SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies)

3 Months Ended

Mar. 31, 2019

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 and, effective April 1, 2018, through Aflac Life Insurance Japan Ltd. (ALIJ) in Japan. Prior to April 1, 2018, the Company's insurance business was marketed in Japan as a branch of Aflac. The Company’s operations consist of two reportable business segments: Aflac U.S., which includes Aflac, and Aflac Japan, which includes ALIJ. 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 68% and 71% of the Company's total revenues in the three-month periods ended March 31, 2019 and 2018, respectively. The percentage of the Company's total assets attributable to Aflac Japan was 84% at March 31, 2019 and December 31, 2018, respectively.

Basis of Presentation

The Company prepares its financial statements in accordance with U.S. generally accepted accounting principles (U.S. 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 March 31, 2019, and December 31, 2018, the consolidated statements of earnings and comprehensive income (loss), shareholders' equity and cash flows for the three-month periods ended March 31, 2019 and 2018. 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, 2018 (2018 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.

Recently Adopted Accounting Pronouncements

Recently Adopted Accounting Pronouncements

Standard	Description	Date of Adoption	Effect on Financial Statements or Other Significant Matters
Accounting Standard Update (ASU) 2018-15 Intangibles - Goodwill and Other - Internal-Use Software, Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract	In August 2018, the FASB issued amendments to align the requirements for capitalizing implementation costs incurred in a hosting arrangement that is a service contract with the requirements for capitalizing implementation costs incurred to develop or obtain internal-use software.	Early adopted as of January 1, 2019	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 2016-02 Leases as clarified and amended by: ASU 2018-01, Leases: Land Easement Practical Expedient for Transition to Topic 842, ASU 2018-10, Codification Improvements to Topic 842, Leases, ASU 2018-11, Leases, Targeted Improvements, and ASU 2018-20, Leases: Narrow-Scope Improvements for Lessors	In February 2016, the FASB issued updated guidance for accounting for leases (“Leases Update”). Per the Leases Update, lessees are 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. Leases will be classified as finance or operating, with classification affecting the pattern and classification of expense recognition in the income statement. The Leases Update provided a number of optional practical expedients. The Company elected the "package of practical expedients," which permits the Company not to reassess under the new standard its prior conclusions about lease identification, lease classification and initial direct costs. Under the Leases Update, lessor accounting is largely unchanged. In January 2018, an amendment was issued to the Leases Update which provided an entity with the option to elect a transition practical expedient to not evaluate land easements that exist or expired before the entity's adoption of the Leases Update and that were not previously accounted for as leases. In July 2018, the FASB issued two amendments to the Leases Update which clarified, corrected errors in, or made minor improvements to the Leases Update and provided entities with an optional transition method to adopt the Leases Update by recording a cumulative-effect adjustment to beginning retained earnings. Additionally, the amendments provided lessors with a practical expedient to not separate nonlease components from associated lease components and instead account for those components as a single component under certain conditions. In December 2018, an amendment to the Leases Update was issued to clarify: 1) lessor accounting for all sales (and other similar) taxes; 2) the handling of certain lessor costs when the amount of those costs is not readily determinable; and 3) lessor allocation of certain variable payments to the lease and non-lease components.	January 1, 2019	The Company has operating and finance leases for office space and equipment. The Company elected the short-term lease exemption for all classes of leases which allows the Company to not recognize right-of-use assets and lease liabilities on the consolidated balance sheet and allows the Company to recognize the lease expense for short-term leases on a straight-line basis over the lease term. The Company elected the practical expedient to not separate lease and non-lease components and applied it to all classes of leases where the non-lease components are not significant. Some of the Company's leases include options to extend or terminate the lease and the lease terms may include such options when it is reasonably certain that the Company will exercise that option. Certain leases also include options to purchase the leased property. The leases within scope of the Leases Update increased the Company's right-of-use assets and lease liabilities recorded in its consolidated balance sheet by $134 million. As of January 1, 2019, the Company did not have land easements, but has elected the practical expedient as a safe harbor. The Company elected the optional transition method and as a safe harbor, the practical expedient provided to lessors. The Company has made an accounting policy election to exclude amounts collected from customers for all sales (and other similar) taxes from the transaction price. The adoption of the Leases Update and related amendments 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 2018-17 Consolidation: Targeted Improvements to Related Party Guidance for Variable Interest Entities	In October 2018, the FASB issued targeted improvements which provide that indirect interests held through related parties under common control should be considered on a proportional basis for determining whether fees paid to decision makers and service providers are variable interests. The amendments are effective for public business entities for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2019. 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 2018-14 Compensation - Retirement Benefits - Defined Benefit Plans - General, Disclosure Framework - Changes to the Disclosure Requirements for Defined Benefit Plans	In August 2018, the FASB issued amendments to modify the disclosure requirements for employers that sponsor defined benefit pension or other postretirement plans. Accordingly, six disclosures requirements were removed, two added and two clarified. The amendments are effective for public business entities for fiscal years beginning after December 15, 2020. 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 2018-13 Fair Value Measurement, Disclosure Framework - Changes to the Disclosure Requirements for Fair Value Measurement	In August 2018, the FASB issued amendments to the disclosure requirements on fair value measurements. The amendments remove, modify, and add certain disclosures. The amendments are effective for all entities for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2019. Early adoption is permitted. Further, an entity is permitted to early adopt any removed or modified disclosures upon issuance of this update and delay adoption of the additional disclosures until their effective date.	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 2018-12 Financial Services - Insurance, Targeted Improvements to the Accounting for Long-Duration Contracts	In August 2018, the FASB issued amendments that will significantly change how insurers account for long-duration contracts. The amendments will change existing recognition, measurement, presentation, and disclosure requirements. Issues addressed in the new guidance include: 1) a requirement to review and, if there is a change, update assumptions for the liability for future policy benefits at least annually, and to update the discount rate assumption quarterly, 2) accounting for market risk benefits at fair value, 3) simplified amortization for deferred acquisition costs, and 4) enhanced financial statement presentation and disclosures. The amendments are effective for public business entities for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2020. Early application of the amendments is permitted.	The Company is thoroughly evaluating the impact of adoption and expects that the adoption will have a significant impact on the Company’s financial position, results of operations, and disclosures. The Company anticipates that the requirement to update assumptions for liability for future policy benefits will have a significant impact on its results of operations, systems, processes and controls while the requirement to update the discount rate will have a significant impact on its equity. The Company has no products with market risk benefits. The Company does not expect to early adopt the updated standard.
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.

Standard	Description	Effect on Financial Statements or Other Significant Matters
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, loans 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.