American Financial (AFG) 10-Q 4 May 18 2018 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2018	May 01, 2018
Document and Entity Information [Abstract]
Entity Registrant Name	AMERICAN FINANCIAL GROUP INC
Entity Central Index Key	1,042,046
Document Type	10-Q
Document Period End Date	Mar. 31, 2018
Amendment Flag	false
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	Q1
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		88,935,221

Consolidated Balance Sheet (Una

Consolidated Balance Sheet (Unaudited) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Assets:
Cash and cash equivalents	$ 1,659	$ 2,338
Investments:
Fixed maturities, available for sale at fair value (amortized cost — $38,383 and $37,038)	39,125	38,379
Fixed maturities, trading at fair value	160	348
Equity securities, at fair value	1,786	1,662
Investments accounted for using the equity method	1,097	999
Mortgage loans	1,082	1,125
Policy loans	181	184
Equity index call options	591	701
Real estate and other investments	268	312
Total cash and investments	45,949	46,048
Recoverables from reinsurers	3,173	3,369
Prepaid reinsurance premiums	614	600
Agents’ balances and premiums receivable	1,113	1,146
Deferred policy acquisition costs	1,417	1,216
Assets of managed investment entities	5,090	4,902
Other receivables	918	1,030
Variable annuity assets (separate accounts)	632	644
Other assets	1,551	1,504
Goodwill	199	199
Total assets	60,656	60,658
Liabilities and Equity:
Unpaid losses and loss adjustment expenses	9,193	9,678
Unearned premiums	2,413	2,410
Annuity benefits accumulated	33,901	33,316
Life, accident and health reserves	656	658
Payable to reinsurers	661	743
Liabilities of managed investment entities	4,869	4,687
Long-term debt	1,301	1,301
Variable annuity liabilities (separate accounts)	632	644
Other liabilities	1,847	1,887
Total liabilities	55,473	55,324
Temporary equity
Redeemable noncontrolling interests	0	3
Shareholders’ equity:
Common Stock, no par value — 200,000,000 shares authorized — 88,881,213 and 88,275,460 shares outstanding	89	88
Capital surplus	1,205	1,181
Retained earnings	3,584	3,248
Accumulated other comprehensive income, net of tax	305	813
Total shareholders’ equity	5,183	5,330
Noncontrolling interests	0	1
Total equity	5,183	5,331
Total liabilities and equity	$ 60,656	$ 60,658

Consolidated Balance Sheet (Un3

Consolidated Balance Sheet (Unaudited) (Parenthetical) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Statement of Financial Position [Abstract]
Fixed maturities, available for sale at amortized cost	$ 38,383	$ 37,038
Common Stock, par value (USD per share)	$ 0	$ 0
Common Stock, shares authorized	200,000,000	200,000,000
Common Stock, shares outstanding	88,881,213	88,275,460

Consolidated Statement of Earni

Consolidated Statement of Earnings (Unaudited) - USD ($) shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Revenues:
Property and casualty insurance net earned premiums	$ 1,107	$ 1,022
Life, accident and health net earned premiums	6	6
Net investment income	495	435
Realized gains (losses) on:
Realized gains (losses) on securities	(93)	3
Income (loss) of managed investment entities:
Investment income	58	51
Gain (loss) on change in fair value of assets/liabilities	(3)	0
Other income	49	59
Total revenues	1,619	1,576
Costs and Expenses:
Property and casualty insurance: Losses and loss adjustment expenses	641	609
Property and casualty insurance: Commissions and other underwriting expenses	381	339
Annuity benefits	182	196
Life, accident and health benefits	11	9
Annuity and supplemental insurance acquisition expenses	82	53
Interest charges on borrowed money	15	21
Expenses of managed investment entities	48	41
Other expenses	85	85
Total costs and expenses	1,445	1,353
Earnings before income taxes	174	223
Provision for income taxes	33	68
Net earnings, including noncontrolling interests	141	155
Less: Net earnings (losses) attributable to noncontrolling interests	(4)	2
Net Earnings Attributable to Shareholders	$ 145	$ 153
Earnings Attributable to Shareholders per Common Share:
Basic (USD per share)	$ 1.64	$ 1.76
Diluted (USD per share)	$ 1.60	$ 1.72
Average number of Common Shares:
Basic (shares)	88.6	87.2
Diluted (shares)	90.4	89.3
Cash dividends per Common Share (USD per share)	$ 0.35	$ 0.3125
Supplemental disclosure of Realized gains on securities:
Realized gains (losses) before impairments	$ (92)	$ 9
Losses on securities with impairment	(1)	(6)
Non-credit portion recognized in other comprehensive income (loss)	0	0
Impairment charges recognized in earnings	(1)	(6)
Total realized gains (losses) on securities	$ (93)	$ 3

Consolidated Statement of Compr

Consolidated Statement of Comprehensive Income (Unaudited) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Statement of Comprehensive Income [Abstract]
Net earnings, including noncontrolling interests	$ 141	$ 155
Net unrealized gains (losses) on securities:
Unrealized holding gains (losses) on securities arising during the period	(279)	125
Reclassification adjustment for realized (gains) losses included in net earnings	2	0
Total net unrealized gains (losses) on securities	(277)	125
Net unrealized losses on cash flow hedges	(11)	(1)
Foreign currency translation adjustments	1	0
Other comprehensive income (loss), net of tax	(287)	124
Total comprehensive income (loss), net of tax	(146)	279
Less: Comprehensive income (loss) attributable to noncontrolling interests	(4)	2
Comprehensive income (loss) attributable to shareholders	$ (142)	$ 277

Consolidated Statement of Chang

Consolidated Statement of Changes in Equity (Unaudited) - USD ($) $ in Millions		Total	Total	Common Shares	Common Stock and Capital Surplus	Retained Earnings	Accumulated Other Comp. Income (Loss)	Noncontrolling interests
Beginning Balance, shares at Dec. 31, 2016				86,924,399
Beginning Balance at Dec. 31, 2016		$ 4,919	$ 4,916		$ 1,198	$ 3,343	$ 375	$ 3
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net earnings (losses) attributable to parent		153	153			153
Net earnings (losses) including portion attributable to nonredeemable noncontrolling interest		155						2
Other comprehensive income (loss)		124	124				124	0
Dividends on Common Stock		(27)	(27)			(27)
Shares issued:
Exercise of stock options, shares				411,167
Exercise of stock options		15	15		15
Restricted stock awards, shares				232,250
Restricted stock awards		0	0		0
Other benefit plans, shares				54,453
Other benefit plans		5	5		5
Dividend reinvestment plan, shares				3,277
Stock-based compensation expense		8	8		8
Shares exchanged — benefit plans, shares				(32,176)
Shares exchanged — benefit plans		(3)	(3)		0	(3)
Forfeitures of restricted stock, shares				(1,699)
Forfeitures of restricted stock		0	0		0
Other		(1)						(1)
Ending Balance, shares at Mar. 31, 2017				87,591,671
Ending Balance at Mar. 31, 2017		5,195	5,191		1,226	3,466	499	4
Beginning Balance, Redeemable Noncontrolling Interests at Dec. 31, 2016		0
Ending Balance, Redeemable Noncontrolling Interests at Mar. 31, 2017		0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect of accounting change	[1]						0
Cumulative effect of accounting change		$ 4	4			225	(221)
Beginning Balance, shares at Dec. 31, 2017		88,275,460		88,275,460
Beginning Balance at Dec. 31, 2017		$ 5,331	5,330		1,269	3,248	813	1
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net earnings (losses) attributable to parent		145	145			145
Net earnings (losses) including portion attributable to nonredeemable noncontrolling interest		144						(1)
Other comprehensive income (loss)		(287)	(287)				(287)	0
Dividends on Common Stock		(31)	(31)			(31)
Shares issued:
Exercise of stock options, shares				374,314
Exercise of stock options		14	14		14
Restricted stock awards, shares				200,625
Restricted stock awards		0	0		0
Other benefit plans, shares				52,583
Other benefit plans		6	6		6
Dividend reinvestment plan, shares				2,779
Dividend reinvestment plan		0	0		0
Stock-based compensation expense		5	5		5
Shares exchanged — benefit plans, shares				(23,882)
Shares exchanged — benefit plans		(3)	(3)		0	(3)
Forfeitures of restricted stock, shares				(666)
Forfeitures of restricted stock		0	0		0
Other		$ 0						0
Ending Balance, shares at Mar. 31, 2018		88,881,213		88,881,213
Ending Balance at Mar. 31, 2018		$ 5,183	$ 5,183		$ 1,294	$ 3,584	$ 305	$ 0
Beginning Balance, Redeemable Noncontrolling Interests at Dec. 31, 2017		3
Redeemable Noncontrolling Interest, Equity, Carrying Amount [Abstract]
Net earnings attributable to redeemable noncontrolling interests		(3)
Ending Balance, Redeemable Noncontrolling Interests at Mar. 31, 2018		$ 0
[1]	On January 1, 2018, AFG adopted new guidance that requires all equity securities other than those accounted for under the equity method to be reported at fair value with holding gains and losses recognized in net earnings. At the date of adoption, the $221 million net unrealized gain on equity securities classified as available for sale (with unrealized holding gains and losses reported in AOCI) under the prior guidance was reclassified from AOCI to retained earnings as the cumulative effect of an accounting change.

Consolidated Statement of Cash

Consolidated Statement of Cash Flows (Unaudited) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Operating Activities:
Net earnings, including noncontrolling interests	$ 141	$ 155
Adjustments:
Depreciation and amortization	71	38
Annuity benefits	182	196
Realized (gains) losses on investing activities	93	(17)
Net sales of trading securities	61	3
Deferred annuity and life policy acquisition costs	(57)	(67)
Change in:
Reinsurance and other receivables	245	63
Other assets	26	(58)
Insurance claims and reserves	(284)	57
Payable to reinsurers	(82)	(13)
Other liabilities	(16)	45
Managed investment entities’ assets/liabilities	31	(487)
Other operating activities, net	(20)	9
Net cash provided by (used in) operating activities	391	(76)
Investing Activities:
Purchases of fixed maturities	(2,464)	(2,879)
Purchases of equity securities	(212)	(22)
Purchases of mortgage loans	0	(23)
Purchases of equity index call options and other investments	(195)	(181)
Purchases of real estate, property and equipment	(23)	(11)
Proceeds from maturities and redemptions of fixed maturities	962	1,511
Proceeds from repayments of mortgage loans	43	12
Proceeds from sales of fixed maturities	105	38
Proceeds from sales of equity securities	32	14
Proceeds from sales and settlements of equity index call options and other investments	208	174
Proceeds from sales of real estate, property and equipment	0	24
Managed investment entities:
Purchases of investments	(606)	(910)
Proceeds from sales and redemptions of investments	478	1,058
Other investing activities, net	16	1
Net cash used in investing activities	(1,656)	(1,194)
Financing Activities:
Annuity receipts	1,148	1,290
Annuity surrenders, benefits and withdrawals	(647)	(567)
Net transfers from variable annuity assets	11	17
Issuances of managed investment entities’ liabilities	775	537
Retirements of managed investment entities’ liabilities	(684)	(212)
Issuances of Common Stock	14	15
Cash dividends paid on Common Stock	(31)	(27)
Other financing activities, net	0	0
Net cash provided by financing activities	586	1,053
Net Change in Cash and Cash Equivalents	(679)	(217)
Cash and cash equivalents at beginning of period	2,338	2,107
Cash and cash equivalents at end of period	$ 1,659	$ 1,890

Accounting Policies

Accounting Policies	3 Months Ended
	Mar. 31, 2018
Accounting Policies [Abstract]
Accounting Policies	Accounting Policies Basis of Presentation The accompanying consolidated financial statements for American Financial Group, Inc. and its subsidiaries (“AFG”) are unaudited; however, management believes that all adjustments (consisting only of normal recurring accruals unless otherwise disclosed herein) necessary for fair presentation have been made. The results of operations for interim periods are not necessarily indicative of results to be expected for the year. The financial statements have been prepared in accordance with the instructions to Form 10-Q and, therefore, do not include all information and footnotes necessary to be in conformity with U.S. generally accepted accounting principles (“GAAP”). Certain reclassifications have been made to prior periods 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 March 31, 2018 , and prior to the filing of this Form 10-Q, have been evaluated for potential recognition or disclosure herein. The preparation of the financial statements 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 in the first three months of 2018 . Investments On January 1, 2018, AFG adopted Accounting Standards Update (“ASU”) 2016-01, which requires all equity securities other than those accounted for under the equity method to be reported at fair value with holding gains and losses recognized in net earnings. At December 31, 2017, AFG had $1.60 billion in equity securities classified as “available for sale” under the prior guidance with holding gains and losses included in accumulated other comprehensive income (“AOCI”) instead of net earnings. At the date of adoption, the $221 million net unrealized gain on equity securities included in AOCI was reclassified to retained earnings as the cumulative effect of an accounting change. The cumulative effect of the accounting change also includes the net unrealized gain on AFG’s small number of limited partnerships and similar investments carried at cost under the prior guidance that are carried at fair value through net earnings under the new guidance ( $4 million net of tax at the date of adoption). Holding gains and losses on equity securities carried at fair value under ASU 2016-01 are generally recorded in realized gains (losses) on securities. However, prior to the adoption of the new guidance, AFG classified a small portion of its equity securities as “trading” and reported those investments at fair value with holding gains and losses recognized in net investment income. These investments consisted primarily of equity securities held to offset the impact of changes in the stock market on employee benefit plans that are impacted by stock market performance and totaled $62 million at December 31, 2017. Following the adoption of the new guidance, AFG continues to record holding gains and losses on these securities, as well as its small portfolio of limited partnerships and similar investments carried at fair value under the new guidance and certain other securities classified at purchase as “fair value through net investment income” in net investment income. Under the new guidance, AFG recorded a net realized loss of $94 million on equity securities during the first three months of 2018 on securities that were still owned at March 31, 2018 . Under the prior guidance, this holding loss would have been recorded in AOCI (with the exception of any impairment charge that may have been recorded). Because almost all of the equity securities impacted by the new guidance were carried at fair value through AOCI under the prior guidance, the adoption of the new guidance did not have a material impact on AFG’s financial position. Fixed maturity 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 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. 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. Limited partnerships and similar investments are generally accounted for using the equity method of accounting. Under the equity method, AFG records its share of the earnings or losses of the investee based on when they are reported by the investee in its financial statements rather than in the period in which the investee declares a dividend. AFG’s share of the earnings or losses from equity method investments is generally recorded on a quarter lag due to the timing of the receipt of the investee’s financial statements. AFG’s equity in the earnings (losses) of limited partnerships and similar investments is included in net investment income. Gains or losses on fixed maturity 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 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 G — “ 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. 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. 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 annuity policy charges are recorded in 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 presented in its Balance Sheet as a direct reduction in the carrying value of long-term debt and are amortized over the life of the related debt using the effective interest method as a component of interest expense. Debt issuance costs related to AFG’s revolving credit facilities are included in other assets in AFG’s Balance Sheet. 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. 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. 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. 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. AFG records excess tax benefits or deficiencies for share-based payments through income tax expense in the statement of earnings. In addition, AFG accounts for forfeitures of awards when they occur. 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: first three months of 2018 and 2017 — 1.8 million and 2.1 million , respectively. There were no anti-dilutive potential common shares in the first three months of 2018 or 2017 . 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. Revenue Recognition Guidance Effective in 2018 On January 1, 2018, AFG adopted ASU 2014-09, which provides guidance on recognizing revenue when (or as) performance obligations under the contract are satisfied. The new guidance also updates the accounting for certain costs associated with obtaining and fulfilling contracts with customers and requires certain new disclosures. Because revenue recognition for insurance contracts and financial instruments (AFG’s primary sources of revenue) were excluded from the scope of the new guidance, the adoption of ASU 2014-09 did not have a material impact on AFG’s results of operations or financial position.

