SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies)

6 Months Ended

Jun. 30, 2018

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Description of Business and Basis of Presentation

Description of Business

Aflac Incorporated (the Parent Company) and its subsidiaries (collectively, the Company) primarily sell supplemental health and life insurance in the United States and Japan. The Company's insurance business is marketed and administered through American Family Life Assurance Company of Columbus (Aflac) in the United States (Aflac U.S.) and, effective April 1, 2018, through Aflac Life Insurance Japan Ltd. in Japan (Aflac Japan). Prior to April 1, 2018, the Company's insurance business was marketed in Japan as a branch of Aflac. American Family Life Assurance Company of New York (Aflac New York) is a wholly owned subsidiary of Aflac. Most of Aflac's policies are individually underwritten and marketed through independent agents. Additionally, Aflac U.S. markets and administers group products through Continental American Insurance Company (CAIC), branded as Aflac Group Insurance. The Company's insurance operations in the United States and Japan service the two markets for the Company's insurance business. Aflac Japan's revenues, including realized gains and losses on its investment portfolio, accounted for 70% and 69% of the Company's total revenues in the six-month periods ended June 30, 2018 and 2017, respectively. The percentage of the Company's total assets attributable to Aflac Japan was 85% at June 30, 2018, compared with 83% at December 31, 2017.

Basis of Presentation

The Company prepares its financial statements in accordance with U.S. generally accepted accounting principles (GAAP). These principles are established primarily by the Financial Accounting Standards Board (FASB). In these Notes to the Consolidated Financial Statements, references to U.S. GAAP issued by the FASB are derived from the FASB Accounting Standards Codification^TM (ASC). The preparation of financial statements in conformity with U.S. GAAP requires the Company to make estimates based on currently available information when recording transactions resulting from business operations. The most significant items on the Company's balance sheet that involve a greater degree of accounting estimates and actuarial determinations subject to changes in the future are the valuation of investments and derivatives, deferred policy acquisition costs (DAC), liabilities for future policy benefits and unpaid policy claims, and income taxes. These accounting estimates and actuarial determinations are sensitive to market conditions, investment yields, mortality, morbidity, commission and other acquisition expenses, and terminations by policyholders. As additional information becomes available, or actual amounts are determinable, the recorded estimates will be revised and reflected in operating results. Although some variability is inherent in these estimates, the Company believes the amounts provided are adequate.

The unaudited consolidated financial statements include the accounts of the Parent Company, its subsidiaries and those entities required to be consolidated under applicable accounting standards. All material intercompany accounts and transactions have been eliminated.

In the opinion of management, the accompanying unaudited consolidated financial statements of the Company contain all adjustments, consisting of normal recurring accruals, which are necessary to fairly present the consolidated balance sheets as of June 30, 2018, and December 31, 2017, the consolidated statements of earnings and comprehensive income (loss) for the three- and six-month periods ended June 30, 2018 and 2017, and the consolidated statements of shareholders' equity and cash flows for the six-month periods ended June 30, 2018 and 2017. Results of operations for interim periods are not necessarily indicative of results for the entire year. As a result, these financial statements should be read in conjunction with the financial statements and notes thereto included in the Company's annual report on Form 10-K for the year ended December 31, 2017 (2017 Annual Report).

Stock split: On February 13, 2018, the Board of Directors of the Parent Company declared a two-for-one stock split of the Company’s common stock in the form of a 100% stock dividend payable on March 16, 2018 to shareholders of record at the close of business on March 2, 2018. The stock split was payable in the form of one additional common stock share for every share of common stock held. All equity and share-based data, including the number of shares outstanding and per share amounts, have been adjusted to reflect the stock split for all periods presented in this Quarterly Report on Form 10-Q.

Reclassifications

Reclassifications: Certain reclassifications have been made to prior-year amounts to conform to current-year reporting classifications. These reclassifications had no impact on net earnings or total shareholders' equity.

Perpetual securities have been reclassified in prior periods from a separate line item to fixed maturity securities to conform to current period reporting classifications. This reclassification had no impact on net earnings or total shareholder’s equity.

Recently Adopted Accounting Pronouncements

Recently Adopted Accounting Pronouncements

Standard	Description	Date of Adoption	Effect on Financial Statements or Other Significant Matters
Accounting Standards Update (ASU) 2018-03 Technical Corrections and Improvements to Financial Instruments - Overall	In February 2018, the FASB issued amendments to clarify certain aspects of the guidance issued in the original Financial Instruments - Overall - Recognition and Measurement pronouncement summarized below. Specifically, for entities who have chosen the measurement alternative approach for equity securities without readily determinable fair values, the amendments clarify that entities may change from a measurement alternative approach to a fair value method through an irrevocable election that would apply to a specific equity security and all identical or similar investments of the same issuer; entities should use an observable price at the date of the transaction rather than reporting date for the measurement alternative calculation; and insurance companies should use a prospective transition method when applying the measurement alternative. The amendments are effective for public business entities for fiscal years beginning after December 15, 2017, and interim periods within those fiscal years beginning after June 15, 2018. All entities may early adopt these amendments for fiscal years beginning after December 15, 2017, including interim periods within those fiscal years, as long as they have adopted the Financial Instruments - Overall - Recognition and Measurement guidance discussed below.	Early adopted as of January 1, 2018	The adoption of this guidance did not have a significant impact on the Company’s financial position, results of operations, or disclosures.

