SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies)	3 Months Ended
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies)	Mar. 31, 2017
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), which operates in the United States (Aflac U.S.) and as a branch in Japan (Aflac Japan). 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. Our insurance operations in the United States and our branch in Japan service the two markets for our insurance business. Aflac Japan's revenues, including realized gains and losses on its investment portfolio, accounted for 69% and 74% of the Company's total revenues in the three-month periods ended March 31, 2017, and 2016, respectively. The percentage of the Company's total assets attributable to Aflac Japan was 84% at March 31, 2017, compared with 83% at December 31, 2016. Basis of Presentation We prepare our 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 us to make estimates when recording transactions resulting from business operations based on currently available information. The most significant items on our 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, 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, we believe 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 March 31, 2017 and December 31, 2016, the consolidated statements of earnings and comprehensive income (loss), shareholders' equity and cash flows for the three-month periods ended March 31, 2017 and 2016. 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 our annual report on Form 10-K for the year ended December 31, 2016 (2016 Annual Report).
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. Prior year foreign currency transaction gains and losses have been reclassified from Other income (loss) to Realized investment gains (losses) - Derivative and other gains (losses) to conform to current-year reporting classifications. These reclassifications had no impact on net earnings or total shareholders' equity. This change in classification was made to reflect that the major source of our foreign currency transaction gains and losses is directly or indirectly a result of our investment activity.
Recently Adopted Accounting Pronouncements	Recently Adopted Accounting Pronouncements Consolidation - Interests Held through Related Parties That Are under Common Control: In October 2016, the FASB issued amendments which clarify the consolidation guidance on how a reporting entity that is the single decision maker of a variable interest entity (VIE) should treat indirect interests in the entity held through related parties that are under common control with the reporting entity when determining whether it is the primary beneficiary of that VIE. We adopted this guidance as of January 1, 2017. The adoption of this guidance did not have a significant impact on our financial position, results of operations, or disclosures. Compensation - Stock Compensation - Improvements to Employee Share-Based Payment Accounting: In March 2016, the FASB issued amendments which simplify several aspects for share-based payment award transactions, including income tax consequences, classification of awards as either liability or equities, and classification on the statement of cash flows. We adopted this guidance as of January 1, 2017. The amendment requires prospective recognition of excess tax benefits and deficiencies in the income statement, rather than in paid-in capital. As a result of applying this requirement, we believe that recognition of excess tax benefits will increase volatility in our statement of operations but the adoption of this guidance did not have a significant impact on our statement of financial position, operations, or disclosures. The amendment also requires all excess tax benefits and tax deficiencies (including tax benefits of dividends on share-based payment awards) to be recognized as income tax expense or benefit in the income statement. The guidance requires modified retrospective transition for settlements on all outstanding awards (both historical and future) that did not give rise to an excess benefit to be recorded through retained earnings on a cumulative-effect basis. The adoption of these amendments in the guidance did not have a significant impact on our financial position, results of operations, or disclosures. Additionally, the amendment requires that the minimum statutory tax withholding for all outstanding liability awards be reclassified at the date of adoption to equity (assuming equity classification results from the guidance change), and as a cumulative-effect adjustment to equity be recorded on a modified retrospective basis. The adoption of these amendments in the guidance did not have a significant impact on our financial position, results of operations, or disclosures. The guidance requires certain reclassifications of balances on the statement of cash flows to or from operating and financing activities. The reclassification guidance did not have a significant impact on our statement of cash flows. The amendment allows an entity to elect whether to use estimates of forfeitures, or to account for forfeitures as they occur, using modified retrospective