Segments of Operations

Segments of Operations	3 Months Ended
	Mar. 31, 2018
Segment Reporting [Abstract]
Segments of Operations	Segments of Operations AFG manages its business as three segments: (i) Property and casualty insurance, (ii) Annuity and (iii) Other, which includes holding company costs, revenues and costs of AFG’s limited insurance operations outside of property and casualty insurance and annuities, 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 equipment leasing and 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. Effective January 1, 2018, the results of AFG’s run-off long-term care and life businesses are included in the “Other” segment instead of as a separate reportable segment based on the immaterial size of the remaining operations. Prior period amounts were reclassified for consistent presentation. The following tables (in millions) show AFG’s revenues and earnings before income taxes by segment and sub-segment. Three months ended March 31, 2018 2017 Revenues Property and casualty insurance: Premiums earned: Specialty Property and transportation $ 350 $ 342 Specialty casualty 579 508 Specialty financial 149 147 Other specialty 29 25 Total premiums earned 1,107 1,022 Net investment income 100 86 Other income (a) 2 16 Total property and casualty insurance 1,209 1,124 Annuity: Net investment income 394 347 Other income 26 27 Total annuity 420 374 Other 83 75 Total revenues before realized gains (losses) 1,712 1,573 Realized gains (losses) on securities (93 ) 3 Total revenues $ 1,619 $ 1,576 Earnings Before Income Taxes Property and casualty insurance: Underwriting: Specialty Property and transportation $ 33 $ 43 Specialty casualty 41 15 Specialty financial 15 22 Other specialty 3 (1 ) Other lines (b) (1 ) (1 ) Total underwriting 91 78 Investment and other income, net (a) 93 93 Total property and casualty insurance 184 171 Annuity 125 96 Other (b) (42 ) (47 ) Total earnings before realized gains (losses) and income taxes 267 220 Realized gains (losses) on securities (93 ) 3 Total earnings before income taxes $ 174 $ 223 (a) Includes income of $13 million (before noncontrolling interest) from the sale of a hotel in the first quarter of 2017. (b) Includes holding company interest and expenses.

Fair Value Measurements

Fair Value Measurements	3 Months Ended
	Mar. 31, 2018
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, 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 (“ABS”), mortgage-backed securities (“MBS”), non-affiliated common stocks, equity index call options 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 March 31, 2018 Assets: Available for sale (“AFS”) fixed maturities: U.S. Government and government agencies $ 147 $ 95 $ 8 $ 250 States, municipalities and political subdivisions — 6,941 62 7,003 Foreign government — 132 — 132 Residential MBS — 2,948 115 3,063 Commercial MBS — 893 47 940 Asset-backed securities — 7,751 912 8,663 Corporate and other 30 17,806 1,238 19,074 Total AFS fixed maturities 177 36,566 2,382 39,125 Trading fixed maturities 48 112 — 160 Equity securities 1,500 92 194 1,786 Equity index call options — 591 — 591 Assets of managed investment entities (“MIE”) 301 4,765 24 5,090 Variable annuity assets (separate accounts) (*) — 632 — 632 Total assets accounted for at fair value $ 2,026 $ 42,758 $ 2,600 $ 47,384 Liabilities: Liabilities of managed investment entities $ 287 $ 4,559 $ 23 $ 4,869 Derivatives in annuity benefits accumulated — — 2,549 2,549 Other liabilities — derivatives — 64 — 64 Total liabilities accounted for at fair value $ 287 $ 4,623 $ 2,572 $ 7,482 December 31, 2017 Assets: Available for sale 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 — 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 1,411 86 165 1,662 Equity index call options — 701 — 701 Assets of managed investment entities 307 4,572 23 4,902 Variable annuity assets (separate accounts) (*) — 644 — 644 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 (*) Variable annuity liabilities equal the fair value of variable annuity assets. During the first three months of 2018 and 2017 , there were no transfers between Level 1 and Level 2. Approximately 6% of the total assets carried at fair value at March 31, 2018 , were Level 3 assets. Approximately 78% ( $2.03 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 approximately 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 $2.55 billion at March 31, 2018 . The following table presents information about the unobservable inputs used by management in determining fair value of these embedded derivatives. See Note E — “ Derivatives .” Unobservable Input Range Adjustment for insurance subsidiary’s credit risk 0.1% – 1.7% 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% – 9% 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 the first three months of 2018 and 2017 are presented below (in millions). The transfers into and out of Level 3 were due to changes in the availability of market observable inputs and $29 million of equity securities transferred into Level 3 in the first quarter of 2018 related to a small number of limited partnerships and similar investments carried at cost under the prior guidance that are carried at fair value through net earnings under new guidance adopted on January 1, 2018, as discussed in Note A — “ Accounting Policies — Investments .” 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, 2017 Net Other comprehensive income (loss) Purchases and issuances Sales and settlements Transfer into Level 3 Transfer out of Level 3 Balance at March 31, 2018 AFS fixed maturities: U.S. government agency $ 8 $ — $ — $ — $ — $ — $ — $ 8 State and municipal 148 — (1 ) — (1 ) — (84 ) 62 Residential MBS 122 (4 ) — — (6 ) 7 (4 ) 115 Commercial MBS 36 (1 ) — 12 — — — 47 Asset-backed securities 744 (2 ) 3 204 (37 ) — — 912 Corporate and other 1,044 1 (14 ) 238 (31 ) — — 1,238 Total AFS fixed maturities 2,102 (6 ) (12 ) 454 (75 ) 7 (88 ) 2,382 Equity securities 165 (5 ) — 9 (4 ) 29 — 194 Assets of MIE 23 (2 ) — 3 — — — 24 Total Level 3 assets $ 2,290 $ (13 ) $ (12 ) $ 466 $ (79 ) $ 36 $ (88 ) $ 2,600 Embedded derivatives $ (2,542 ) $ 63 $ — $ (103 ) $ 33 $ — $ — $ (2,549 ) Total Level 3 liabilities (*) $ (2,542 ) $ 63 $ — $ (103 ) $ 33 $ — $ — $ (2,549 ) Total realized/unrealized gains (losses) included in Balance at December 31, 2016 Net Other comprehensive income (loss) Purchases and issuances Sales and settlements Transfer into Level 3 Transfer out of Level 3 Balance at March 31, 2017 AFS fixed maturities: U.S. government agency $ 8 $ — $ — $ — $ — $ — $ — $ 8 State and municipal 140 — 3 — — — — 143 Residential MBS 190 1 — 1 (8 ) 7 (16 ) 175 Commercial MBS 25 — — — — 4 — 29 Asset-backed securities 484 — — 104 (11 ) 17 — 594 Corporate and other 712 1 4 120 (38 ) 29 — 828 Total AFS fixed maturities 1,559 2 7 225 (57 ) 57 (16 ) 1,777 Equity securities 174 (6 ) 7 12 — — (14 ) 173 Assets of MIE 29 (1 ) — 2 — — (4 ) 26 Total Level 3 assets $ 1,762 $ (5 ) $ 14 $ 239 $ (57 ) $ 57 $ (34 ) $ 1,976 Embedded derivatives $ (1,759 ) $ (147 ) $ — $ (79 ) $ 22 $ — $ — $ (1,963 ) Total Level 3 liabilities (*) $ (1,759 ) $ (147 ) $ — $ (79 ) $ 22 $ — $ — $ (1,963 ) (*) 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. 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 are summarized below (in millions): Carrying Fair Value Value Total Level 1 Level 2 Level 3 March 31, 2018 Financial assets: Cash and cash equivalents $ 1,659 $ 1,659 $ 1,659 $ — $ — Mortgage loans 1,082 1,068 — — 1,068 Policy loans 181 181 — — 181 Total financial assets not accounted for at fair value $ 2,922 $ 2,908 $ 1,659 $ — $ 1,249 Financial liabilities: Annuity benefits accumulated (*) $ 33,692 $ 31,983 $ — $ — $ 31,983 Long-term debt 1,301 1,319 — 1,316 3 Total financial liabilities not accounted for at fair value $ 34,993 $ 33,302 $ — $ 1,316 $ 31,986 December 31, 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 (*) Excludes $209 million and $206 million of life contingent annuities in the payout phase at March 31, 2018 and December 31, 2017 , 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	3 Months Ended
	Mar. 31, 2018
Investments, Debt and Equity Securities [Abstract]
Investments	Investments Available for sale fixed maturities at March 31, 2018 and December 31, 2017 , consisted of the following (in millions): March 31, 2018 December 31, 2017 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 $ 253 $ 1 $ (4 ) $ (3 ) $ 250 $ 244 $ 1 $ (3 ) $ (2 ) $ 242 States, municipalities and political subdivisions 6,855 187 (39 ) 148 7,003 6,887 254 (18 ) 236 7,123 Foreign government 130 2 — 2 132 124 3 — 3 127 Residential MBS 2,732 338 (7 ) 331 3,063 2,884 349 (6 ) 343 3,227 Commercial MBS 922 21 (3 ) 18 940 927 36 (1 ) 35 962 Asset-backed securities 8,546 148 (31 ) 117 8,663 7,836 142 (16 ) 126 7,962 Corporate and other 18,945 308 (179 ) 129 19,074 18,136 638 (38 ) 600 18,736 Total fixed maturities $ 38,383 $ 1,005 $ (263 ) $ 742 $ 39,125 $ 37,038 $ 1,423 $ (82 ) $ 1,341 $ 38,379 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 March 31, 2018 and December 31, 2017 were $155 million and $158 million , respectively. Gross unrealized gains on such securities at March 31, 2018 and December 31, 2017 were $136 million and $137 million , respectively. Gross unrealized losses on such securities at March 31, 2018 and December 31, 2017 were $4 million . 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. As discussed in Note A — “ Accounting Policies — Investments ,” beginning on January 1, 2018, AFG implemented new accounting guidance, which required all equity securities previously classified as “available for sale” to be reported at fair value, with holding gains and losses recognized in net earnings. Equity securities reported at fair value consisted of the following at March 31, 2018 (in millions): Fair Value in Actual Cost Fair Value excess of Cost Common stocks $ 1,099 $ 1,154 $ 55 Perpetual preferred stocks 632 632 — Total equity securities carried at fair value $ 1,731 $ 1,786 $ 55 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 the following balance sheet dates. 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 March 31, 2018 Fixed maturities: U.S. Government and government agencies $ (1 ) $ 57 98 % $ (3 ) $ 119 98 % States, municipalities and political subdivisions (26 ) 1,745 99 % (13 ) 411 97 % Foreign government — 22 100 % — — — % Residential MBS (3 ) 155 98 % (4 ) 114 97 % Commercial MBS (3 ) 148 98 % — — — % Asset-backed securities (21 ) 2,586 99 % (10 ) 306 97 % Corporate and other (149 ) 7,352 98 % (30 ) 601 95 % Total fixed maturities $ (203 ) $ 12,065 98 % $ (60 ) $ 1,551 96 % December 31, 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 % At March 31, 2018 , the gross unrealized losses on fixed maturities of $263 million relate to 1,621 securities. Investment grade securities (as determined by nationally recognized rating agencies) represented approximately 90% of the gross unrealized loss and 94% of the 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. In the first three months of 2018 , AFG recorded less than $1 million in other-than-temporary impairment charges related to its residential MBS. In the first three months of 2018 , AFG recorded $1 million in other-than-temporary impairment charges related to corporate bonds and other fixed maturities. 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 March 31, 2018 . As discussed in Note A — “ Accounting Policies — Investments ,” effective January 1, 2018, all equity securities previously classified as “available for sale” are required to be carried at fair value through net earnings instead of accumulated other comprehensive income and therefore are no longer 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): 2018 2017 Balance at January 1 $ 145 $ 153 Additional credit impairments on: Previously impaired securities — — Securities without prior impairments — — Reductions due to sales or redemptions (1 ) (7 ) Balance at March 31 $ 144 $ 146 The table below sets forth the scheduled maturities of available for sale fixed maturities as of March 31, 2018 (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 $ 793 $ 804 2 % After one year through five years 7,314 7,431 19 % After five years through ten years 13,345 13,425 35 % After ten years 4,731 4,799 12 % 26,183 26,459 68 % ABS (average life of approximately 4-1/2 years) 8,546 8,663 22 % MBS (average life of approximately 4-1/2 years) 3,654 4,003 10 % Total $ 38,383 $ 39,125 100 % 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 March 31, 2018 or December 31, 2017 . 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 March 31, 2018 Net unrealized gain on: Fixed maturities — annuity segment (a) $ 594 $ (125 ) $ 469 Fixed maturities — all other 148 (31 ) 117 Total fixed maturities 742 (156 ) 586 Deferred policy acquisition costs — annuity segment (236 ) 49 (187 ) Annuity benefits accumulated (79 ) 17 (62 ) Unearned revenue 6 (1 ) 5 Total net unrealized gain on marketable securities $ 433 $ (91 ) $ 342 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 (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 other than those accounted for under the equity method are carried at fair value through net earnings. Net Investment Income The following table shows (in millions) investment income earned and investment expenses incurred. Three months ended March 31, 2018 2017 Investment income: Fixed maturities $ 412 $ 389 Equity securities 19 21 Equity in earnings of partnerships and similar investments 46 10 Other 23 20 Gross investment income 500 440 Investment expenses (5 ) (5 ) Net investment income $ 495 $ 435 Realized gains (losses) and changes in unrealized appreciation (depreciation) related to fixed maturity and equity security investments are summarized as follows (in millions): Three months ended March 31, 2018 Three months ended March 31, 2017 Realized gains (losses) Realized gains (losses) Before Impairments Impairments Total Change in Unrealized Before Impairments Impairments Total Change in Unrealized Fixed maturities $ (1 ) $ (1 ) $ (2 ) $ (599 ) $ 5 $ — $ 5 $ 202 Equity securities (a) (95 ) — (95 ) — 2 (9 ) (7 ) 72 Mortgage loans and other investments — — — — 3 — 3 — Other (b) 4 — 4 248 (1 ) 3 2 (83 ) Total pretax (92 ) (1 ) (93 ) (351 ) 9 (6 ) 3 191 Tax effects 20 — 20 74 (3 ) 2 (1 ) (66 ) Net of tax $ (72 ) $ (1 ) $ (73 ) $ (277 ) $ 6 $ (4 ) $ 2 $ 125 (a) As discussed in Note A — “ Accounting Policies — Investments ,” effective January 1, 2018, all equity securities other than those accounted for under the equity method are carried at fair value through net earnings. AFG recorded a net realized loss of $94 million on equity securities during the first three months of 2018 on securities that were still owned at March 31, 2018 . (b) 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 investment transactions consisted of the following (in millions): Three months ended March 31, 2018 2017 Fixed maturities: Gross gains $ 6 $ 5 Gross losses (3 ) — In the first three months of 2017, AFG recorded gross gains of $4 million and gross losses of $2 million on available for sale equity securities.

Derivatives

Derivatives	3 Months Ended
	Mar. 31, 2018
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): March 31, 2018 December 31, 2017 Derivative Balance Sheet Line Asset Liability Asset Liability MBS with embedded derivatives Fixed maturities $ 111 $ — $ 105 $ — Public company warrants Equity securities 3 — 4 — Fixed-indexed annuities (embedded derivative) Annuity benefits accumulated — 2,549 — 2,542 Equity index call options Equity index call options 591 — 701 — Reinsurance contracts (embedded derivative) Other liabilities — 3 — 4 $ 705 $ 2,552 $ 810 $ 2,546 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 counterparties to support its purchased call option assets. This collateral ( $356 million at March 31, 2018 and $389 million at December 31, 2017 ) 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 the first three months of 2018 and 2017 (in millions): Three months ended March 31, Derivative Statement of Earnings Line 2018 2017 MBS with embedded derivatives Realized gains on securities $ (4 ) $ — Public company warrants Realized gains on securities (1 ) — Fixed-indexed annuities (embedded derivative) Annuity benefits 63 (147 ) Equity index call options Annuity benefits (38 ) 141 Reinsurance contract (embedded derivative) Net investment income 1 (1 ) $ 21 $ (7 ) Derivatives Designated and Qualifying as Cash Flow Hedges As of March 31, 2018 , AFG has entered into eleven 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 was $1.68 billion at March 31, 2018 compared to $1.58 billion at December 31, 2017 , reflecting a new swap with an aggregate notional amount at issuance of $130 million entered into in the first quarter of 2018 , 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 zero at March 31, 2018 and less than $1 million December 31, 2017 . The fair value of the effective portion of the interest rate swaps in a liability position and included in other liabilities was $61 million at March 31, 2018 and $31 million at December 31, 2017 . 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 $1 million and $2 million during the first three months of 2018 and 2017 , respectively. There was no ineffectiveness recorded in net earnings during these periods. A collateral receivable supporting these swaps of $107 million at March 31, 2018 and $70 million at December 31, 2017 is included in other assets in AFG’s Balance Sheet.