Standard	Description	Date of Adoption	Effect on Financial Statements or Other Significant Matters
ASU 2018-02 Income Statement - Reporting Comprehensive Income: Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income	In February 2018, the FASB issued amendments which allow a reclassification from accumulated other comprehensive income (AOCI) to retained earnings of the effects of the change in the U.S. federal income tax rate resulting from the Tax Cuts and Jobs Act (Tax Act) on the gross deferred tax amounts and the corresponding valuation allowances related to items remaining in AOCI. The amendments eliminate the stranded tax effects resulting from the Tax Act and also require certain disclosures about the reclassified tax effects. The amendments are effective for all entities for fiscal years beginning after December 15, 2018, and interim periods within those fiscal years. Public business entities may early adopt this guidance in any interim reporting period for which financial statements have not yet been issued. The amendments should be applied either in the period of adoption or retrospectively to each period (or periods) in which the effect of the change in the U.S. federal corporate income tax rate in the Tax Act is recognized.	Early adopted as of January 1, 2018	The amounts reclassified from AOCI to retained earnings include the income tax effects of the change in the federal corporate tax rate enacted by the Tax Act. The Company’s policy is to follow the portfolio approach for releasing income tax effects from AOCI. The adoption of this guidance resulted in an increase to beginning 2018 AOCI of $374 million with a corresponding decrease to beginning 2018 retained earnings as of January 1, 2018.
ASU 2017-09 Compensation - Stock Compensation: Scope of Modification Accounting	In May 2017, the FASB issued amendments to provide guidance clarifying when changes to the terms or conditions of a share-based payment award must be accounted for as modifications. An entity should apply modification accounting if the fair value, vesting conditions or classification of the award (as an equity instrument or liability instrument) changes as a result of the change in terms or conditions of the award.	January 1, 2018	The adoption of this guidance did not have a significant impact on the Company's financial position, results of operations, or disclosures.
ASU 2017-07 Compensation - Retirement Benefits: Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost	In March 2017, the FASB issued amendments requiring that an employer report the service cost component of net periodic pension cost and net periodic postretirement benefit cost in the same line item or items as other compensation costs arising from services rendered by the pertinent employees during the period. The other components of net periodic pension cost and net periodic postretirement benefit cost are required to be presented in the income statement separately from the service cost component and outside a subtotal of income from operations, if one is presented. If a separate line item or items are used to present the other components of net benefit cost, that line item or items must be appropriately described. If a separate line item or items are not used, the line item or items used in the income statement to present the other components of net benefit cost must be disclosed. The amendments in this update also allow only the service cost component to be eligible for capitalization when applicable.	January 1, 2018	The adoption of this guidance did not have a significant impact on the Company's financial position, results of operations, or disclosures.