application. We have made an entity-wide accounting policy election to estimate the number of awards that are expected to vest (consistent with our prior policy). The election and adoption of this guidance did not have a significant impact on our financial position, results of operations, or disclosures. Investments - Equity Method and Joint Ventures - Simplifying the Transition to the Equity Method of Accounting: In March 2016, the FASB issued amendments which eliminate the requirement that when an investment qualifies for use of the equity method as a result of an increase in the level of ownership interest or degree of influence, an investor must adjust the investment, results of operations, and retained earnings retroactively on a step-by-step basis as if the equity method had been in effect during all previous periods that the investment had been held. Per the amendments, upon qualifying for the equity method of accounting, no retroactive adjustment of the investment is required. The amendments also require that an entity that has an available-for-sale equity security that becomes qualified for the equity method of accounting recognize through earnings the unrealized holding gain or loss in accumulated other comprehensive income at the date the investment becomes qualified for use of the equity method. We adopted this guidance as of January 1, 2017. The adoption of this guidance did not have a significant impact on our financial position, results of operations, or disclosures. Derivatives and Hedging - Contingent Put and Call Options in Debt Instruments: In March 2016, the FASB issued amendments which clarify what steps are required when assessing whether the economic characteristics and risks of call (put) options are clearly and closely related to the economic characteristics and risks of their debt hosts, which is one of the criteria for bifurcating an embedded derivative. Consequently, when a call (put) option is contingently exercisable, an entity does not have to assess whether the event that triggers the ability to exercise a call (put) option is related to interest rates or credit risks. We adopted this guidance as of January 1, 2017. The adoption of this guidance did not have a significant impact on our financial position, results of operations, or disclosures. Derivatives and Hedging - Effect of Derivative Contract Novations on Existing Hedge Accounting Relationships: In March 2016, the FASB issued amendments which clarify that a change in the counterparty to a derivative instrument that has been designated as the hedging instrument does not, in and of itself, require dedesignation of that hedging relationship provided that all other hedge accounting criteria remain intact. We adopted this guidance as of January 1, 2017. The adoption of this guidance did not have a significant impact on our financial position, results of operations, or disclosures. Financial Services - Insurance - Disclosures about Short-Duration Contracts: In May 2015, the FASB issued updated guidance requiring enhanced disclosures by all insurance entities that issue short-duration contracts. The amendments require insurance entities to disclose for annual reporting periods information about the liability for unpaid claims and claim adjustment expenses. The amendments also require insurance entities to disclose information about significant changes in methodologies and assumptions used to calculate the liability for unpaid claims and claim adjustment expenses. In addition, the amendments require insurance entities to disclose for annual and interim reporting periods a roll-forward of the liability for unpaid claims and claim adjustment expenses. For health insurance claims, the amendments require the disclosure of the total of incurred-but-not-reported liabilities and expected development on reported claims included in the liability for unpaid claims and claim adjustment expenses. We adopted this guidance as of December 31, 2016, and have no insurance contracts classified as short-duration. The adoption of this guidance did not have a significant impact on our disclosures. Presentation of Financial Statements - Going Concern - Disclosure of Uncertainties about an Entity’s Ability to Continue as a Going Concern: In August 2014, the FASB issued this amendment that provides U.S. GAAP guidance on management’s responsibility in evaluating whether there is substantial doubt about a company’s ability to continue as a going concern and about related footnote disclosures. For each reporting period, management will be required to evaluate whether there are conditions or events that raise substantial doubt about a company’s ability to continue as a going concern within one year from the date the financial statements are issued. The new guidance requires a formal assessment of going concern by management based on criteria prescribed in the new guidance. We adopted this guidance as of December 31, 2016. The adoption of this guidance did not have a significant impact on our financial position, results of operations, or disclosures, and no substantial doubt currently exists about the Company’s ability to continue as a going concern.