Deferred Policy Acquisition Cos

Deferred Policy Acquisition Costs	3 Months Ended
	Mar. 31, 2018
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 Other Deferred Deferred Sales Consolidated Costs Costs Inducements PVFP Subtotal Unrealized (*) Total Total Balance at December 31, 2017 $ 270 $ 1,217 $ 102 $ 49 $ 1,368 $ (422 ) $ 946 $ 1,216 Additions 162 57 — — 57 — 57 219 Amortization: Periodic amortization (154 ) (69 ) (5 ) (2 ) (76 ) — (76 ) (230 ) Included in realized gains — 3 — — 3 — 3 3 Foreign currency translation 1 — — — — — — 1 Change in unrealized — — — — — 208 208 208 Balance at March 31, 2018 $ 279 $ 1,208 $ 97 $ 47 $ 1,352 $ (214 ) $ 1,138 $ 1,417 Balance at December 31, 2016 $ 238 $ 1,110 $ 110 $ 46 $ 1,266 $ (265 ) $ 1,001 $ 1,239 Additions 139 67 1 — 68 — 68 207 Amortization: Periodic amortization (135 ) (42 ) (6 ) (2 ) (50 ) — (50 ) (185 ) Included in realized gains — 2 — — 2 — 2 2 Foreign currency translation 1 — — — — — — 1 Change in unrealized — — — — — (59 ) (59 ) (59 ) Balance at March 31, 2017 $ 243 $ 1,137 $ 105 $ 44 $ 1,286 $ (324 ) $ 962 $ 1,205 (*) 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 $143 million and $141 million of accumulated amortization at March 31, 2018 and December 31, 2017 , respectively.

Managed Investment Entities

Managed Investment Entities	3 Months Ended
	Mar. 31, 2018
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 sixteen 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 2018, 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 $221 million (including $136 million invested in the most subordinate tranches) at March 31, 2018 , and $215 million at December 31, 2017 . In March 2018 and March 2017, AFG formed new CLOs, which issued $463 million and $408 million face amount of liabilities, respectively (including $31 million and $24 million face amount purchased by subsidiaries of AFG). During the first three months of 2018 and 2017 , AFG subsidiaries received $17 million and $4 million , respectively, in sale and redemption proceeds from its CLO investments. During the first three months of 2018 , one AFG CLO was substantially liquidated, as permitted by the CLO indenture. 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): Three months ended March 31, 2018 2017 Investment in CLO tranches at end of period $ 221 $ 230 Gains (losses) on change in fair value of assets/liabilities (a): Assets 14 5 Liabilities (17 ) (5 ) Management fees paid to AFG 4 4 CLO earnings (losses) attributable to AFG shareholders (b) 3 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 $38 million and $55 million at March 31, 2018 and December 31, 2017 , respectively. The aggregate unpaid principal balance of the CLOs’ debt exceeded its carrying value by $143 million and $118 million at those dates. The CLO assets include loans with an aggregate fair value of $1 million at both March 31, 2018 and December 31, 2017 , for which the CLOs are not accruing interest because the loans are in default (aggregate unpaid principal balance of $8 million at both those dates).

Goodwill and Other Intangibles

Goodwill and Other Intangibles	3 Months Ended
	Mar. 31, 2018
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill and Other Intangibles	Goodwill and Other Intangibles There were no changes in the goodwill balance of $199 million during the first three months of 2018 . Included in other assets in AFG’s Balance Sheet is $36 million at March 31, 2018 and $26 million at December 31, 2017 in amortizable intangible assets related to property and casualty insurance acquisitions. These amounts are net of accumulated amortization of $32 million and $30 million , respectively. Amortization of intangibles was $2 million in both the first three months of 2018 and 2017 .

Long-Term Debt

Long-Term Debt	3 Months Ended
	Mar. 31, 2018
Debt Disclosure [Abstract]
Long-Term Debt	Long-Term Debt Long-term debt consisted of the following (in millions): March 31, 2018 December 31, 2017 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 $ 590 $ (2 ) $ 588 3.50% Senior Notes due August 2026 425 (5 ) 420 425 (5 ) 420 Other 3 — 3 3 — 3 1,018 (7 ) 1,011 1,018 (7 ) 1,011 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 $ 1,318 $ (17 ) $ 1,301 AFG has no scheduled principal payments on its long-term debt for the balance of 2018 or in the subsequent five years. 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 March 31, 2018 or December 31, 2017 .

Redeemable Noncontrolling Inter

Redeemable Noncontrolling Interests	3 Months Ended
	Mar. 31, 2018
Noncontrolling Interest [Abstract]
Redeemable Noncontrolling Interests	Redeemable Noncontrolling Interests 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. This noncontrolling interest is redeemable at the option of the holder and is presented separately in the mezzanine section of the balance sheet, as discussed in Note A — “ Accounting Policies — Noncontrolling Interests .”

Shareholders' Equity

Shareholders' Equity	3 Months Ended
	Mar. 31, 2018
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. 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 (Loss) AOCI Beginning Balance Pretax Tax Net of tax Attributable to noncontrolling interests Attributable to shareholders Other (c) AOCI Ending Balance Three months ended March 31, 2018 Net unrealized gains (losses) on securities: Unrealized holding losses on securities arising during the period $ (353 ) $ 74 $ (279 ) $ — $ (279 ) Reclassification adjustment for realized (gains) losses included in net earnings (a) 2 — 2 — 2 Total net unrealized gains (losses) on securities (b) $ 840 (351 ) 74 (277 ) — (277 ) $ (221 ) $ 342 Net unrealized losses on cash flow hedges (13 ) (14 ) 3 (11 ) — (11 ) — (24 ) Foreign currency translation adjustments (6 ) 2 (1 ) 1 — 1 — (5 ) Pension and other postretirement plans adjustments (8 ) — — — — — — (8 ) Total $ 813 $ (363 ) $ 76 $ (287 ) $ — $ (287 ) $ (221 ) $ 305 Three months ended March 31, 2017 Net unrealized gains on securities: Unrealized holding gains on securities arising during the period $ 191 $ (66 ) $ 125 $ — $ 125 Reclassification adjustment for realized (gains) losses included in net earnings (a) — — — — — Total net unrealized gains on securities $ 404 191 (66 ) 125 — 125 $ — $ 529 Net unrealized losses on cash flow hedges (7 ) (2 ) 1 (1 ) — (1 ) — (8 ) Foreign currency translation adjustments (15 ) — — — — — — (15 ) Pension and other postretirement plans adjustments (7 ) — — — — — — (7 ) Total $ 375 $ 189 $ (65 ) $ 124 $ — $ 124 $ — $ 499 (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 (b) Includes net unrealized gains of $68 million at both March 31, 2018 and December 31, 2017 related to securities for which only the credit portion of an other-than-temporary impairment has been recorded in earnings. (c) On January 1, 2018, AFG adopted new guidance that requires all equity securities other than those accounted for under the equity method to be reported at fair value with holding gains and losses recognized in net earnings. At the date of adoption, the $221 million net unrealized gain on equity securities classified as available for sale (with unrealized holding gains and losses reported in AOCI) under the prior guidance was reclassified from AOCI to retained earnings as the cumulative effect of an accounting change. 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. In the first three months of 2018 , AFG issued 200,625 shares of restricted Common Stock (fair value of $112.86 per share) under the Stock Incentive Plan. In addition, AFG issued 45,804 shares of Common Stock (fair value of $115.49 per share) in the first quarter of 2018 under the Equity Bonus Plan. AFG did not grant any stock options in the first three months of 2018 . Total compensation expense related to stock incentive plans of AFG and its subsidiaries was $5 million and $11 million in the first three months of 2018 and 2017 , respectively.

Income Taxes

Income Taxes	3 Months Ended
	Mar. 31, 2018
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes The following is a reconciliation of income taxes at the statutory rate ( 21% in 2018 and 35% in 2017 ) to the provision for income taxes as shown in AFG’s Statement of Earnings (dollars in millions): Three months ended March 31, 2018 2017 Amount % of EBT Amount % of EBT Earnings before income taxes (“EBT”) $ 174 $ 223 Income taxes at statutory rate $ 37 21 % $ 78 35 % Effect of: Stock-based compensation (5 ) (3 %) (6 ) (3 %) Tax exempt interest (3 ) (2 %) (6 ) (3 %) Dividends received deduction (1 ) — % (2 ) (1 %) Foreign operations 3 2 % 6 3 % Nondeductible expenses 2 1 % 2 1 % Change in valuation allowance — — % (2 ) (1 %) Other — — % (2 ) (1 %) Provision for income taxes as shown in the statement of earnings $ 33 19 % $ 68 30 % The Tax Cuts and Jobs Act of 2017 (“TCJA”), which was enacted on December 22, 2017, lowered the U.S corporate tax rate to 21% and made other widespread changes to the U.S. tax code effective in 2018. 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 (none through March 31, 2018) will be recorded in the period in which the guidance is published. The favorable impact of stock-based compensation on AFG’s effective tax rate in the first three months of 2018 and 2017 reflects the high volume of employee stock option exercises during that period and the increase in the market price of AFG Common Stock. Approximately $19 million of AFG’s net operating loss carryforwards (“NOL”) subject to separate return limitation year (“SRLY”) tax rules will expire unutilized at December 31, 2018 . Since AFG maintains a full valuation allowance against its SRLY NOLs, the expiration of these loss carryforwards will be offset by a corresponding reduction in the valuation allowance and will have no overall impact on AFG’s income tax expense or results of operations.

Contingencies

Contingencies	3 Months Ended
	Mar. 31, 2018
Commitments and Contingencies Disclosure [Abstract]
Contingencies	Contingencies There have been no significant changes to the matters discussed and referred to in Note M — “Contingencies” of AFG’s 2017 Form 10-K, which covers property and casualty insurance reserves for claims related to environmental exposures, asbestos and other mass tort claims and environmental and occupational injury and disease claims of former subsidiary railroad and manufacturing operations, as well as contingencies related to the sale of substantially all of AFG’s run-off long-term care insurance business.

Insurance

Insurance	3 Months Ended
	Mar. 31, 2018
Insurance [Abstract]
Insurance	Insurance Property and Casualty Insurance Reserves The following table provides an analysis of changes in the liability for losses and loss adjustment expenses during the first three months of 2018 and 2017 (in millions): Three months ended March 31, 2018 2017 Balance at beginning of year $ 9,678 $ 8,563 Less reinsurance recoverables, net of allowance 2,957 2,302 Net liability at beginning of year 6,721 6,261 Provision for losses and LAE occurring in the current period 697 637 Net decrease in the provision for claims of prior years (56 ) (28 ) Total losses and LAE incurred 641 609 Payments for losses and LAE of: Current year (86 ) (84 ) Prior years (554 ) (470 ) Total payments (640 ) (554 ) Reserves of business disposed (*) (319 ) — Foreign currency translation and other 2 8 Net liability at end of period 6,405 6,324 Add back reinsurance recoverables, net of allowance 2,788 2,297 Gross unpaid losses and LAE included in the balance sheet at end of period $ 9,193 $ 8,621 (*) Reflects the reinsurance to close transaction at Neon discussed below. The net decrease in the provision for claims of prior years during the first three months of 2018 reflects (i) lower than expected losses in the crop business (within the Property and transportation sub-segment), (ii) lower than anticipated claim frequency and severity in workers’ compensation business and lower than expected claim severity in the executive liability business (all within the Specialty casualty sub-segment), and (iii) lower than expected claim frequency and severity in the surety business (within the Specialty financial sub-segment). This favorable development was partially offset by higher than expected claim severity and frequency in the targeted markets businesses (within the Specialty casualty sub-segment). The net decrease in the provision for claims of prior years during the first three months of 2017 reflects (i) lower than expected losses in the crop and equine operations and lower than expected claim severity in the property and inland marine business (all within the Property and transportation sub-segment), (ii) lower than anticipated claim severity and frequency in the workers’ compensation businesses and lower than anticipated claim severity at Neon (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 (all within the Specialty financial sub-segment). This favorable development was partially offset by (i) higher than expected claim severity in the ocean marine business (within the Property and transportation sub-segment), (ii) higher than anticipated claim severity in the targeted markets businesses and higher than expected claim severity and frequency in the excess and surplus lines business (all within the Specialty casualty sub-segment) and (iii) an adjustment 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). 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 was effective as of December 31, 2017 (the transaction settled in early 2018). 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 provided Neon with finality on its legacy business.

Accounting Policies (Policies)

Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 2018
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The accompanying consolidated financial statements for American Financial Group, Inc. and its subsidiaries (“AFG”) are unaudited; however, management believes that all adjustments (consisting only of normal recurring accruals unless otherwise disclosed herein) necessary for fair presentation have been made. The results of operations for interim periods are not necessarily indicative of results to be expected for the year. The financial statements have been prepared in accordance with the instructions to Form 10-Q and, therefore, do not include all information and footnotes necessary to be in conformity with U.S. generally accepted accounting principles (“GAAP”). Certain reclassifications have been made to prior periods 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 March 31, 2018 , and prior to the filing of this Form 10-Q, have been evaluated for potential recognition or disclosure herein. The preparation of the financial statements 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 in the first three months of 2018 .
Investments	Investments On January 1, 2018, AFG adopted Accounting Standards Update (“ASU”) 2016-01, which requires all equity securities other than those accounted for under the equity method to be reported at fair value with holding gains and losses recognized in net earnings. At December 31, 2017, AFG had $1.60 billion in equity securities classified as “available for sale” under the prior guidance with holding gains and losses included in accumulated other comprehensive income (“AOCI”) instead of net earnings. At the date of adoption, the $221 million net unrealized gain on equity securities included in AOCI was reclassified to retained earnings as the cumulative effect of an accounting change. The cumulative effect of the accounting change also includes the net unrealized gain on AFG’s small number of limited partnerships and similar investments carried at cost under the prior guidance that are carried at fair value through net earnings under the new guidance ( $4 million net of tax at the date of adoption). Holding gains and losses on equity securities carried at fair value under ASU 2016-01 are generally recorded in realized gains (losses) on securities. However, prior to the adoption of the new guidance, AFG classified a small portion of its equity securities as “trading” and reported those investments at fair value with holding gains and losses recognized in net investment income. These investments consisted primarily of equity securities held to offset the impact of changes in the stock market on employee benefit plans that are impacted by stock market performance and totaled $62 million at December 31, 2017. Following the adoption of the new guidance, AFG continues to record holding gains and losses on these securities, as well as its small portfolio of limited partnerships and similar investments carried at fair value under the new guidance and certain other securities classified at purchase as “fair value through net investment income” in net investment income. Under the new guidance, AFG recorded a net realized loss of $94 million on equity securities during the first three months of 2018 on securities that were still owned at March 31, 2018 . Under the prior guidance, this holding loss would have been recorded in AOCI (with the exception of any impairment charge that may have been recorded). Because almost all of the equity securities impacted by the new guidance were carried at fair value through AOCI under the prior guidance, the adoption of the new guidance did not have a material impact on AFG’s financial position. Fixed maturity 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 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. 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. Limited partnerships and similar investments are generally accounted for using the equity method of accounting. Under the equity method, AFG records its share of the earnings or losses of the investee based on when they are reported by the investee in its financial statements rather than in the period in which the investee declares a dividend. AFG’s share of the earnings or losses from equity method investments is generally recorded on a quarter lag due to the timing of the receipt of the investee’s financial statements. AFG’s equity in the earnings (losses) of limited partnerships and similar investments is included in net investment income. Gains or losses on fixed maturity 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 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 G — “ 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. 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.
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 annuity policy charges are recorded in 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 presented in its Balance Sheet as a direct reduction in the carrying value of long-term debt and are amortized over the life of the related debt using the effective interest method as a component of interest expense. Debt issuance costs related to AFG’s revolving credit facilities are included in other assets in AFG’s Balance Sheet.
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. 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. 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.
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. AFG records excess tax benefits or deficiencies for share-based payments through income tax expense in the statement of earnings. In addition, AFG accounts for forfeitures of awards when they occur.
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: first three months of 2018 and 2017 — 1.8 million and 2.1 million , respectively. There were no anti-dilutive potential common shares in the first three months of 2018 or 2017 .
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.
Revenue Recognition Guidance Effective in 2018	Revenue Recognition Guidance Effective in 2018 On January 1, 2018, AFG adopted ASU 2014-09, which provides guidance on recognizing revenue when (or as) performance obligations under the contract are satisfied. The new guidance also updates the accounting for certain costs associated with obtaining and fulfilling contracts with customers and requires certain new disclosures. Because revenue recognition for insurance contracts and financial instruments (AFG’s primary sources of revenue) were excluded from the scope of the new guidance, the adoption of ASU 2014-09 did not have a material impact on AFG’s results of operations or financial position.