Standard	Description	Date of Adoption	Effect on Financial Statements or Other Significant Matters
ASU 2017-05 Other Income - Gains and Losses from the Derecognition of Nonfinancial Assets: Clarifying the Scope of Asset Derecognition Guidance and Accounting for Partial Sales of Nonfinancial Assets	In February 2017, the FASB issued amendments that clarify the scope and accounting guidance for the derecognition of a nonfinancial asset or a financial asset that meets the definition of an "in substance nonfinancial asset." The amendments define an "in substance nonfinancial asset" and provide additional accounting guidance for partial sales of nonfinancial assets.	January 1, 2018	The adoption of this guidance did not have a significant impact on the Company's financial position, results of operations, or disclosures.
ASU 2017-01 Business Combinations: Clarifying the Definition of a Business	In January 2017, the FASB issued amendments clarifying when a set of assets and activities is a business. The amendments provide a screen to exclude transactions where substantially all the fair value of the transferred set is concentrated in a single asset, or group of similar assets, from being evaluated as a business.	January 1, 2018	The adoption of this guidance did not have a significant impact on the Company's financial position, results of operations, or disclosures.
ASU 2016-18 Statement of Cash Flows: Restricted Cash	In November 2016, the FASB issued amendments requiring that a statement of cash flows explain the change during the period in the total of cash, cash equivalents, and amounts generally described as restricted cash or restricted cash equivalents.	January 1, 2018	The adoption of this guidance did not have a significant impact on the Company's financial position, results of operations, statements of cash flows, or disclosures.
ASU 2016-16 Income Taxes: Intra-Entity Transfers of Assets Other Than Inventory	In October 2016, the FASB issued amendments that require an entity to recognize the income tax consequences of an intra-entity transfer of an asset other than inventory when the transfer occurs.	January 1, 2018	The adoption of this guidance did not have a significant impact on the Company's financial position, results of operations, or disclosures.
ASU 2016-15 Statement of Cash Flows: Classification of Certain Cash Receipts and Cash Payments	In August 2016, the FASB issued amendments that provide guidance on eight specific statement of cash flows classification issues.	January 1, 2018	The adoption of this guidance did not have a significant impact on the Company's financial position, results of operations, statements of cash flows, or disclosures.
ASU 2016-01 Financial Instruments - Overall: Recognition and Measurement of Financial Assets and Financial Liabilities	In January 2016, the FASB issued guidance to address certain aspects of recognition, measurement, presentation, and disclosure of financial instruments. The main provisions of this guidance require certain equity investments to be measured at fair value with changes in fair value recognized in net earnings; separate presentation in other comprehensive income for changes in fair value of financial liabilities measured under the fair value option that are due to instrument-specific credit risk; and changes in disclosures associated with the fair value of financial instruments. The guidance also clarifies that entities should evaluate the need for a valuation allowance on a deferred tax asset (DTA) related to available-for-sale (AFS) securities in combination with the entity's other DTAs.	January 1, 2018	The Company recorded a cumulative effect adjustment with an increase to beginning 2018 retained earnings and a decrease to beginning 2018 AOCI of $148 million, net of taxes.

Standard	Description	Date of Adoption	Effect on Financial Statements or Other Significant Matters
ASU 2014-09 Revenue from Contracts with Customers	In May 2014, the FASB issued updated guidance that affects any entity that either enters into contracts with customers to transfer goods or services or enters into contracts for the transfer of nonfinancial assets unless those contracts are within the scope of other standards (e.g., insurance contracts or lease contracts). The core principle of the guidance is that an entity should recognize revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services.	January 1, 2018	The adoption of this guidance did not have a significant impact on the Company's financial position, results of operations, or disclosures.

Description of Accounting Pronouncements Pending Adoption

Accounting Pronouncements Pending Adoption

Standard	Description	Effect on Financial Statements or Other Significant Matters
ASU 2018-10 Codification Improvements to Topic 842, Leases	In July 2018, the FASB issued guidance which clarifies, corrects errors in, or makes minor improvements to the Codification related to ASU 2016-02, Leases (Topic 842). The amendments in this ASU affect narrow aspects of the guidance issued in the amendments to ASU 2016-02, including but not limited to, Residual Value Guarantees, Rate Implicit in the Lease, Lessee Reassessment of Lease Classification and Variable Lease Payments that Depend on an Index or a Rate. Amendments within this ASU follow the effective dates of Topic 842, which are effective for public business entities for fiscal years beginning after December 15, 2018, and interim periods within those fiscal years.	The adoption of this guidance is not expected to have a significant impact on the Company’s financial position, results of operations, or disclosures.
ASU 2018-01 Leases: Land Easement Practical Expedient for Transition to Topic 842	In January 2018, the FASB issued guidance which provides an entity with the option to elect a transition practical expedient to not evaluate, under Topic 842, land easements that exist or expired before the entity's adoption of Topic 842 and that were not previously accounted for as leases under Topic 840. The amendments clarify that new or modified land easements should be evaluated under the new leases standard once an entity has adopted the new standard. The amendments are effective for public business entities for fiscal years beginning after December 15, 2018, and interim periods within those fiscal years. Early adoption is permitted.	The adoption of this guidance is not expected to have a significant impact on the Company's financial position, results of operations, or disclosures.
ASU 2017-12 Derivatives and Hedging: Targeted Improvements to Accounting for Hedging Activities	In August 2017, the FASB issued guidance which improves and simplifies the accounting rules around hedge accounting and will create more transparency around how economic results are presented on financial statements. Issues addressed in this new guidance include: 1) risk component hedging, 2) accounting for the hedged item in fair value hedges of interest rate risk, 3) recognition and presentation of the effects of hedging instruments, and 4) amounts excluded from the assessment of hedge effectiveness. The amendments are effective for public business entities for fiscal years beginning after December 15, 2018, and interim periods within those fiscal years. Early adoption is permitted in any interim period after issuance of the guidance.	The adoption of this guidance is not expected to have a significant impact on the Company's financial position, results of operations, or disclosures.

