Aflac (AFL) 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	Apr. 25, 2018
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Mar. 31, 2018
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	Q1
Trading Symbol	AFL
Entity Registrant Name	AFLAC INC
Entity Central Index Key	4,977
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		774,167,054

Consolidated Statements of Earn

Consolidated Statements of Earnings - USD ($) shares in Thousands, $ in Millions		3 Months Ended
		Mar. 31, 2018	Mar. 31, 2017
Revenues:
Net premiums, principally supplemental health insurance		$ 4,745	$ 4,638
Net investment income		837	794
Realized investment gains (losses):
Other-than-temporary impairment losses realized		(7)	(10)
Other gains (losses)	[1]	(127)	(130)
Total realized investment gains (losses)		(134)	(140)
Other income (loss)		16	17
Total revenues		5,464	5,309
Benefits and expenses:
Benefits and claims, net		3,042	3,052
Acquisition and operating expenses:
Amortization of deferred policy acquisition costs		314	294
Insurance commissions		337	328
Insurance and other expenses		733	675
Interest expense		56	62
Total acquisition and operating expenses		1,440	1,359
Total benefits and expenses		4,482	4,411
Earnings before income taxes		982	898
Income taxes		265	306
Net earnings		$ 717	$ 592
Net earnings per share:
Basic (in dollars per share)		$ 0.92	$ 0.74
Diluted (in dollars per share)		$ 0.91	$ 0.73
Weighted-average outstanding common shares used in computing earnings per share (In thousands):
Basic (in shares)		778,550	802,259
Diluted (in shares)		783,852	808,138
Cash dividends per share		$ 0.26	$ 0.22
[1]	See Note 1 of the Notes to the Consolidated Financial Statements for the adoption of accounting guidance on January 1, 2018 related to financial instruments.

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2018	Mar. 31, 2017
Statement of Comprehensive Income [Abstract]
Net earnings		$ 717	$ 592
Other comprehensive income (loss) before income taxes:
Unrealized foreign currency translation gains (losses) during period		824	375
Unrealized gains (losses) on fixed maturity securities:
Unrealized holding gains (losses) on fixed maturity securities during period	[1]	(1,931)	(526)
Reclassification adjustment for realized (gains) losses on fixed maturity securities included in net earnings	[1]	(2)	16
Unrealized gains (losses) on derivatives during period		6	2
Pension liability adjustment during period		(3)	(2)
Total other comprehensive income (loss) before income taxes		(1,106)	(135)
Income tax expense (benefit) related to items of other comprehensive income (loss)		(763)	(137)
Other comprehensive income (loss), net of income taxes	[2]	(343)	2
Total comprehensive income (loss)		$ 374	$ 594
[1]	See Note 1 of the Notes to the Consolidated Financial Statements for the adoption of accounting guidance on January 1, 2018 related to financial instruments.
[2]	All amounts in the table above are net of tax.

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Millions		Mar. 31, 2018	Dec. 31, 2017
Securities available for sale, at fair value:
Fixed maturities	[1]	$ 89,033
Securities held to maturity, at amortized cost:
Fixed maturities		33,377	$ 31,430
Equity securities, at fair value:
Equity securities	[2],[3]	1,108
Other investments	[4]	5,073	3,402
Cash and cash equivalents		4,080	3,491
Total investments and cash		132,671	123,659
Receivables		906	827
Accrued investment income		745	769
Deferred policy acquisition costs		9,933	9,505
Property and equipment, at cost less accumulated depreciation		448	434
Other	[5]	2,653	2,023
Total assets		147,356	137,217
Policy Liabilities:
Future policy benefits		87,268	81,857
Unpaid policy claims		4,630	4,392
Unearned premiums		6,084	5,959
Other policyholders’ funds		7,417	6,939
Total policy liabilities		105,399	99,147
Income taxes		4,407	4,745
Payables for return of cash collateral on loaned securities		5,368	606
Notes payable		5,372	5,289
Other	[6]	2,523	2,832
Total liabilities		123,069	112,619
Shareholders’ equity:
Common stock of $.10 par value. In thousands: authorized 3,800,000 shares in 2018 and 2017; issued 1,346,776 shares in 2018 and 1,345,762 shares in 2017		135	135
Additional paid-in capital		2,089	2,052
Retained earnings		30,183	29,895
Accumulated other comprehensive income (loss):
Unrealized foreign currency translation gains (losses)		(1,303)	(1,750)
Unrealized gain (losses) on fixed maturity securities	[7],[8]	5,206	5,964
Unrealized gains (losses) on derivatives		(21)	(23)
Pension liability adjustment		(197)	(163)
Treasury stock, at average cost		(11,805)	(11,512)
Total shareholders’ equity		24,287	24,598
Total liabilities and shareholders’ equity		147,356	137,217
Consolidated Entity Excluding Variable Interest Entities (VIE)
Securities available for sale, at fair value:
Fixed maturities	[9]	83,602	78,804
Securities held to maturity, at amortized cost:
Fixed maturities		33,377	31,430
Equity securities, at fair value:
Equity securities	[9]	348
Available-for-sale securities, equity securities	[9]		270
Variable Interest Entity, Consolidated
Securities available for sale, at fair value:
Fixed maturities	[9],[10]	5,431	5,509
Equity securities, at fair value:
Equity securities		760
Available-for-sale securities, equity securities			753
Other investments	[11]	3,994	2,341
Policy Liabilities:
Total liabilities		$ 86	$ 128
[1]	Includes perpetual securities, categorized in accordance with their respective economic maturities (the expected maturity date created by the combination of features in the financial instrument)
[2]	Includes perpetual securities
[3]	Includes perpetual securities ($71 at fair value)
[4]	Includes $3,994 in 2018 and $2,341 in 2017 of loan receivables and limited partnerships from consolidated variable interest entities
[5]	Includes $241 in 2018 and $151 in 2017 of derivatives from consolidated variable interest entities
[6]	Includes $86 in 2018 and $128 in 2017 of derivatives from consolidated variable interest entities
[7]	See Note 1 for discussion of the accounting treatment of tax on amounts recorded in accumulated other comprehensive income pursuant to the Tax Act and for the adoption of accounting guidance on January 1, 2018 related to financial instruments.
[8]	See Note 1 of the Notes to the Consolidated Financial Statements for the adoption of accounting guidance on January 1, 2018 related to financial instruments.
[9]	Includes perpetual securities, see Notes 1 and 3 of the Notes to the Consolidated Financial Statements
[10]	Includes perpetual securities
[11]	Consists of TREs, CMLs, MMLs, and alternative investments in limited partnerships