Segments of Operations (Tables)

Segments of Operations (Tables)	3 Months Ended
	Mar. 31, 2018
Segment Reporting [Abstract]
Segment Reporting Information, by Segment	The following tables (in millions) show AFG’s revenues and earnings before income taxes by segment and sub-segment. Three months ended March 31, 2018 2017 Revenues Property and casualty insurance: Premiums earned: Specialty Property and transportation $ 350 $ 342 Specialty casualty 579 508 Specialty financial 149 147 Other specialty 29 25 Total premiums earned 1,107 1,022 Net investment income 100 86 Other income (a) 2 16 Total property and casualty insurance 1,209 1,124 Annuity: Net investment income 394 347 Other income 26 27 Total annuity 420 374 Other 83 75 Total revenues before realized gains (losses) 1,712 1,573 Realized gains (losses) on securities (93 ) 3 Total revenues $ 1,619 $ 1,576 Earnings Before Income Taxes Property and casualty insurance: Underwriting: Specialty Property and transportation $ 33 $ 43 Specialty casualty 41 15 Specialty financial 15 22 Other specialty 3 (1 ) Other lines (b) (1 ) (1 ) Total underwriting 91 78 Investment and other income, net (a) 93 93 Total property and casualty insurance 184 171 Annuity 125 96 Other (b) (42 ) (47 ) Total earnings before realized gains (losses) and income taxes 267 220 Realized gains (losses) on securities (93 ) 3 Total earnings before income taxes $ 174 $ 223 (a) Includes income of $13 million (before noncontrolling interest) from the sale of a hotel in the first quarter of 2017. (b) Includes holding company interest and expenses.

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	3 Months Ended
	Mar. 31, 2018
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 March 31, 2018 Assets: Available for sale (“AFS”) fixed maturities: U.S. Government and government agencies $ 147 $ 95 $ 8 $ 250 States, municipalities and political subdivisions — 6,941 62 7,003 Foreign government — 132 — 132 Residential MBS — 2,948 115 3,063 Commercial MBS — 893 47 940 Asset-backed securities — 7,751 912 8,663 Corporate and other 30 17,806 1,238 19,074 Total AFS fixed maturities 177 36,566 2,382 39,125 Trading fixed maturities 48 112 — 160 Equity securities 1,500 92 194 1,786 Equity index call options — 591 — 591 Assets of managed investment entities (“MIE”) 301 4,765 24 5,090 Variable annuity assets (separate accounts) (*) — 632 — 632 Total assets accounted for at fair value $ 2,026 $ 42,758 $ 2,600 $ 47,384 Liabilities: Liabilities of managed investment entities $ 287 $ 4,559 $ 23 $ 4,869 Derivatives in annuity benefits accumulated — — 2,549 2,549 Other liabilities — derivatives — 64 — 64 Total liabilities accounted for at fair value $ 287 $ 4,623 $ 2,572 $ 7,482 December 31, 2017 Assets: Available for sale 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 — 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 1,411 86 165 1,662 Equity index call options — 701 — 701 Assets of managed investment entities 307 4,572 23 4,902 Variable annuity assets (separate accounts) (*) — 644 — 644 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 (*) Variable annuity liabilities equal the fair value of variable annuity assets.
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 E — “ Derivatives .” Unobservable Input Range Adjustment for insurance subsidiary’s credit risk 0.1% – 1.7% 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% – 9% 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 balances of Level 3 financial assets	Changes in balances of Level 3 financial assets and liabilities carried at fair value during the first three months of 2018 and 2017 are presented below (in millions). The transfers into and out of Level 3 were due to changes in the availability of market observable inputs and $29 million of equity securities transferred into Level 3 in the first quarter of 2018 related to a small number of limited partnerships and similar investments carried at cost under the prior guidance that are carried at fair value through net earnings under new guidance adopted on January 1, 2018, as discussed in Note A — “ Accounting Policies — Investments .” 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, 2017 Net Other comprehensive income (loss) Purchases and issuances Sales and settlements Transfer into Level 3 Transfer out of Level 3 Balance at March 31, 2018 AFS fixed maturities: U.S. government agency $ 8 $ — $ — $ — $ — $ — $ — $ 8 State and municipal 148 — (1 ) — (1 ) — (84 ) 62 Residential MBS 122 (4 ) — — (6 ) 7 (4 ) 115 Commercial MBS 36 (1 ) — 12 — — — 47 Asset-backed securities 744 (2 ) 3 204 (37 ) — — 912 Corporate and other 1,044 1 (14 ) 238 (31 ) — — 1,238 Total AFS fixed maturities 2,102 (6 ) (12 ) 454 (75 ) 7 (88 ) 2,382 Equity securities 165 (5 ) — 9 (4 ) 29 — 194 Assets of MIE 23 (2 ) — 3 — — — 24 Total Level 3 assets $ 2,290 $ (13 ) $ (12 ) $ 466 $ (79 ) $ 36 $ (88 ) $ 2,600 Embedded derivatives $ (2,542 ) $ 63 $ — $ (103 ) $ 33 $ — $ — $ (2,549 ) Total Level 3 liabilities (*) $ (2,542 ) $ 63 $ — $ (103 ) $ 33 $ — $ — $ (2,549 ) Total realized/unrealized gains (losses) included in Balance at December 31, 2016 Net Other comprehensive income (loss) Purchases and issuances Sales and settlements Transfer into Level 3 Transfer out of Level 3 Balance at March 31, 2017 AFS fixed maturities: U.S. government agency $ 8 $ — $ — $ — $ — $ — $ — $ 8 State and municipal 140 — 3 — — — — 143 Residential MBS 190 1 — 1 (8 ) 7 (16 ) 175 Commercial MBS 25 — — — — 4 — 29 Asset-backed securities 484 — — 104 (11 ) 17 — 594 Corporate and other 712 1 4 120 (38 ) 29 — 828 Total AFS fixed maturities 1,559 2 7 225 (57 ) 57 (16 ) 1,777 Equity securities 174 (6 ) 7 12 — — (14 ) 173 Assets of MIE 29 (1 ) — 2 — — (4 ) 26 Total Level 3 assets $ 1,762 $ (5 ) $ 14 $ 239 $ (57 ) $ 57 $ (34 ) $ 1,976 Embedded derivatives $ (1,759 ) $ (147 ) $ — $ (79 ) $ 22 $ — $ — $ (1,963 ) Total Level 3 liabilities (*) $ (1,759 ) $ (147 ) $ — $ (79 ) $ 22 $ — $ — $ (1,963 ) (*) 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.
Changes in balances of Level 3 financial liabilities	Changes in balances of Level 3 financial assets and liabilities carried at fair value during the first three months of 2018 and 2017 are presented below (in millions). The transfers into and out of Level 3 were due to changes in the availability of market observable inputs and $29 million of equity securities transferred into Level 3 in the first quarter of 2018 related to a small number of limited partnerships and similar investments carried at cost under the prior guidance that are carried at fair value through net earnings under new guidance adopted on January 1, 2018, as discussed in Note A — “ Accounting Policies — Investments .” 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, 2017 Net Other comprehensive income (loss) Purchases and issuances Sales and settlements Transfer into Level 3 Transfer out of Level 3 Balance at March 31, 2018 AFS fixed maturities: U.S. government agency $ 8 $ — $ — $ — $ — $ — $ — $ 8 State and municipal 148 — (1 ) — (1 ) — (84 ) 62 Residential MBS 122 (4 ) — — (6 ) 7 (4 ) 115 Commercial MBS 36 (1 ) — 12 — — — 47 Asset-backed securities 744 (2 ) 3 204 (37 ) — — 912 Corporate and other 1,044 1 (14 ) 238 (31 ) — — 1,238 Total AFS fixed maturities 2,102 (6 ) (12 ) 454 (75 ) 7 (88 ) 2,382 Equity securities 165 (5 ) — 9 (4 ) 29 — 194 Assets of MIE 23 (2 ) — 3 — — — 24 Total Level 3 assets $ 2,290 $ (13 ) $ (12 ) $ 466 $ (79 ) $ 36 $ (88 ) $ 2,600 Embedded derivatives $ (2,542 ) $ 63 $ — $ (103 ) $ 33 $ — $ — $ (2,549 ) Total Level 3 liabilities (*) $ (2,542 ) $ 63 $ — $ (103 ) $ 33 $ — $ — $ (2,549 ) Total realized/unrealized gains (losses) included in Balance at December 31, 2016 Net Other comprehensive income (loss) Purchases and issuances Sales and settlements Transfer into Level 3 Transfer out of Level 3 Balance at March 31, 2017 AFS fixed maturities: U.S. government agency $ 8 $ — $ — $ — $ — $ — $ — $ 8 State and municipal 140 — 3 — — — — 143 Residential MBS 190 1 — 1 (8 ) 7 (16 ) 175 Commercial MBS 25 — — — — 4 — 29 Asset-backed securities 484 — — 104 (11 ) 17 — 594 Corporate and other 712 1 4 120 (38 ) 29 — 828 Total AFS fixed maturities 1,559 2 7 225 (57 ) 57 (16 ) 1,777 Equity securities 174 (6 ) 7 12 — — (14 ) 173 Assets of MIE 29 (1 ) — 2 — — (4 ) 26 Total Level 3 assets $ 1,762 $ (5 ) $ 14 $ 239 $ (57 ) $ 57 $ (34 ) $ 1,976 Embedded derivatives $ (1,759 ) $ (147 ) $ — $ (79 ) $ 22 $ — $ — $ (1,963 ) Total Level 3 liabilities (*) $ (1,759 ) $ (147 ) $ — $ (79 ) $ 22 $ — $ — $ (1,963 ) (*) 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.
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 are summarized below (in millions): Carrying Fair Value Value Total Level 1 Level 2 Level 3 March 31, 2018 Financial assets: Cash and cash equivalents $ 1,659 $ 1,659 $ 1,659 $ — $ — Mortgage loans 1,082 1,068 — — 1,068 Policy loans 181 181 — — 181 Total financial assets not accounted for at fair value $ 2,922 $ 2,908 $ 1,659 $ — $ 1,249 Financial liabilities: Annuity benefits accumulated (*) $ 33,692 $ 31,983 $ — $ — $ 31,983 Long-term debt 1,301 1,319 — 1,316 3 Total financial liabilities not accounted for at fair value $ 34,993 $ 33,302 $ — $ 1,316 $ 31,986 December 31, 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 (*) Excludes $209 million and $206 million of life contingent annuities in the payout phase at March 31, 2018 and December 31, 2017 , respectively.

Investments (Tables)

Investments (Tables)	3 Months Ended
	Mar. 31, 2018
Investments, Debt and Equity Securities [Abstract]
Available for sale fixed maturities	Available for sale fixed maturities at March 31, 2018 and December 31, 2017 , consisted of the following (in millions): March 31, 2018 December 31, 2017 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 $ 253 $ 1 $ (4 ) $ (3 ) $ 250 $ 244 $ 1 $ (3 ) $ (2 ) $ 242 States, municipalities and political subdivisions 6,855 187 (39 ) 148 7,003 6,887 254 (18 ) 236 7,123 Foreign government 130 2 — 2 132 124 3 — 3 127 Residential MBS 2,732 338 (7 ) 331 3,063 2,884 349 (6 ) 343 3,227 Commercial MBS 922 21 (3 ) 18 940 927 36 (1 ) 35 962 Asset-backed securities 8,546 148 (31 ) 117 8,663 7,836 142 (16 ) 126 7,962 Corporate and other 18,945 308 (179 ) 129 19,074 18,136 638 (38 ) 600 18,736 Total fixed maturities $ 38,383 $ 1,005 $ (263 ) $ 742 $ 39,125 $ 37,038 $ 1,423 $ (82 ) $ 1,341 $ 38,379
Equity securities reported at fair value	Equity securities reported at fair value consisted of the following at March 31, 2018 (in millions): Fair Value in Actual Cost Fair Value excess of Cost Common stocks $ 1,099 $ 1,154 $ 55 Perpetual preferred stocks 632 632 — Total equity securities carried at fair value $ 1,731 $ 1,786 $ 55
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 the following balance sheet dates. 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 March 31, 2018 Fixed maturities: U.S. Government and government agencies $ (1 ) $ 57 98 % $ (3 ) $ 119 98 % States, municipalities and political subdivisions (26 ) 1,745 99 % (13 ) 411 97 % Foreign government — 22 100 % — — — % Residential MBS (3 ) 155 98 % (4 ) 114 97 % Commercial MBS (3 ) 148 98 % — — — % Asset-backed securities (21 ) 2,586 99 % (10 ) 306 97 % Corporate and other (149 ) 7,352 98 % (30 ) 601 95 % Total fixed maturities $ (203 ) $ 12,065 98 % $ (60 ) $ 1,551 96 % December 31, 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 %
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): 2018 2017 Balance at January 1 $ 145 $ 153 Additional credit impairments on: Previously impaired securities — — Securities without prior impairments — — Reductions due to sales or redemptions (1 ) (7 ) Balance at March 31 $ 144 $ 146
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 March 31, 2018 (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 $ 793 $ 804 2 % After one year through five years 7,314 7,431 19 % After five years through ten years 13,345 13,425 35 % After ten years 4,731 4,799 12 % 26,183 26,459 68 % ABS (average life of approximately 4-1/2 years) 8,546 8,663 22 % MBS (average life of approximately 4-1/2 years) 3,654 4,003 10 % Total $ 38,383 $ 39,125 100 %
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 March 31, 2018 Net unrealized gain on: Fixed maturities — annuity segment (a) $ 594 $ (125 ) $ 469 Fixed maturities — all other 148 (31 ) 117 Total fixed maturities 742 (156 ) 586 Deferred policy acquisition costs — annuity segment (236 ) 49 (187 ) Annuity benefits accumulated (79 ) 17 (62 ) Unearned revenue 6 (1 ) 5 Total net unrealized gain on marketable securities $ 433 $ (91 ) $ 342 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 (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 other than those accounted for under the equity method are carried at fair value through net earnings.
Net investment income earned and investment expenses incurred	The following table shows (in millions) investment income earned and investment expenses incurred. Three months ended March 31, 2018 2017 Investment income: Fixed maturities $ 412 $ 389 Equity securities 19 21 Equity in earnings of partnerships and similar investments 46 10 Other 23 20 Gross investment income 500 440 Investment expenses (5 ) (5 ) Net investment income $ 495 $ 435
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): Three months ended March 31, 2018 Three months ended March 31, 2017 Realized gains (losses) Realized gains (losses) Before Impairments Impairments Total Change in Unrealized Before Impairments Impairments Total Change in Unrealized Fixed maturities $ (1 ) $ (1 ) $ (2 ) $ (599 ) $ 5 $ — $ 5 $ 202 Equity securities (a) (95 ) — (95 ) — 2 (9 ) (7 ) 72 Mortgage loans and other investments — — — — 3 — 3 — Other (b) 4 — 4 248 (1 ) 3 2 (83 ) Total pretax (92 ) (1 ) (93 ) (351 ) 9 (6 ) 3 191 Tax effects 20 — 20 74 (3 ) 2 (1 ) (66 ) Net of tax $ (72 ) $ (1 ) $ (73 ) $ (277 ) $ 6 $ (4 ) $ 2 $ 125 (a) As discussed in Note A — “ Accounting Policies — Investments ,” effective January 1, 2018, all equity securities other than those accounted for under the equity method are carried at fair value through net earnings. AFG recorded a net realized loss of $94 million on equity securities during the first three months of 2018 on securities that were still owned at March 31, 2018 . (b) 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 investment transactions consisted of the following (in millions): Three months ended March 31, 2018 2017 Fixed maturities: Gross gains $ 6 $ 5 Gross losses (3 ) —

Derivatives (Tables)

