	$ 292
Investment in securities		70	63
Investment in subsidiaries	[1]	6,310	5,989
Other investments		2	2
Other assets		141	136
Total assets		6,822	6,387
Liabilities and Equity:
Long-term debt		1,301	1,283
Other liabilities		191	188
Shareholders’ equity		5,330	4,916
Total liabilities and equity		$ 6,822	$ 6,387
[1]	Investment in subsidiaries includes intercompany receivables and payables.

Condensed Financial Informat103

Condensed Financial Information of Parent Company - Condensed Statement of Earnings (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenues:
Total revenues	$ 1,808	$ 1,835	$ 1,646	$ 1,576	$ 1,737	$ 1,705	$ 1,581	$ 1,475	$ 6,865	$ 6,498	$ 6,145
Costs and Expenses:
Other expenses									422	353	336
Total costs and expenses									6,141	5,711	5,580
Earnings before income taxes									724	787	565
Provision for income taxes									247	119	195
Net Earnings Attributable to Shareholders	166	$ 11	$ 145	$ 153	385	$ 109	$ 54	$ 101	475	649	352
AFG
Revenues:
Dividends from subsidiaries									681	643	311
Equity in undistributed earnings of subsidiaries									264	286	386
Investment and other income									13	7	4
Total revenues									958	936	701
Costs and Expenses:
Interest charges on intercompany borrowings									9	9	9
Interest charges on other borrowings									85	77	73
Other expenses									142	82	72
Total costs and expenses									236	168	154
Earnings before income taxes									722	768	547
Provision for income taxes	$ (56)				$ (177)				247	119	195
Net Earnings Attributable to Shareholders									$ 475	$ 649	$ 352

Condensed Financial Informat104

Condensed Financial Information of Parent Company - Condensed Statement of Comprehensive Income (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement of Other Comprehensive Income [Abstract]
Net earnings attributable to shareholders	$ 166	$ 11	$ 145	$ 153	$ 385	$ 109	$ 54	$ 101	$ 475	$ 649	$ 352
Comprehensive income (loss) attributable to shareholders									771	711	(71)
AFG
Statement of Other Comprehensive Income [Abstract]
Net earnings attributable to shareholders									475	649	352
Other comprehensive income (loss), net of tax									296	62	(423)
Comprehensive income (loss) attributable to shareholders									$ 771	$ 711	$ (71)

Condensed Financial Informat105

Condensed Financial Information of Parent Company - Condensed Statement of Cash Flows (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Operating Activities:
Net earnings attributable to shareholders	$ 166	$ 11	$ 145	$ 153	$ 385	$ 109	$ 54	$ 101	$ 475	$ 649	$ 352
Adjustments:
Net cash provided by operating activities									1,804	1,150	1,353
Investing Activities:
Net cash used in investing activities									(3,292)	(2,981)	(4,573)
Financing Activities:
Additional long-term borrowings									712	302	145
Reductions of long-term debt									(745)	(18)	(192)
Issuances of Common Stock									37	35	61
Repurchases of Common Stock									0	(133)	(126)
Cash dividends paid on Common Stock									(417)	(185)	(176)
Net cash provided by (used in) financing activities									1,719	2,718	3,097
Net Change in Cash and Cash Equivalents									231	887	(123)
Cash and cash equivalents at beginning of year				2,107				1,220	2,107	1,220	1,343
Cash and cash equivalents at end of year	2,338				2,107				2,338	2,107	1,220
AFG
Operating Activities:
Net earnings attributable to shareholders									475	649	352
Adjustments:
Equity in net earnings of subsidiaries									(575)	(638)	(451)
Dividends from subsidiaries									580	611	280
Other operating activities, net									98	(67)	(19)
Net cash provided by operating activities									578	555	162
Investing Activities:
Capital contributions to subsidiaries									(93)	(560)	(27)
Returns of capital from subsidiaries									30	0	1
Purchases of investments, property and equipment									(2)	(1)	(10)
Proceeds from maturities and redemptions of investments									2	1	0
Proceeds from sales of investments, property and equipment									0	0	3
Net cash used in investing activities									(63)	(560)	(33)
Financing Activities:
Additional long-term borrowings									712	296	145
Reductions of long-term debt									(745)	0	(132)
Issuances of Common Stock									37	35	57
Repurchases of Common Stock									0	(133)	(126)
Cash dividends paid on Common Stock									(417)	(185)	(176)
Net cash provided by (used in) financing activities									(413)	13	(232)
Net Change in Cash and Cash Equivalents									102	8	(103)
Cash and cash equivalents at beginning of year				$ 197				$ 189	197	189	292
Cash and cash equivalents at end of year	$ 299				$ 197				$ 299	$ 197	$ 189

Supplementary Insurance Info106

Supplementary Insurance Information - Table (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Supplementary Insurance Information, by Segment [Line Items]
Deferred policy acquisition costs	$ 1,216	$ 1,239	$ 1,184
Reserves for future policy benefits, claims and unpaid losses and LAE	43,652	39,161	35,454
Unearned premiums	2,410	2,171	2,060
Net earned premiums	4,601	4,352	4,328
Net investment income	1,831	1,696	1,633
Benefits, claims, losses and settlement expenses	3,873	3,595	3,558
Amortization of deferred policy acquisition costs	690	673	653
Other operating expenses	1,578	1,443	1,369
Net written premiums (excluding life)	4,754	4,389	4,400
Property and casualty insurance
Supplementary Insurance Information, by Segment [Line Items]
Deferred policy acquisition costs	270	238	226
Reserves for future policy benefits, claims and unpaid losses and LAE	9,678	8,563	8,127
Unearned premiums	2,410	2,171	2,060
Net earned premiums	4,579	4,328	4,224
Net investment income	362	350	319
Benefits, claims, losses and settlement expenses	2,955	2,762	2,695
Amortization of deferred policy acquisition costs	556	520	511
Other operating expenses	867	870	839
Net written premiums (excluding life)	4,751	4,386	4,327
Annuity
Supplementary Insurance Information, by Segment [Line Items]
Deferred policy acquisition costs	920	981	934
Reserves for future policy benefits, claims and unpaid losses and LAE	33,316	29,907	26,622
Net investment income	1,458	1,356	1,224
Benefits, claims, losses and settlement expenses	892	800	732
Amortization of deferred policy acquisition costs	130	149	136
Other operating expenses	159	142	123
Run-off long-term care and life
Supplementary Insurance Information, by Segment [Line Items]
Deferred policy acquisition costs	26	20	24
Reserves for future policy benefits, claims and unpaid losses and LAE	658	691	705
Net earned premiums	22	24	104
Net investment income	20	21	80
Benefits, claims, losses and settlement expenses	26	33	131
Amortization of deferred policy acquisition costs	4	4	6
Other operating expenses	11	10	37
Net written premiums (excluding life)	3	3	73
Other
Supplementary Insurance Information, by Segment [Line Items]
Net investment income	(9)	(31)	10
Other operating expenses	$ 541	$ 421	$ 370