Description of Accounting Pronouncements Pending Adoption	Accounting Pronouncements Pending Adoption 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 our financial position, results of operations, or disclosures. Compensation-Retirement Benefit: 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. The amendments are effective for public business entities for fiscal years beginning after December 15, 2017, 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 our financial position, results of operations, disclosures, or statements of cash flows. 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 clarifying that the accounting guidance for derecognition of nonfinancial assets does not apply to the derecognition of businesses, nonprofit activities or financial assets that meet the definition of "in substance nonfinancial assets." The new guidance defines an "in substance nonfinancial asset" to be an asset or group of assets for which substantially all of the fair value consists of nonfinancial assets and the group or subsidiary is not a business. The amendments are effective for public business entities for fiscal years beginning after December 15, 2017, and interim periods within those fiscal years. Earlier adoption is permitted for fiscal years beginning after December 15, 2016, including interim periods therein. An entity is required to apply the amendments at the same time that it applies the FASB amendments for Revenue from Contracts with Customers. We are evaluating the impact of adoption of this guidance on our financial position, results of operations, disclosures, and statements of cash flows. 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 U.S. SEC filers for annual or any interim goodwill impairment tests in fiscal years beginning after Dec. 15, 2019. Early adoption is permitted for any goodwill impairment tests performed on testing dates after January 1, 2017. We do not expect the adoption of this guidance to have a significant impact on our financial position, results of operations, or disclosures. 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 determine when a set of assets and activities is not a business. The amendments are effective for public business entities beginning after December 15, 2017, including interim periods within those periods. We do not expect the adoption of this guidance to have a significant impact on our financial position, results of operations, or disclosures. 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. The amendments are effective for public business entities for fiscal years beginning after December 15, 2017, and interim periods within those fiscal years. Early adoption is permitted. We do not expect the adoption of this guidance to have a significant impact on our financial position, results of operations, disclosures or statement of cash flows. 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. The amendments are effective for public business entities for annual reporting periods beginning after December 15, 2017, including interim reporting periods within those annual reporting periods. Early adoption is permitted. We are evaluating the impact of adoption of this guidance on our financial position, results of operations and disclosures. 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. The amendments are effective for public companies for fiscal years beginning after December 15, 2017, and interim periods within those fiscal years. Early adoption is permitted for any interim or annual period. The adoption of this guidance is not expected to have a significant impact on our financial position, results of operations, disclosures, or statements of cash flows. 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 writedown. 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. 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. We have identified certain financial instruments in scope of this guidance to include certain fixed maturity securities, loans and loan receivables and reinsurance recoverables (See Notes 3 and 7 for current balances of instruments in scope). We are continuing to evaluate the impact of adoption of this guidance on our financial position, results of operations and disclosures. 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 use, or 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. We have 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 2016 Annual Report for current balances of leases in scope). The leases within scope of this guidance will increase our right-of-use assets recorded on our financial position, however we estimate leases within scope of the guidance to represent less than 1% of our total assets as of March 31, 2017. We estimate that the adoption of this guidance will not have a significant impact on our financial position, results of operations and disclosures. 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 require that equity investments be measured at fair value with changes recognized in net income; that changes in instrument-specific credit risk for financial liabilities that are measured under the fair value option be recognized in other comprehensive income; and that entities would make the assessment of the ability to realize a deferred tax asset (DTA) related to an available-for-sale (AFS) debt security in combination with the entity's other DTAs. The amendments are effective for public companies for fiscal years beginning after December 15, 2017, including interim periods within those fiscal years. Early adoption is not permitted, with the exception of the own credit provision if an entity has elected to measure a liability at fair value. We have identified certain financial instruments in scope of this guidance to include certain fixed maturity securities, perpetual securities and equity securities (See Note 3 for current balances of instruments in scope). We estimate that the impact of this guidance will increase volatility in our statement of operations and we are continuing to evaluate the impact of this guidance on our statement of financial position, operations and disclosures. 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. In August 2015, the FASB deferred the effective date for this standard to annual reporting periods beginning after December 15, 2017, including interim periods within that reporting period. Earlier application is permitted only as of annual reporting periods beginning after December 15, 2016, including interim reporting periods. We have identified revenue in scope of this guidance to include certain revenues associated with affiliated entities in support of our operations. We estimate the revenue within scope of the guidance to represent less than 1% of our total revenues as of March 31, 2017. We estimate that the adoption of this guidance will not have a significant impact on our financial position, results of operations and disclosures.