Derivatives (Tables)	3 Months Ended
	Mar. 31, 2018
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): March 31, 2018 December 31, 2017 Derivative Balance Sheet Line Asset Liability Asset Liability MBS with embedded derivatives Fixed maturities $ 111 $ — $ 105 $ — Public company warrants Equity securities 3 — 4 — Fixed-indexed annuities (embedded derivative) Annuity benefits accumulated — 2,549 — 2,542 Equity index call options Equity index call options 591 — 701 — Reinsurance contracts (embedded derivative) Other liabilities — 3 — 4 $ 705 $ 2,552 $ 810 $ 2,546
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 the first three months of 2018 and 2017 (in millions): Three months ended March 31, Derivative Statement of Earnings Line 2018 2017 MBS with embedded derivatives Realized gains on securities $ (4 ) $ — Public company warrants Realized gains on securities (1 ) — Fixed-indexed annuities (embedded derivative) Annuity benefits 63 (147 ) Equity index call options Annuity benefits (38 ) 141 Reinsurance contract (embedded derivative) Net investment income 1 (1 ) $ 21 $ (7 )

Deferred Policy Acquisition C27

Deferred Policy Acquisition Costs (Tables)	3 Months Ended
	Mar. 31, 2018
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 Other Deferred Deferred Sales Consolidated Costs Costs Inducements PVFP Subtotal Unrealized (*) Total Total Balance at December 31, 2017 $ 270 $ 1,217 $ 102 $ 49 $ 1,368 $ (422 ) $ 946 $ 1,216 Additions 162 57 — — 57 — 57 219 Amortization: Periodic amortization (154 ) (69 ) (5 ) (2 ) (76 ) — (76 ) (230 ) Included in realized gains — 3 — — 3 — 3 3 Foreign currency translation 1 — — — — — — 1 Change in unrealized — — — — — 208 208 208 Balance at March 31, 2018 $ 279 $ 1,208 $ 97 $ 47 $ 1,352 $ (214 ) $ 1,138 $ 1,417 Balance at December 31, 2016 $ 238 $ 1,110 $ 110 $ 46 $ 1,266 $ (265 ) $ 1,001 $ 1,239 Additions 139 67 1 — 68 — 68 207 Amortization: Periodic amortization (135 ) (42 ) (6 ) (2 ) (50 ) — (50 ) (185 ) Included in realized gains — 2 — — 2 — 2 2 Foreign currency translation 1 — — — — — — 1 Change in unrealized — — — — — (59 ) (59 ) (59 ) Balance at March 31, 2017 $ 243 $ 1,137 $ 105 $ 44 $ 1,286 $ (324 ) $ 962 $ 1,205 (*) 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)	3 Months Ended
	Mar. 31, 2018
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): Three months ended March 31, 2018 2017 Investment in CLO tranches at end of period $ 221 $ 230 Gains (losses) on change in fair value of assets/liabilities (a): Assets 14 5 Liabilities (17 ) (5 ) Management fees paid to AFG 4 4 CLO earnings (losses) attributable to AFG shareholders (b) 3 6 (a) Included in revenues in AFG’s Statement of Earnings. (b) Included in earnings before income taxes in AFG’s Statement of Earnings.

Long-Term Debt (Tables)

Long-Term Debt (Tables)	3 Months Ended
	Mar. 31, 2018
Debt Disclosure [Abstract]
Schedule of long-term debt instruments	Long-term debt consisted of the following (in millions): March 31, 2018 December 31, 2017 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 $ 590 $ (2 ) $ 588 3.50% Senior Notes due August 2026 425 (5 ) 420 425 (5 ) 420 Other 3 — 3 3 — 3 1,018 (7 ) 1,011 1,018 (7 ) 1,011 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 $ 1,318 $ (17 ) $ 1,301

Shareholders' Equity (Tables)

Shareholders' Equity (Tables)	3 Months Ended
	Mar. 31, 2018
Stockholders' Equity Note [Abstract]
Components of accumulated other comprehensive income (loss)	The progression of the components of accumulated other comprehensive income follows (in millions): Other Comprehensive Income (Loss) AOCI Beginning Balance Pretax Tax Net of tax Attributable to noncontrolling interests Attributable to shareholders Other (c) AOCI Ending Balance Three months ended March 31, 2018 Net unrealized gains (losses) on securities: Unrealized holding losses on securities arising during the period $ (353 ) $ 74 $ (279 ) $ — $ (279 ) Reclassification adjustment for realized (gains) losses included in net earnings (a) 2 — 2 — 2 Total net unrealized gains (losses) on securities (b) $ 840 (351 ) 74 (277 ) — (277 ) $ (221 ) $ 342 Net unrealized losses on cash flow hedges (13 ) (14 ) 3 (11 ) — (11 ) — (24 ) Foreign currency translation adjustments (6 ) 2 (1 ) 1 — 1 — (5 ) Pension and other postretirement plans adjustments (8 ) — — — — — — (8 ) Total $ 813 $ (363 ) $ 76 $ (287 ) $ — $ (287 ) $ (221 ) $ 305 Three months ended March 31, 2017 Net unrealized gains on securities: Unrealized holding gains on securities arising during the period $ 191 $ (66 ) $ 125 $ — $ 125 Reclassification adjustment for realized (gains) losses included in net earnings (a) — — — — — Total net unrealized gains on securities $ 404 191 (66 ) 125 — 125 $ — $ 529 Net unrealized losses on cash flow hedges (7 ) (2 ) 1 (1 ) — (1 ) — (8 ) Foreign currency translation adjustments (15 ) — — — — — — (15 ) Pension and other postretirement plans adjustments (7 ) — — — — — — (7 ) Total $ 375 $ 189 $ (65 ) $ 124 $ — $ 124 $ — $ 499 (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 (b) Includes net unrealized gains of $68 million at both March 31, 2018 and December 31, 2017 related to securities for which only the credit portion of an other-than-temporary impairment has been recorded in earnings. (c) On January 1, 2018, AFG adopted new guidance that requires all equity securities other than those accounted for under the equity method to be reported at fair value with holding gains and losses recognized in net earnings. At the date of adoption, the $221 million net unrealized gain on equity securities classified as available for sale (with unrealized holding gains and losses reported in AOCI) under the prior guidance was reclassified from AOCI to retained earnings as the cumulative effect of an accounting change.

Income Taxes (Tables)

Income Taxes (Tables)	3 Months Ended
	Mar. 31, 2018
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 ( 21% in 2018 and 35% in 2017 ) to the provision for income taxes as shown in AFG’s Statement of Earnings (dollars in millions): Three months ended March 31, 2018 2017 Amount % of EBT Amount % of EBT Earnings before income taxes (“EBT”) $ 174 $ 223 Income taxes at statutory rate $ 37 21 % $ 78 35 % Effect of: Stock-based compensation (5 ) (3 %) (6 ) (3 %) Tax exempt interest (3 ) (2 %) (6 ) (3 %) Dividends received deduction (1 ) — % (2 ) (1 %) Foreign operations 3 2 % 6 3 % Nondeductible expenses 2 1 % 2 1 % Change in valuation allowance — — % (2 ) (1 %) Other — — % (2 ) (1 %) Provision for income taxes as shown in the statement of earnings $ 33 19 % $ 68 30 %

Insurance (Tables)

Insurance (Tables)	3 Months Ended
	Mar. 31, 2018
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 during the first three months of 2018 and 2017 (in millions): Three months ended March 31, 2018 2017 Balance at beginning of year $ 9,678 $ 8,563 Less reinsurance recoverables, net of allowance 2,957 2,302 Net liability at beginning of year 6,721 6,261 Provision for losses and LAE occurring in the current period 697 637 Net decrease in the provision for claims of prior years (56 ) (28 ) Total losses and LAE incurred 641 609 Payments for losses and LAE of: Current year (86 ) (84 ) Prior years (554 ) (470 ) Total payments (640 ) (554 ) Reserves of business disposed (*) (319 ) — Foreign currency translation and other 2 8 Net liability at end of period 6,405 6,324 Add back reinsurance recoverables, net of allowance 2,788 2,297 Gross unpaid losses and LAE included in the balance sheet at end of period $ 9,193 $ 8,621

Accounting Policies - Narrative

Accounting Policies - Narrative (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2018	Mar. 31, 2017	Jan. 01, 2018	Dec. 31, 2017
Significant Accounting Policies [Line Items]
Net unrealized gain on equity securities included in AOCI		$ 342			$ 840
Cumulative effect of accounting change					4
Realized gains (losses) on securities		$ (93)	$ 3
Weighted average common shares adjustment related to stock-based compensation (shares)		1,800,000	2,100,000
Anti-dilutive potential common shares related to stock-based compensation plans (shares)		0	0
Maturities of short term investments		3 months
Equity securities
Significant Accounting Policies [Line Items]
Available-for-sale securities, Equity securities					1,600
Net unrealized gain on equity securities included in AOCI	[1]				221
Equity securities, trading at fair value					62
Realized gains (losses) on securities	[2]	$ (95)	$ (7)
Equity securities | Accounting Standards Update 2016-01
Significant Accounting Policies [Line Items]
Net unrealized gain on equity securities included in AOCI					$ 221
Cumulative effect of accounting change				$ (221)
Realized gains (losses) on securities		$ (94)
Limited partnerships and similar investments | Accounting Standards Update 2016-01
Significant Accounting Policies [Line Items]
Cumulative effect of accounting change				$ (4)
[1]	As discussed in Note A — “Accounting Policies — Investments,” effective January 1, 2018, all equity securities other than those accounted for under the equity method are carried at fair value through net earnings.
[2]	As discussed in Note A — “Accounting Policies — Investments,” effective January 1, 2018, all equity securities other than those accounted for under the equity method are carried at fair value through net earnings. AFG recorded a net realized loss of $94 million on equity securities during the first three months of 2018 on securities that were still owned at March 31, 2018.

Segments of Operations - Narrat

Segments of Operations - Narrative (Details) $ in Millions	3 Months Ended
	Mar. 31, 2018segment	Mar. 31, 2017USD ($)
Segment Reporting Information [Line Items]
Number of segments | segment	3
Property and Casualty Insurance | Real Estate Investment
Segment Reporting Information [Line Items]
Pretax income from the sale of real estate properties | $		$ 13

Segments of Operations - Revenu

Segments of Operations - Revenues by segment and sub-segment (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2018	Mar. 31, 2017
Segment Reporting Information [Line Items]
Total premiums earned		$ 1,107	$ 1,022
Net investment income		495	435
Other income		49	59
Revenues before realized gains (losses)		1,712	1,573
Realized gains (losses) on securities		(93)	3
Total revenues		1,619	1,576
Property and Casualty Insurance
Segment Reporting Information [Line Items]
Total premiums earned		1,107	1,022
Net investment income		100	86
Other income	[1]	2	16
Revenues before realized gains (losses)		1,209	1,124
Annuity
Segment Reporting Information [Line Items]
Net investment income		394	347
Other income		26	27
Revenues before realized gains (losses)		420	374
Other
Segment Reporting Information [Line Items]
Revenues before realized gains (losses)		83	75
Specialty Property and transportation | Property and Casualty Insurance
Segment Reporting Information [Line Items]
Total premiums earned		350	342
Specialty casualty | Property and Casualty Insurance
Segment Reporting Information [Line Items]
Total premiums earned		579	508
Specialty financial | Property and Casualty Insurance
Segment Reporting Information [Line Items]
Total premiums earned		149	147
Other specialty | Property and Casualty Insurance
Segment Reporting Information [Line Items]
Total premiums earned		$ 29	$ 25
[1]	Includes income of $13 million (before noncontrolling interest) from the sale of a hotel in the first quarter of 2017.

Segments of Operations - Earnin

Segments of Operations - Earnings before income taxes by segment and sub-segment (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2018	Mar. 31, 2017
Segment Reporting Information [Line Items]
Earnings before realized gains (losses) and income taxes		$ 267	$ 220
Realized gains (losses) on securities		(93)	3
Earnings before income taxes		174	223
Property and Casualty Insurance
Segment Reporting Information [Line Items]
Property and casualty insurance underwriting		91	78
Investment and other income, net	[1]	93	93
Earnings before realized gains (losses) and income taxes		184	171
Annuity
Segment Reporting Information [Line Items]
Earnings before realized gains (losses) and income taxes		125	96
Other
Segment Reporting Information [Line Items]
Earnings before realized gains (losses) and income taxes		(42)	(47)
Specialty Property and transportation | Property and Casualty Insurance
Segment Reporting Information [Line Items]
Property and casualty insurance underwriting		33	43
Specialty casualty | Property and Casualty Insurance
Segment Reporting Information [Line Items]
Property and casualty insurance underwriting		41	15
Specialty financial | Property and Casualty Insurance
Segment Reporting Information [Line Items]
Property and casualty insurance underwriting		15	22
Other specialty | Property and Casualty Insurance
Segment Reporting Information [Line Items]
Property and casualty insurance underwriting		3	(1)
Other lines | Property and Casualty Insurance
Segment Reporting Information [Line Items]
Property and casualty insurance underwriting	[2]	$ (1)	$ (1)
[1]	Includes income of $13 million (before noncontrolling interest) from the sale of a hotel in the first quarter of 2017.
[2]	Includes holding company interest and expenses.

Fair Value Measurements - Narra

Fair Value Measurements - Narrative (Details) $ in Millions	3 Months Ended
	Mar. 31, 2018USD ($)professional	Mar. 31, 2017USD ($)	Dec. 31, 2017USD ($)
Fair Value Measurements (Textual) [Abstract]
AFG's internal investment professionals | professional	25
Fair Value of assets transferred from Level 1 to Level 2, during the first three months	$ 0
Fair Value of assets transferred from Level 2 to Level 1, during the first three months	$ 0
Level 3 assets as a percentage of total assets measured at fair value	6.00%
Percentage of level 3 assets that were priced using non-binding broker quotes	78.00%
Level 3 assets that were priced using non-binding broker quotes	$ 2,030
Fair value of equity securities transferred into Level 3	36	$ 57
Life contingent annuities	$ 209		$ 206
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 annuties (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 annuties (embedded derivative), majority of future years | Maximum
Fair Value Measurements (Textual) [Abstract]
Unobservable input surrenders used in Level 3 fair value determination	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	$ 2,550
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%
Equity securities
Fair Value Measurements (Textual) [Abstract]
Fair value of equity securities transferred into Level 3	$ 29	$ 0