Standard	Description	Effect on Financial Statements or Other Significant Matters
ASU 2017-08 Receivables - Nonrefundable Fees and Other Costs: Premium Amortization on Purchased Callable Debt Securities	In March 2017, the FASB issued amendments to shorten the amortization period for certain callable debt securities held at a premium. Specifically, the amendments require the premium to be amortized to the earliest call date. The amendments do not require an accounting change for securities held at a discount. The amendments are effective for public business entities for fiscal years beginning after December 15, 2018, and interim periods within those fiscal years. Early adoption is permitted, including adoption in an interim period.	The adoption of this guidance is not expected to have a significant impact on the Company's financial position, results of operations, or disclosures.
ASU 2017-04 Intangibles - Goodwill and Other: Simplifying the Test for Goodwill Impairment	In January 2017, the FASB issued amendments simplifying the subsequent measurement of goodwill. An entity, under this update, is no longer required to perform a hypothetical purchase price allocation to measure goodwill impairment. Instead, the entity should perform its annual or interim goodwill impairment test by comparing the fair value of a reporting unit with its carrying amount. The amendments are effective for public business entities that are SEC filers for annual or any interim goodwill impairment tests in fiscal years beginning after December 15, 2019. Early adoption is permitted for any goodwill impairment tests performed on testing dates after January 1, 2017.	The adoption of this guidance is not expected to have a significant impact on the Company's financial position, results of operations, or disclosures.
ASU 2016-13 Financial Instruments - Credit Losses: Measurement of Credit Losses on Financial Instruments	In June 2016, the FASB issued amendments that require a financial asset (or a group of financial assets) measured on an amortized cost basis to be presented net of an allowance for credit losses in order to reflect the amount expected to be collected on the financial asset(s). The measurement of expected credit losses is amended by replacing the incurred loss impairment methodology in current U.S. GAAP with a methodology that reflects expected credit losses and requires consideration of a broader range of reasonable and supportable information to inform about a credit loss. Credit losses on available-for-sale debt securities will continue to be measured in a manner similar to current U.S. GAAP; however, the amendments require that credit losses be presented as an allowance rather than as a write-down. Other amendments include changes to the balance sheet presentation and interest income recognition of purchased financial assets with a more-than-insignificant amount of credit deterioration since origination (PCD financial assets). The amendments are effective for public companies for fiscal years beginning after December 15, 2019, including interim periods within those fiscal years. Companies may early adopt this guidance as of the fiscal years beginning after December 15, 2018, including interim periods within those fiscal years. The amendments will be adopted following a modified-retrospective approach resulting in a cumulative effect adjustment in retained earnings as of the beginning of the year of adoption. Two exceptions to this adoption method are for PCD financial assets and debt securities for which other-than-temporary impairment (OTTI) will have been recognized before the effective date. Loans purchased with credit deterioration accounted for under current U.S. GAAP as "purchased credit impaired" (PCI) financial assets will be classified as PCD financial assets at transition and PCD guidance will be applied prospectively. Debt securities that have experienced OTTI before the effective date will follow a prospective adoption method which allows an entity to maintain the same amortized cost basis before and after the effective date.	The Company has identified certain financial instruments in scope of this guidance to include certain fixed maturity securities, loan and loan receivables and reinsurance recoverables (See Notes 3 and 7 for current balances of instruments in scope). The Company is continuing its progress towards updating its credit loss projection models and accounting systems in order to comply with the required changes in measurement of credit losses. The Company currently expects loans and loan receivables and held-to-maturity fixed maturity securities to be the asset classes most significantly impacted upon adoption of the guidance. The Company continues to evaluate the impact of adoption of this guidance on its financial position, results of operations, and disclosures.

Standard	Description	Effect on Financial Statements or Other Significant Matters
ASU 2016-02 Leases	In February 2016, the FASB issued updated guidance for accounting for leases. Per the amendments, lessees will be required to recognize all leases on the balance sheet with the exception of short-term leases. A lease liability will be recorded for the obligation of a lessee to make lease payments arising from a lease. A right-of-use asset will be recorded which represents the lessee’s right to control the use of a specified asset for a lease term. Under the new guidance, lessor accounting is largely unchanged. The amendments are effective for public companies for fiscal years beginning after December 15, 2018, including interim periods within those fiscal years. Early adoption is permitted, including adoption in an interim period.	The Company has identified certain operating leases in scope of this guidance to include office space and equipment leases (See Note 15 of the Notes to the Consolidated Financial Statements in the 2017 Annual Report for current balances of leases in scope). The leases within scope of this guidance will increase the Company's right-of-use assets and lease liabilities recorded on its statement of financial position, however the Company estimates leases within scope of the guidance to represent less than 1% of its total assets as of June 30, 2018. The Company estimates that the adoption of this guidance will not have a significant impact on its financial position, results of operations, or disclosures.