Fair Value Measurements - Asset

Fair Value Measurements - Assets and liabilities measured and carried at fair value in the financial statements (Details) - USD ($) $ in Millions		Mar. 31, 2018	Dec. 31, 2017
Assets:
Available for sale (AFS) fixed maturities		$ 39,125	$ 38,379
Trading fixed maturities		160	348
Equity index call options		591	701
Assets of managed investment entities (“MIE”)		5,090	4,902
Variable annuity assets (separate accounts)	[1]	632	644
Total assets accounted for at fair value		47,384	46,636
Liabilities:
Liabilities of managed investment entities		4,869	4,687
Total liabilities accounted for at fair value		7,482	7,264
Annuity benefits accumulated
Liabilities:
Derivatives included in annuity benefits accumulated, long-term debt, and other liabilities		2,549	2,542
Other liabilities — derivatives
Liabilities:
Derivatives included in annuity benefits accumulated, long-term debt, and other liabilities		64	35
Fixed maturities
Assets:
Available for sale (AFS) fixed maturities		39,125	38,379
Trading fixed maturities		160	348
U.S. Government and government agencies
Assets:
Available for sale (AFS) fixed maturities		250	242
States, municipalities and political subdivisions
Assets:
Available for sale (AFS) fixed maturities		7,003	7,123
Foreign government
Assets:
Available for sale (AFS) fixed maturities		132	127
Residential MBS
Assets:
Available for sale (AFS) fixed maturities		3,063	3,227
Commercial MBS
Assets:
Available for sale (AFS) fixed maturities		940	962
Asset-backed securities
Assets:
Available for sale (AFS) fixed maturities		8,663	7,962
Corporate and other
Assets:
Available for sale (AFS) fixed maturities		19,074	18,736
Equity securities
Assets:
Equity securities		1,786	1,662
Level 1
Assets:
Assets of managed investment entities (“MIE”)		301	307
Variable annuity assets (separate accounts)	[1]	0	0
Total assets accounted for at fair value		2,026	1,914
Liabilities:
Liabilities of managed investment entities		287	293
Total liabilities accounted for at fair value		287	293
Level 1 | Annuity benefits accumulated
Liabilities:
Derivatives included in annuity benefits accumulated, long-term debt, and other liabilities		0	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		177	152
Trading fixed maturities		48	44
Level 1 | U.S. Government and government agencies
Assets:
Available for sale (AFS) fixed maturities		147	122
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
Assets:
Available for sale (AFS) fixed maturities		0	0
Level 1 | Corporate and other
Assets:
Available for sale (AFS) fixed maturities		30	30
Level 1 | Equity securities
Assets:
Equity securities		1,500	1,411
Level 2
Assets:
Assets of managed investment entities (“MIE”)		4,765	4,572
Variable annuity assets (separate accounts)	[1]	632	644
Total assets accounted for at fair value		42,758	42,432
Liabilities:
Liabilities of managed investment entities		4,559	4,372
Total liabilities accounted for at fair value		4,623	4,407
Level 2 | Annuity benefits accumulated
Liabilities:
Derivatives included in annuity benefits accumulated, long-term debt, and other liabilities		0	0
Level 2 | Other liabilities — derivatives
Liabilities:
Derivatives included in annuity benefits accumulated, long-term debt, and other liabilities		64	35
Level 2 | Fixed maturities
Assets:
Available for sale (AFS) fixed maturities		36,566	36,125
Trading fixed maturities		112	304
Level 2 | U.S. Government and government agencies
Assets:
Available for sale (AFS) fixed maturities		95	112
Level 2 | States, municipalities and political subdivisions
Assets:
Available for sale (AFS) fixed maturities		6,941	6,975
Level 2 | Foreign government
Assets:
Available for sale (AFS) fixed maturities		132	127
Level 2 | Residential MBS
Assets:
Available for sale (AFS) fixed maturities		2,948	3,105
Level 2 | Commercial MBS
Assets:
Available for sale (AFS) fixed maturities		893	926
Level 2 | Asset-backed securities
Assets:
Available for sale (AFS) fixed maturities		7,751	7,218
Level 2 | Corporate and other
Assets:
Available for sale (AFS) fixed maturities		17,806	17,662
Level 2 | Equity securities
Assets:
Equity securities		92	86
Level 3
Assets:
Assets of managed investment entities (“MIE”)		24	23
Variable annuity assets (separate accounts)	[1]	0	0
Total assets accounted for at fair value		2,600	2,290
Liabilities:
Liabilities of managed investment entities		23	22
Total liabilities accounted for at fair value		2,572	2,564
Level 3 | Annuity benefits accumulated
Liabilities:
Derivatives included in annuity benefits accumulated, long-term debt, and other liabilities		2,549	2,542
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		2,382	2,102
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		62	148
Level 3 | Foreign government
Assets:
Available for sale (AFS) fixed maturities		0	0
Level 3 | Residential MBS
Assets:
Available for sale (AFS) fixed maturities		115	122
Level 3 | Commercial MBS
Assets:
Available for sale (AFS) fixed maturities		47	36
Level 3 | Asset-backed securities
Assets:
Available for sale (AFS) fixed maturities		912	744
Level 3 | Corporate and other
Assets:
Available for sale (AFS) fixed maturities		1,238	1,044
Level 3 | Equity securities
Assets:
Equity securities		194	165
Equity index call options | Equity index call options
Assets:
Equity index call options		591	701
Equity index call options | Level 1 | Equity index call options
Assets:
Equity index call options		0	0
Equity index call options | Level 2 | Equity index call options
Assets:
Equity index call options		591	701
Equity index call options | Level 3 | Equity index call options
Assets:
Equity index call options		$ 0	$ 0
[1]	Variable annuity liabilities equal the fair value of variable annuity assets.

Fair Value Measurements - Unobs

Fair Value Measurements - Unobservable inputs used in determining fair value of embedded derivatives (Details) - Embedded derivatives	3 Months Ended
	Mar. 31, 2018
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	0.10%
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	1.70%
Surrenders	23.00%
Partial surrenders	9.00%
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	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Financial assets, Beginning Balance	$ 2,290	$ 1,762
Total realized/unrealized gains (losses) included in Net income	(13)	(5)
Total realized/unrealized gains (losses) included in other comprehensive income (loss)	(12)	14
Purchases and issuances	466	239
Sales and settlements	(79)	(57)
Transfer into Level 3	36	57
Transfer out of Level 3	(88)	(34)
Financial assets, Ending Balance	2,600	1,976
Fixed maturities
Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Financial assets, Beginning Balance	2,102	1,559
Total realized/unrealized gains (losses) included in Net income	(6)	2
Total realized/unrealized gains (losses) included in other comprehensive income (loss)	(12)	7
Purchases and issuances	454	225
Sales and settlements	(75)	(57)
Transfer into Level 3	7	57
Transfer out of Level 3	(88)	(16)
Financial assets, Ending Balance	2,382	1,777
U.S. government agency
Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Financial assets, Beginning Balance	8	8
Total realized/unrealized gains (losses) included in Net income	0	0
Total realized/unrealized gains (losses) included in other comprehensive income (loss)	0	0
Purchases and issuances	0	0
Sales and settlements	0	0
Transfer into Level 3	0	0
Transfer out of Level 3	0	0
Financial assets, Ending Balance	8	8
State and municipal
Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Financial assets, Beginning Balance	148	140
Total realized/unrealized gains (losses) included in Net income	0	0
Total realized/unrealized gains (losses) included in other comprehensive income (loss)	(1)	3
Purchases and issuances	0	0
Sales and settlements	(1)	0
Transfer into Level 3	0	0
Transfer out of Level 3	(84)	0
Financial assets, Ending Balance	62	143
Residential MBS
Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Financial assets, Beginning Balance	122	190
Total realized/unrealized gains (losses) included in Net income	(4)	1
Total realized/unrealized gains (losses) included in other comprehensive income (loss)	0	0
Purchases and issuances	0	1
Sales and settlements	(6)	(8)
Transfer into Level 3	7	7
Transfer out of Level 3	(4)	(16)
Financial assets, Ending Balance	115	175
Commercial MBS
Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Financial assets, Beginning Balance	36	25
Total realized/unrealized gains (losses) included in Net income	(1)	0
Total realized/unrealized gains (losses) included in other comprehensive income (loss)	0	0
Purchases and issuances	12	0
Sales and settlements	0	0
Transfer into Level 3	0	4
Transfer out of Level 3	0	0
Financial assets, Ending Balance	47	29
Asset-backed securities
Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Financial assets, Beginning Balance	744	484
Total realized/unrealized gains (losses) included in Net income	(2)	0
Total realized/unrealized gains (losses) included in other comprehensive income (loss)	3	0
Purchases and issuances	204	104
Sales and settlements	(37)	(11)
Transfer into Level 3	0	17
Transfer out of Level 3	0	0
Financial assets, Ending Balance	912	594
Corporate and other
Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Financial assets, Beginning Balance	1,044	712
Total realized/unrealized gains (losses) included in Net income	1	1
Total realized/unrealized gains (losses) included in other comprehensive income (loss)	(14)	4
Purchases and issuances	238	120
Sales and settlements	(31)	(38)
Transfer into Level 3	0	29
Transfer out of Level 3	0	0
Financial assets, Ending Balance	1,238	828
Equity securities
Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Financial assets, Beginning Balance	165	174
Total realized/unrealized gains (losses) included in Net income	(5)	(6)
Total realized/unrealized gains (losses) included in other comprehensive income (loss)	0	7
Purchases and issuances	9	12
Sales and settlements	(4)	0
Transfer into Level 3	29	0
Transfer out of Level 3	0	(14)
Financial assets, Ending Balance	194	173
Assets of MIE
Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Financial assets, Beginning Balance	23	29
Total realized/unrealized gains (losses) included in Net income	(2)	(1)
Total realized/unrealized gains (losses) included in other comprehensive income (loss)	0	0
Purchases and issuances	3	2
Sales and settlements	0	0
Transfer into Level 3	0	0
Transfer out of Level 3	0	(4)
Financial assets, Ending Balance	$ 24	$ 26

Fair Value Measurements - Cha41

Fair Value Measurements - Changes in balances of Level 3 financial liabilities carried at fair value (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2018	Mar. 31, 2017
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Financial liabilities, Beginning Balance		$ (2,542)	$ (1,759)
Total realized/unrealized gains (losses) included in Net income		63	(147)
Total realized/unrealized gains (losses) included in other comprehensive income (loss)		0	0
Purchases and issuances		(103)	(79)
Sales and settlements		33	22
Transfer into Level 3		0	0
Transfer out of Level 3		0	0
Financial liabilities, Ending Balance	[1]	(2,549)	(1,963)
Embedded derivatives
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Financial liabilities, Beginning Balance		(2,542)	(1,759)
Total realized/unrealized gains (losses) included in Net income		63	(147)
Total realized/unrealized gains (losses) included in other comprehensive income (loss)		0	0
Purchases and issuances		(103)	(79)
Sales and settlements		33	22
Transfer into Level 3		0	0
Transfer out of Level 3		0	0
Financial liabilities, Ending Balance		$ (2,549)	$ (1,963)
[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.

Fair Value Measurements - The c

Fair Value Measurements - The carrying value and fair value of financial instruments (Details) - USD ($) $ in Millions		Mar. 31, 2018	Dec. 31, 2017
Financial assets:
Mortgage loans		$ 1,082	$ 1,125
Policy loans		181	184
Financial liabilities:
Long-term debt		1,301	1,301
Level 1
Financial assets:
Cash and cash equivalents		1,659	2,338
Mortgage loans		0	0
Policy loans		0	0
Total financial assets not accounted for at fair value		1,659	2,338
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		1,316	1,351
Total financial liabilities not accounted for at fair value		1,316	1,351
Level 3
Financial assets:
Cash and cash equivalents		0	0
Mortgage loans		1,068	1,119
Policy loans		181	184
Total financial assets not accounted for at fair value		1,249	1,303
Financial liabilities:
Annuity benefits accumulated	[1]	31,983	32,461
Long-term debt		3	3
Total financial liabilities not accounted for at fair value		31,986	32,464
Carrying Value
Financial assets:
Cash and cash equivalents		1,659	2,338
Mortgage loans		1,082	1,125
Policy loans		181	184
Total financial assets not accounted for at fair value		2,922	3,647
Financial liabilities:
Annuity benefits accumulated	[1]	33,692	33,110
Long-term debt		1,301	1,301
Total financial liabilities not accounted for at fair value		34,993	34,411
Fair Value
Financial assets:
Cash and cash equivalents		1,659	2,338
Mortgage loans		1,068	1,119
Policy loans		181	184
Total financial assets not accounted for at fair value		2,908	3,641
Financial liabilities:
Annuity benefits accumulated	[1]	31,983	32,461
Long-term debt		1,319	1,354
Total financial liabilities not accounted for at fair value		$ 33,302	$ 33,815
[1]	Excludes $209 million and $206 million of life contingent annuities in the payout phase at March 31, 2018 and December 31, 2017, respectively.

Investments - Narrative (Detail

Investments - Narrative (Details) $ in Millions		3 Months Ended
		Mar. 31, 2018USD ($)security	Mar. 31, 2017USD ($)	Dec. 31, 2017USD ($)
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		90.00%
Percentage (based on fair value) of available for sale fixed maturities that are in an unrealized loss position and rated investment grade		94.00%
Other than temporary impairment charges		$ 1	$ 6
Residential MBS
Investment [Line Items]
Non-credit related portion of other-than-temporary impairment charges taken for securities still owned		155		$ 158
Gross unrealized losses on fixed maturities		(7)		(6)
Other than temporary impairment charges		1
Securities with non-credit other-than-temporary impairment charges
Investment [Line Items]
Gross unrealized gains		136		137
Gross unrealized losses		(4)		(4)
Fixed maturities
Investment [Line Items]
Gross unrealized losses on fixed maturities		$ (263)		$ (82)
Number of available for sale securities in an unrealized loss position | security		1,621
Other than temporary impairment charges		$ 1	0
Gross gains		6	5
Gross losses		(3)	0
Corporate bonds
Investment [Line Items]
Other than temporary impairment charges		1
Equity securities
Investment [Line Items]
Other than temporary impairment charges	[1]	$ 0	9
Gross gains			4
Gross losses			$ (2)
[1]	As discussed in Note A — “Accounting Policies — Investments,” effective January 1, 2018, all equity securities other than those accounted for under the equity method are carried at fair value through net earnings. AFG recorded a net realized loss of $94 million on equity securities during the first three months of 2018 on securities that were still owned at March 31, 2018.

Investments - Available for sal

Investments - Available for sale fixed maturities (Details) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Schedule of Available-for-sale Securities [Line Items]
Fixed maturities, Available for sale, Amortized Cost	$ 38,383	$ 37,038
Available for sale (AFS) fixed maturities	39,125	38,379
Total fixed maturities
Schedule of Available-for-sale Securities [Line Items]
Fixed maturities, Available for sale, Amortized Cost	38,383	37,038
Fixed maturities, Available for sale, Gross Unrealized, Gains	1,005	1,423
Fixed maturities, Available for sale, Gross Unrealized, Losses	(263)	(82)
Fixed maturities, Available for sale, Net Unrealized, Gains (Losses)	742	1,341
Available for sale (AFS) fixed maturities	39,125	38,379
U.S. Government and government agencies
Schedule of Available-for-sale Securities [Line Items]
Fixed maturities, Available for sale, Amortized Cost	253	244
Fixed maturities, Available for sale, Gross Unrealized, Gains	1	1
Fixed maturities, Available for sale, Gross Unrealized, Losses	(4)	(3)
Fixed maturities, Available for sale, Net Unrealized, Gains (Losses)	(3)	(2)
Available for sale (AFS) fixed maturities	250	242
States, municipalities and political subdivisions
Schedule of Available-for-sale Securities [Line Items]
Fixed maturities, Available for sale, Amortized Cost	6,855	6,887
Fixed maturities, Available for sale, Gross Unrealized, Gains	187	254
Fixed maturities, Available for sale, Gross Unrealized, Losses	(39)	(18)
Fixed maturities, Available for sale, Net Unrealized, Gains (Losses)	148	236
Available for sale (AFS) fixed maturities	7,003	7,123
Foreign government
Schedule of Available-for-sale Securities [Line Items]
Fixed maturities, Available for sale, Amortized Cost	130	124
Fixed maturities, Available for sale, Gross Unrealized, Gains	2	3
Fixed maturities, Available for sale, Gross Unrealized, Losses	0	0
Fixed maturities, Available for sale, Net Unrealized, Gains (Losses)	2	3
Available for sale (AFS) fixed maturities	132	127
Residential MBS
Schedule of Available-for-sale Securities [Line Items]
Fixed maturities, Available for sale, Amortized Cost	2,732	2,884
Fixed maturities, Available for sale, Gross Unrealized, Gains	338	349
Fixed maturities, Available for sale, Gross Unrealized, Losses	(7)	(6)
Fixed maturities, Available for sale, Net Unrealized, Gains (Losses)	331	343
Available for sale (AFS) fixed maturities	3,063	3,227
Commercial MBS
Schedule of Available-for-sale Securities [Line Items]
Fixed maturities, Available for sale, Amortized Cost	922	927
Fixed maturities, Available for sale, Gross Unrealized, Gains	21	36
Fixed maturities, Available for sale, Gross Unrealized, Losses	(3)	(1)
Fixed maturities, Available for sale, Net Unrealized, Gains (Losses)	18	35
Available for sale (AFS) fixed maturities	940	962
Asset-backed securities
Schedule of Available-for-sale Securities [Line Items]
Fixed maturities, Available for sale, Amortized Cost	8,546	7,836
Fixed maturities, Available for sale, Gross Unrealized, Gains	148	142
Fixed maturities, Available for sale, Gross Unrealized, Losses	(31)	(16)
Fixed maturities, Available for sale, Net Unrealized, Gains (Losses)	117	126
Available for sale (AFS) fixed maturities	8,663	7,962
Corporate and other
Schedule of Available-for-sale Securities [Line Items]
Fixed maturities, Available for sale, Amortized Cost	18,945	18,136
Fixed maturities, Available for sale, Gross Unrealized, Gains	308	638
Fixed maturities, Available for sale, Gross Unrealized, Losses	(179)	(38)
Fixed maturities, Available for sale, Net Unrealized, Gains (Losses)	129	600
Available for sale (AFS) fixed maturities	$ 19,074	$ 18,736

Investments - Equity securities

Investments - Equity securities reported at fair value (Details) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Debt Securities, Trading, and Equity Securities, FV-NI [Line Items]
Equity securities, at fair value	$ 1,786	$ 1,662
Common stocks
Debt Securities, Trading, and Equity Securities, FV-NI [Line Items]
Equity securities, at cost	1,099
Equity securities, at fair value	1,154
Equity securities, fair value in excess of cost	55
Perpetual preferred stocks
Debt Securities, Trading, and Equity Securities, FV-NI [Line Items]
Equity securities, at cost	632
Equity securities, at fair value	632
Equity securities, fair value in excess of cost	0
Equity securities
Debt Securities, Trading, and Equity Securities, FV-NI [Line Items]
Equity securities, at cost	1,731
Equity securities, at fair value	1,786
Equity securities, fair value in excess of cost	$ 55

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	Mar. 31, 2018	Dec. 31, 2017
Total fixed maturities
Available for sale securities in a continuous unrealized loss position
Unrealized Loss - Less than twelve months	$ (203)	$ (37)
Fair Value - Less than twelve months	$ 12,065	$ 4,295
Fair Value as % of Cost - Less than twelve months	98.00%	99.00%
Unrealized Loss - Twelve months or more	$ (60)	$ (45)
Fair Value - Twelve months or more	$ 1,551	$ 1,574
Fair Value as % of Cost - Twelve months or more	96.00%	97.00%
U.S. Government and government agencies
Available for sale securities in a continuous unrealized loss position
Unrealized Loss - Less than twelve months	$ (1)	$ 0
Fair Value - Less than twelve months	$ 57	$ 55
Fair Value as % of Cost - Less than twelve months	98.00%	100.00%
Unrealized Loss - Twelve months or more	$ (3)	$ (3)
Fair Value - Twelve months or more	$ 119	$ 123
Fair Value as % of Cost - Twelve months or more	98.00%	98.00%
States, municipalities and political subdivisions
Available for sale securities in a continuous unrealized loss position
Unrealized Loss - Less than twelve months	$ (26)	$ (8)
Fair Value - Less than twelve months	$ 1,745	$ 825
Fair Value as % of Cost - Less than twelve months	99.00%	99.00%
Unrealized Loss - Twelve months or more	$ (13)	$ (10)
Fair Value - Twelve months or more	$ 411	$ 431
Fair Value as % of Cost - Twelve months or more	97.00%	98.00%
Foreign government
Available for sale securities in a continuous unrealized loss position
Unrealized Loss - Less than twelve months	$ 0	$ 0
Fair Value - Less than twelve months	$ 22	$ 4
Fair Value as % of Cost - Less than twelve months	100.00%	100.00%
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%
Residential MBS
Available for sale securities in a continuous unrealized loss position
Unrealized Loss - Less than twelve months	$ (3)	$ (1)
Fair Value - Less than twelve months	$ 155	$ 118
Fair Value as % of Cost - Less than twelve months	98.00%	99.00%
Unrealized Loss - Twelve months or more	$ (4)	$ (5)
Fair Value - Twelve months or more	$ 114	$ 118
Fair Value as % of Cost - Twelve months or more	97.00%	96.00%
Commercial MBS
Available for sale securities in a continuous unrealized loss position
Unrealized Loss - Less than twelve months	$ (3)	$ (1)
Fair Value - Less than twelve months	$ 148	$ 67
Fair Value as % of Cost - Less than twelve months	98.00%	99.00%
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	$ (21)	$ (7)
Fair Value - Less than twelve months	$ 2,586	$ 1,195
Fair Value as % of Cost - Less than twelve months	99.00%	99.00%
Unrealized Loss - Twelve months or more	$ (10)	$ (9)
Fair Value - Twelve months or more	$ 306	$ 299
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	$ (149)	$ (20)
Fair Value - Less than twelve months	$ 7,352	$ 2,031
Fair Value as % of Cost - Less than twelve months	98.00%	99.00%
Unrealized Loss - Twelve months or more	$ (30)	$ (18)
Fair Value - Twelve months or more	$ 601	$ 603
Fair Value as % of Cost - Twelve months or more	95.00%	97.00%
Total equity securities
Available for sale securities in a continuous unrealized loss position
Unrealized Loss - Less than twelve months		$ (22)
Fair Value - Less than twelve months		$ 158
Fair Value as % of Cost - Less than twelve months		88.00%
Unrealized Loss - Twelve months or more		$ (1)
Fair Value - Twelve months or more		$ 13
Fair Value as % of Cost - Twelve months or more		93.00%
Common stocks
Available for sale securities in a continuous unrealized loss position
Unrealized Loss - Less than twelve months		$ (22)
Fair Value - Less than twelve months		$ 117
Fair Value as % of Cost - Less than twelve months		84.00%
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%
Perpetual preferred stocks
Available for sale securities in a continuous unrealized loss position
Unrealized Loss - Less than twelve months		$ 0
Fair Value - Less than twelve months		$ 41
Fair Value as % of Cost - Less than twelve months		100.00%
Unrealized Loss - Twelve months or more		$ (1)
Fair Value - Twelve months or more		$ 13
Fair Value as % of Cost - Twelve months or more		93.00%

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	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Roll Forward]
Beginning Balance	$ 145	$ 153
Additional credit impairments on:
Previously impaired securities	0	0
Securities without prior impairments	0	0
Reductions due to sales or redemptions	(1)	(7)
Ending Balance	$ 144	$ 146

Investments - Scheduled maturit

Investments - Scheduled maturities of available for sale fixed maturities (Details) $ in Millions	3 Months Ended
	Mar. 31, 2018USD ($)
Fair Value Percent, Fiscal Year Maturity [Abstract]
Average life of ABS	4 years 6 months
Average life of MBS	4 years 6 months
Fixed maturities
Amortized Cost Basis, Fiscal Year Maturity [Abstract]
One year or less	$ 793
After one year through five years	7,314
After five years through ten years	13,345
After ten years	4,731
Fixed maturities amortized cost, Subtotal	26,183
ABS (average life of approximately 4-1/2 years)	8,546
MBS (average life of approximately 4-1/2 years)	3,654
Amortized Cost	38,383
Fair Value, Fiscal Year Maturity [Abstract]
One year or less	804
After one year through five years	7,431
After five years through ten years	13,425
After ten years	4,799
Fixed maturities fair value, Subtotal	26,459
ABS (average life of approximately 4-1/2 years)	8,663
MBS (average life of approximately 4-1/2 years)	4,003
Fair Value	$ 39,125
Fair Value Percent, Fiscal Year Maturity [Abstract]
One year or less	2.00%
After one year through five years	19.00%
After five years through ten years	35.00%
After ten years	12.00%
Fixed maturities fair value, Subtotal, Percent	68.00%
ABS (average life of approximately 4-1/2 years)	22.00%
MBS (average life of approximately 4-1/2 years)	10.00%
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		Mar. 31, 2018	Dec. 31, 2017
Unrealized gain on:
Pretax		$ 433	$ 1,063
Deferred Tax		(91)	(223)
Net		342	840
Total investments
Unrealized gain on:
Pretax			1,620
Deferred Tax			(340)
Net			1,280
Total fixed maturities
Unrealized gain on:
Pretax		742	1,341
Deferred Tax		(156)	(282)
Net		586	1,059
Fixed maturities — annuity segment
Unrealized gain on:
Pretax	[1]	594	1,082
Deferred Tax	[1]	(125)	(227)
Net	[1]	469	855
Fixed maturities — all other
Unrealized gain on:
Pretax		148	259
Deferred Tax		(31)	(55)
Net		117	204
Equity securities
Unrealized gain on:
Pretax	[2]		279
Deferred Tax	[2]		(58)
Net	[2]		221
Deferred policy acquisition costs — annuity segment
Unrealized gain on:
Pretax		(236)	(433)
Deferred Tax		49	91
Net		(187)	(342)
Annuity benefits accumulated
Unrealized gain on:
Pretax		(79)	(137)
Deferred Tax		17	29
Net		(62)	(108)
Unearned revenue
Unrealized gain on:
Pretax		6	13
Deferred Tax		(1)	(3)
Net		$ 5	$ 10
[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 other than those accounted for under the equity method are carried at fair value through net earnings.

Investments - Schedule of sourc

Investments - Schedule of sources of net investment income (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Net Investment Income [Line Items]
Investment income	$ 500	$ 440
Investment expenses	(5)	(5)
Net investment income	495	435
Fixed maturities
Net Investment Income [Line Items]
Investment income	412	389
Equity securities
Net Investment Income [Line Items]
Investment income	19	21
Equity in earnings of partnerships and similar investments
Net Investment Income [Line Items]
Investment income	46	10
Other
Net Investment Income [Line Items]
Investment income	$ 23	$ 20

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		3 Months Ended
		Mar. 31, 2018	Mar. 31, 2017
Realized gains (losses) and changes in unrealized appreciation (depreciation) related to fixed maturity and equity security investments
Realized before impairments		$ (92)	$ 9
Realized — impairments		(1)	(6)
Realized gains (losses) on securities		(93)	3
Net of tax
Realized gains (losses) and changes in unrealized appreciation (depreciation) related to fixed maturity and equity security investments
Realized before impairments		(72)	6
Realized — impairments		(1)	(4)
Realized gains (losses) on securities		(73)	2
Change in unrealized		(277)	125
Total pretax
Realized gains (losses) and changes in unrealized appreciation (depreciation) related to fixed maturity and equity security investments
Realized before impairments		(92)	9
Realized — impairments		(1)	(6)
Realized gains (losses) on securities		(93)	3
Change in unrealized		(351)	191
Fixed maturities
Realized gains (losses) and changes in unrealized appreciation (depreciation) related to fixed maturity and equity security investments
Realized before impairments		(1)	5
Realized — impairments		(1)	0
Realized gains (losses) on securities		(2)	5
Change in unrealized		(599)	202
Equity securities
Realized gains (losses) and changes in unrealized appreciation (depreciation) related to fixed maturity and equity security investments
Realized before impairments	[1]	(95)	2
Realized — impairments	[1]	0	(9)
Realized gains (losses) on securities	[1]	(95)	(7)
Change in unrealized	[1]	0	72
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		0	3
Realized — impairments		0	0
Realized gains (losses) on securities		0	3
Change in unrealized		0	0
Other, Including DPAC and reserves related to the annuity business
Realized gains (losses) and changes in unrealized appreciation (depreciation) related to fixed maturity and equity security investments
Realized before impairments	[2]	4	(1)
Realized — impairments	[2]	0	3
Realized gains (losses) on securities	[2]	4	2
Change in unrealized	[2]	248	(83)
Tax effects
Realized gains (losses) and changes in unrealized appreciation (depreciation) related to fixed maturity and equity security investments
Realized before impairments		20	(3)
Realized — impairments		0	2
Realized gains (losses) on securities		20	(1)
Change in unrealized		$ 74	$ (66)
[1]	As discussed in Note A — “Accounting Policies — Investments,” effective January 1, 2018, all equity securities other than those accounted for under the equity method are carried at fair value through net earnings. AFG recorded a net realized loss of $94 million on equity securities during the first three months of 2018 on securities that were still owned at March 31, 2018.
[2]	Primarily adjustments to deferred policy acquisition costs and reserves related to the annuity business.

Investments - Gross realized ga

Investments - Gross realized gains and losses on available for sale fixed maturity and equity security investment transactions (Details) - Fixed maturities - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Gross realized gains and losses on the sale of available for sale fixed maturity and equity security investments
Gross gains	$ 6	$ 5
Gross losses	$ (3)	$ 0

Derivatives - Narrative (Detail

Derivatives - Narrative (Details)	3 Months Ended
	Mar. 31, 2018USD ($)swap	Mar. 31, 2017USD ($)	Dec. 31, 2017USD ($)
Derivative Instruments, Gain (Loss) [Line Items]
Carrying value of collateral received to support purchased call options	$ 356,000,000		$ 389,000,000
Cash Flow Hedges | Designated as Hedging Instrument | Interest rate swaps
Derivative Instruments, Gain (Loss) [Line Items]
Number of interest rate swaps designated and qualifying as a cash flow hedges | swap	11
Notional amount of derivative instrument outstanding	$ 1,680,000,000		1,580,000,000
Gain (loss) reclassified from AOCI into net investment income	1,000,000	$ 2,000,000
Gain (loss) on cash flow hedge ineffectiveness recorded in Net Earnings	0	$ 0
Collateral receivable supporting interest rate swaps	107,000,000		70,000,000
Other assets | Cash Flow Hedges | Designated as Hedging Instrument | Interest rate swaps
Derivative Instruments, Gain (Loss) [Line Items]
Net derivatives, at fair value	0
Other assets | Maximum | Cash Flow Hedges | Designated as Hedging Instrument | Interest rate swaps
Derivative Instruments, Gain (Loss) [Line Items]
Net derivatives, at fair value			1,000,000
Other liabilities | Cash Flow Hedges | Designated as Hedging Instrument | Interest rate swaps
Derivative Instruments, Gain (Loss) [Line Items]
Net derivatives, at fair value	(61,000,000)		$ (31,000,000)
New interest rate swaps entered into during the period | Cash Flow Hedges | Designated as Hedging Instrument | Interest rate swaps
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount of derivative instrument outstanding	$ 130,000,000
Number of interest rate swaps entered into during the period | swap	1

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	Mar. 31, 2018	Dec. 31, 2017
Derivatives included in AFG' s Balance Sheet at fair value
Derivative asset, at fair value	$ 705	$ 810
Derivative liability, at fair value	2,552	2,546
MBS with embedded derivatives | Fixed maturities
Derivatives included in AFG' s Balance Sheet at fair value
Derivative asset, at fair value	111	105
Public company warrants | Equity securities
Derivatives included in AFG' s Balance Sheet at fair value
Derivative asset, at fair value	3	4
Fixed-indexed annuities (embedded derivative) | Annuity benefits accumulated
Derivatives included in AFG' s Balance Sheet at fair value
Derivative liability, at fair value	2,549	2,542
Equity index call options | Equity index call options
Derivatives included in AFG' s Balance Sheet at fair value
Derivative asset, at fair value	591	701
Reinsurance contracts (embedded derivative) | Other liabilities
Derivatives included in AFG' s Balance Sheet at fair value
Derivative liability, at fair value	$ 3	$ 4

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	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Derivative, Gain (Loss) on Derivative, Net [Abstract]
Derivative	$ 21	$ (7)
MBS with embedded derivatives | Realized gains on securities
Derivative, Gain (Loss) on Derivative, Net [Abstract]
Derivative	(4)	0
Public company warrants | Realized gains on securities
Derivative, Gain (Loss) on Derivative, Net [Abstract]
Derivative	(1)	0
Fixed-indexed annuities (embedded derivative) | Annuity benefits
Derivative, Gain (Loss) on Derivative, Net [Abstract]
Derivative	63	(147)
Equity index call options | Annuity benefits
Derivative, Gain (Loss) on Derivative, Net [Abstract]
Derivative	(38)	141
Reinsurance contracts (embedded derivative) | Net investment income
Derivative, Gain (Loss) on Derivative, Net [Abstract]
Derivative	$ 1	$ (1)

Deferred Policy Acquisition C56

Deferred Policy Acquisition Costs - Narrative (Details) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Deferred Policy Acquisition Costs Disclosures [Abstract]
Accumulated amortization of present value of future profits	$ 143	$ 141

Deferred Policy Acquisition C57

Deferred Policy Acquisition Costs - Progression of deferred policy acquisition costs (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
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	$ 1,216	$ 1,239
Deferred policy acquisition costs and present value of future profits, additions	219	207
Deferred policy acquisition costs and present value of future profits, periodic amortization	(230)	(185)
Deferred policy acquisition costs and present value of future profits, change included in realized gains	3	2
Deferred policy acquisition costs and present value of future profits, foreign currency translation	1	1
Deferred policy acquisition costs and present value of future profits, change in unrealized	208	(59)
Deferred policy acquisition costs and present value of future profits, ending balance	1,417	1,205
P&C
Movement Analysis of Deferred Policy Acquisition Costs [Roll Forward]
Deferred policy acquisition costs, beginning balance	270	238
Deferred policy acquisition costs, additions	162	139
Deferred policy acquisition costs, periodic amortization	(154)	(135)
Deferred policy acquisition costs, foreign currency translation	1	1
Deferred policy acquisition costs, ending balance	279	243
Annuity and Other
Movement Analysis of Deferred Policy Acquisition Costs [Roll Forward]
Deferred policy acquisition costs, beginning balance	1,217	1,110
Deferred policy acquisition costs, additions	57	67
Deferred policy acquisition costs, periodic amortization	(69)	(42)
Deferred policy acquisition costs, change included in realized gains	3	2
Deferred policy acquisition costs, ending balance	1,208	1,137
Movement in Deferred Sales Inducements [Roll Forward]
Deferred sales inducements, beginning balance	102	110
Deferred sales inducements, additions	0	1
Deferred sales inducements, periodic amortization	(5)	(6)
Deferred sales inducements, change included in realized gains	0	0
Deferred sales inducements, ending balance	97	105
Movement in Present Value of Future Insurance Profits [Roll Forward]
Present value of future profits, beginning balance	49	46
Present value of future profits, periodic amortization	(2)	(2)
Present value of future profits, ending balance	47	44
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	(422)	(265)
Unrealized investment gains (losses), change in unrealized	208	(59)
Unrealized investment gains (losses), ending balance	(214)	(324)
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	946	1,001
Deferred policy acquisition costs and present value of future profits, additions	57	68
Deferred policy acquisition costs and present value of future profits, periodic amortization	(76)	(50)
Deferred policy acquisition costs and present value of future profits, change included in realized gains	3	2
Deferred policy acquisition costs and present value of future profits, change in unrealized	208	(59)
Deferred policy acquisition costs and present value of future profits, ending balance	1,138	962
Excluding Unrealized Gains | Annuity and Other
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	1,368	1,266
Deferred policy acquisition costs and present value of future profits, change in unrealized	0	0
Deferred policy acquisition costs and present value of future profits, ending balance	$ 1,352	$ 1,286

Managed Investment Entities - N

Managed Investment Entities - Narrative (Details) $ in Millions	1 Months Ended		3 Months Ended
	Mar. 31, 2018USD ($)	Mar. 31, 2017USD ($)	Mar. 31, 2018USD ($)collateralizedloanobligation	Mar. 31, 2017USD ($)	Dec. 31, 2017USD ($)
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			16
Proceeds received by subsidiaries related to sales and redemptions of managed investment entities liabilities			$ 17	$ 4
Number of collateralized loan obligation entities substantially liquidated, during the period | collateralizedloanobligation			1
Difference between aggregate unpaid principal balance and fair value of CLOs' fixed maturity investments	$ 38		$ 38		$ 55
Difference between aggregate unpaid principal balance and carrying value of CLOs' debt	143		143		118
Carrying amount of CLO loans in default	1		1		1
Aggregate unpaid principal balance of CLO loans in default	8		8		8
Variable interest entity, primary beneficiary
Variable Interest Entity [Line Items]
Aggregate fair value of investment in collateralized loan obligations	221	$ 230	221	$ 230	$ 215
New Collateralized Loan Obligation Entities
Variable Interest Entity [Line Items]
Face value of liabilities issued by managed investment entities on issuance date	463	408
Face amount of managed investment entities liabilities purchased by subsidiaries at issuance date	31	$ 24
Subordinated Debt Obligations | Variable interest entity, primary beneficiary
Variable Interest Entity [Line Items]
Aggregate fair value of investment in collateralized loan obligations	$ 136		$ 136

Managed Investment Entities - S

Managed Investment Entities - Selected financial information related to CLOs (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Gains (losses) on change in fair value of assets/liabilities:
Assets	[1]	$ 14	$ 5
Liabilities	[1]	(17)	(5)
Management fees paid to AFG		4	4
CLO earnings (losses) attributable to AFG shareholders	[2]	3	6
Variable interest entity, primary beneficiary
Variable Interest Entity [Line Items]
Investment in CLO tranches at end of period		$ 221	$ 230	$ 215
[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 Intangibles

Goodwill and Other Intangibles - Narrative (Details) - USD ($)	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Goodwill and Intangible Assets Disclosure [Abstract]
Changes in the goodwill balance during the period	$ 0
Goodwill	199,000,000		$ 199,000,000
Amortizable intangible assets related to property and casualty insurance acquisitions	36,000,000		26,000,000
Accumulated amortization	32,000,000		$ 30,000,000
Amortization of intangible assets	$ 2,000,000	$ 2,000,000

Long-Term Debt - Narrative (Det

Long-Term Debt - Narrative (Details) - USD ($)	3 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Long-term Debt, Fiscal Year Maturity [Abstract]
Scheduled principal payments on debt in next year	$ 0
Scheduled principal payments on debt in year two	0
Scheduled principal payments on debt in year three	0
Scheduled principal payments on debt in year four	0
Scheduled principal payments on debt in year five	0
Scheduled principal payments on debt in year six	0
AFG
Long-term Debt, Fiscal Year Maturity [Abstract]
Revolving credit line	500,000,000
Amount borrowed under revolving credit facility	$ 0	$ 0
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%
Senior Notes | 4.50% Senior Notes due June 2047 | AFG
Long-term Debt, Fiscal Year Maturity [Abstract]
Interest rate on debt instruments	4.50%
Senior Notes | 3.50% Senior Notes due August 2026 | AFG
Long-term Debt, Fiscal Year Maturity [Abstract]
Interest rate on debt instruments	3.50%
Subordinated Debentures | 6-1/4% Subordinated Debentures due September 2054 | AFG
Long-term Debt, Fiscal Year Maturity [Abstract]
Interest rate on debt instruments	6.25%
Subordinated Debentures | 6% Subordinated Debentures due November 2055 | AFG
Long-term Debt, Fiscal Year Maturity [Abstract]
Interest rate on debt instruments	6.00%

Long-Term Debt - Schedule of lo

Long-Term Debt - Schedule of long-term debt (Details) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Summary of Carrying value of long-term debt
Principal	$ 1,318	$ 1,318
Discount and Issue Costs	(17)	(17)
Carrying Value	1,301	1,301
Senior Notes | AFG
Summary of Carrying value of long-term debt
Principal	1,018	1,018
Discount and Issue Costs	(7)	(7)
Carrying Value	1,011	1,011
Senior Notes | 4.50% Senior Notes due June 2047 | AFG
Summary of Carrying value of long-term debt
Principal	590	590
Discount and Issue Costs	(2)	(2)
Carrying Value	588	588
Senior Notes | 3.50% Senior Notes due August 2026 | AFG
Summary of Carrying value of long-term debt
Principal	425	425
Discount and Issue Costs	(5)	(5)
Carrying Value	420	420
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 - Preferre

Shareholders' Equity - Preferred stock authorized for issuance (Details)	Mar. 31, 2018$ / sharesshares
Voting Preferred Stock
Class of Stock [Line Items]
Preferred Stock, shares authorized | shares	12,500,000
Preferred Stock, par value (in USD per share) | $ / shares	$ 0
Nonvoting Preferred Stock
Class of Stock [Line Items]
Preferred Stock, shares authorized | shares	12,500,000
Preferred Stock, par value (in USD per share) | $ / shares	$ 0

Shareholders' Equity - Narrativ

Shareholders' Equity - Narrative (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Jan. 01, 2018	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Net of tax unrealized gains (losses) related to credit-only impaired securities	$ 68			$ 68
Cumulative effect of accounting change				$ 4
Compensation expense related to stock incentive plans	$ 5	$ 11
Stock Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted Common Stock, shares issued (shares)	200,625
Restricted Common Stock, fair value per share (USD per share)	$ 112.86
Common Stock options issued under stock incentive plan (shares)	0
Annual Equity Bonus Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Other benefit plans, shares issued (shares)	45,804
Common Stock issued, fair value per share (USD per share)	$ 115.49
Accounting Standards Update 2016-01 | Equity securities
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Cumulative effect of accounting change			$ (221)

Shareholders' Equity - Progress

Shareholders' Equity - Progression of the components of accumulated other comprehensive income (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2018		Mar. 31, 2017		Jan. 01, 2018		Dec. 31, 2017
Accumulated Other Comprehensive Income (Loss) [Line Items]
Net of tax unrealized gains (losses) related to credit-only impaired securities		$ 68						$ 68
Accumulated Other Comprehensive Income [Roll Forward]
AOCI beginning balance		813
Other comprehensive income (loss), net of tax		(287)		$ 124
Cumulative effect of accounting change								4
AOCI ending balance		305
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		(353)		191
Other comprehensive income (loss), unrealized holding gains on securities arising during the period, tax		74		(66)
Other comprehensive income (loss), unrealized holding gains on securities arising during the period, net of tax		(279)		125
Reclassification from accumulated other comprehensive income, pretax	[1]	2		0
Reclassification from accumulated other comprehensive income, tax	[1]	0		0
Reclassification from accumulated other comprehensive income, net of tax		2		0
Accumulated Other Comprehensive Income [Roll Forward]
Other comprehensive income (loss), pretax		(351)		191
Other comprehensive income (loss), tax		74		(66)
Other comprehensive income (loss), net of tax		(277)		125
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		0
Reclassification from accumulated other comprehensive income, net of tax	[1]	0		0
Accumulated Other Comprehensive Income [Roll Forward]
Other comprehensive income (loss), net of tax		0		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		(279)		125
Reclassification from accumulated other comprehensive income, net of tax		2		0
Accumulated Other Comprehensive Income [Roll Forward]
AOCI beginning balance		840	[2]	404
Other comprehensive income (loss), net of tax		(277)		125
Cumulative effect of accounting change	[3]			0		$ (221)
AOCI ending balance		342	[2]	529
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		(14)		(2)
Other comprehensive income (loss), tax		3		1
Other comprehensive income (loss), net of tax		(11)		(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
Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent
Accumulated Other Comprehensive Income [Roll Forward]
AOCI beginning balance		(13)		(7)
Other comprehensive income (loss), net of tax		(11)		(1)
Cumulative effect of accounting change	[3]			0		0
AOCI ending balance		(24)		(8)
Accumulated Foreign Currency Adjustment Including Portion Attributable to Noncontrolling Interest
Accumulated Other Comprehensive Income [Roll Forward]
Other comprehensive income (loss), pretax		2		0
Other comprehensive income (loss), tax		(1)		0
Other comprehensive income (loss), net of tax		1		0
Accumulated Foreign Currency Adjustment Attributable to Noncontrolling Interest
Accumulated Other Comprehensive Income [Roll Forward]
Other comprehensive income (loss), net of tax		0		0
Accumulated Foreign Currency Adjustment Attributable to Parent
Accumulated Other Comprehensive Income [Roll Forward]
AOCI beginning balance		(6)		(15)
Other comprehensive income (loss), net of tax		1		0
Cumulative effect of accounting change	[3]			0		0
AOCI ending balance		(5)		(15)
Accumulated Defined Benefit Plans Adjustment Including Portion Attributable to Noncontrolling Interest
Accumulated Other Comprehensive Income [Roll Forward]
Other comprehensive income (loss), pretax		0		0
Other comprehensive income (loss), tax		0		0
Other comprehensive income (loss), net of tax		0		0
Accumulated Defined Benefit Plans Adjustment Attributable to Noncontrolling Interest
Accumulated Other Comprehensive Income [Roll Forward]
Other comprehensive income (loss), net of tax		0		0
Accumulated Defined Benefit Plans Adjustment Attributable to Parent
Accumulated Other Comprehensive Income [Roll Forward]
AOCI beginning balance		(8)		(7)
Other comprehensive income (loss), net of tax		0		0
Cumulative effect of accounting change	[3]			0		0
AOCI ending balance		(8)		(7)
AOCI Including Portion Attributable to Noncontrolling Interest
Accumulated Other Comprehensive Income [Roll Forward]
Other comprehensive income (loss), pretax		(363)		189
Other comprehensive income (loss), tax		76		(65)
Other comprehensive income (loss), net of tax		(287)		124
AOCI Attributable to Noncontrolling Interest
Accumulated Other Comprehensive Income [Roll Forward]
Other comprehensive income (loss), net of tax		0		0
AOCI Attributable to Parent
Accumulated Other Comprehensive Income [Roll Forward]
AOCI beginning balance		813		375
Other comprehensive income (loss), net of tax		(287)		124
Cumulative effect of accounting change				0	[3]	$ (221)	[3]	$ (221)
AOCI ending balance		$ 305		$ 499
[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
[2]	Includes net unrealized gains of $68 million at both March 31, 2018 and December 31, 2017 related to securities for which only the credit portion of an other-than-temporary impairment has been recorded in earnings.
[3]	On January 1, 2018, AFG adopted new guidance that requires all equity securities other than those accounted for under the equity method to be reported at fair value with holding gains and losses recognized in net earnings. At the date of adoption, the $221 million net unrealized gain on equity securities classified as available for sale (with unrealized holding gains and losses reported in AOCI) under the prior guidance was reclassified from AOCI to retained earnings as the cumulative effect of an accounting change.

Income Taxes - Narrative (Detai

Income Taxes - Narrative (Details) - USD ($) $ in Millions	Jan. 01, 2018	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017
Income Tax Reconciliation [Line Items]
Statutory rate of income taxes		21.00%		35.00%
Operating loss carryforwards subject to SRLY tax rules will expire unutilized at December 31, 2018		$ 19
Tax Cuts and Jobs Act of 2017
Income Tax Reconciliation [Line Items]
Statutory rate of income taxes	21.00%
Decrease in net deferred tax asset resulting from the changes in the Tax Cuts and Jobs Act of 2017			$ 83

Income Taxes - Reconciliation o

Income Taxes - Reconciliation of income taxes at the statutory rate to the provision for income taxes (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Effective Income Tax Rate Reconciliation, Amount [Abstract]
Earnings before income taxes (“EBT”)	$ 174	$ 223
Income taxes at statutory rate	37	78
Effect of stock-based compensation	(5)	(6)
Effect of tax exempt interest	(3)	(6)
Effect of dividends received deduction	(1)	(2)
Effect of foreign operations	3	6
Effect of nondeductible expenses	2	2
Effect of change in valuation allowance	0	(2)
Effect of other income tax reconciliation	0	(2)
Provision for income taxes as shown on the Statement of Earnings	$ 33	$ 68
Effective Income Tax Rate Reconciliation, Percent [Abstract]
Income taxes at statutory rate as a percentage of EBT	21.00%	35.00%
Effect of stock-based compensation as a percentage of EBT	(3.00%)	(3.00%)
Effect of tax exempt interest as a percentage of EBT	(2.00%)	(3.00%)
Effect of dividends received deduction as a percentage of EBT	(0.00%)	(1.00%)
Effect of foreign operations as a percentage of EBT	2.00%	3.00%
Effect of nondeductible expenses as a percentage of EBT	1.00%	1.00%
Effect of change in valuation allowance as a percentage of EBT	0.00%	(1.00%)
Effect of other income tax reconciliation as a percentage of EBT	0.00%	(1.00%)
Provision for income taxes as shown on the Statement of Earnings as a percentage of EBT	19.00%	30.00%

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
		Mar. 31, 2018	Mar. 31, 2017
Analysis of changes in the liability for losses and loss adjustment expenses, net of reinsurance
Balance at beginning of year		$ 9,678	$ 8,563
Less reinsurance recoverables, net of allowance		2,957	2,302
Net liability at beginning of year		6,721	6,261
Liability for losses and loss adjustment expenses, period increase (decrease) [Abstract]
Provision for losses and LAE occurring in the current period		697	637
Total losses and LAE incurred		641	609
Payments for losses and LAE of:
Current year		(86)	(84)
Prior years		(554)	(470)
Total payments		(640)	(554)
Reserves of business disposed	[1]	(319)	0
Foreign currency translation and other		2	8
Net liability at end of period		6,405	6,324
Add back reinsurance recoverables, net of allowance		2,788	2,297
Gross unpaid losses and LAE included in the balance sheet at end of period		9,193	8,621
Net decrease in the provision for claims of prior years
Liability for losses and loss adjustment expenses, period increase (decrease) [Abstract]
Net decrease in the provision for claims of prior years		$ (56)	$ (28)
[1]	Reflects the reinsurance to close transaction at Neon discussed below.