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions		Mar. 31, 2018	Dec. 31, 2017
Securities available for sale, fixed maturities, amortized cost	[1]	$ 81,607
Securities held to maturity, fixed maturities, fair value		$ 40,468	$ 38,072
Common stock, par value (in dollars per share)		$ 0.1	$ 0.1
Common stock, shares authorized (in shares)		3,800,000,000	3,800,000,000
Common stock, shares issued (in shares)		1,346,776,000	1,345,762,000
Asset derivatives		$ 797	$ 331
Liability derivatives		353	474
Variable Interest Entity, Consolidated
Securities available for sale, fixed maturities, amortized cost	[2],[3]	4,695	4,538
Asset derivatives	[4]	241	151
Liability derivatives	[4]	86	128
Consolidated Entity Excluding Variable Interest Entities (VIE)
Securities available for sale, fixed maturities, amortized cost	[3]	76,912	70,594
Securities held to maturity, fixed maturities, fair value		40,468	38,072
Loan Receivables and Limited Partnerships | Variable Interest Entity, Consolidated
Other investments held in unit trust, net of reserves, amortized cost		$ 3,994	$ 2,341
[1]	Includes perpetual securities, categorized in accordance with their respective economic maturities (the expected maturity date created by the combination of features in the financial instrument)
[2]	Includes perpetual securities
[3]	Includes perpetual securities, see Notes 1 and 3 of the Notes to the Consolidated Financial Statements
[4]	Consists entirely of derivatives

Consolidated Statements of Shar

Consolidated Statements of Shareholders' Equity - USD ($) $ in Millions		Total	Common stock:	Additional paid-in capital:	Retained earnings:	Accumulated other comprehensive income (loss):	Treasury stock:
Balance, beginning of period at Dec. 31, 2016			$ 135	$ 1,908	$ 25,981	$ 2,630	$ (10,172)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of stock options				10
Share-based compensation				12
Treasury stock reissued				10			15
Net earnings		$ 592			592
Dividends to shareholders					(173)
Unrealized foreign currency translation gains (losses) during period, net of income taxes						333
Unrealized gains (losses) on fixed maturity securities during period, net of income taxes and reclassification adjustments	[1]					(331)
Unrealized gains (losses) on derivatives during period, net of income taxes						2
Pension liability adjustment during period, net of income taxes						(2)
Purchases of treasury stock							(610)
Balance, end of period at Mar. 31, 2017		20,340	135	1,940	26,400	2,632	(10,767)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect of change in accounting principle, net of income taxes | Accounting Standards Update 2016-01	[1]				0	0
Cumulative effect of change in accounting principle, net of income taxes | Accounting Standards Update 2018-02	[1]				0	0
Balance, beginning of period at Dec. 31, 2017		24,598	135	2,052	29,895	4,028	(11,512)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of stock options				14
Share-based compensation				10
Treasury stock reissued				13			16
Net earnings		717			717
Dividends to shareholders					(203)
Unrealized foreign currency translation gains (losses) during period, net of income taxes						447
Unrealized gains (losses) on fixed maturity securities during period, net of income taxes and reclassification adjustments	[1]					(984)
Unrealized gains (losses) on derivatives during period, net of income taxes						2
Pension liability adjustment during period, net of income taxes						(34)
Purchases of treasury stock							(309)
Balance, end of period at Mar. 31, 2018		$ 24,287	$ 135	$ 2,089	30,183	3,685	$ (11,805)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect of change in accounting principle, net of income taxes | Accounting Standards Update 2016-01	[1]				148	(148)
Cumulative effect of change in accounting principle, net of income taxes | Accounting Standards Update 2018-02	[1]				$ (374)	$ 374
[1]	See Note 1 of the Notes to the Consolidated Financial Statements for the adoption of accounting guidance on January 1, 2018.

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Cash flows from operating activities:
Net earnings	$ 717	$ 592
Adjustments to reconcile net earnings to net cash provided by operating activities:
Change in receivables and advance premiums	14	106
Capitalization of deferred policy acquisition costs	(349)	(335)
Amortization of deferred policy acquisition costs	314	294
Increase in policy liabilities	572	666
Change in income tax liabilities	(131)	271
Realized investment (gains) losses	134	140
Other, net	(33)	23
Net cash provided (used) by operating activities	1,238	1,757
Securities available for sale:
Fixed maturity securities sold	433	1,385
Fixed maturity securities matured or called	510	204
Equity securities sold	157	155
Securities held to maturity:
Fixed maturity securities matured or called	50	228
Other investments - loan receivables proceeds	146	34
Costs of investments acquired:
Available for sale fixed maturity securities acquired	(3,975)	(3,726)
Equity securities acquired	(166)	(157)
Other investments, loan receivables acquired	(1,772)	(123)
Other investments, excluding loan receivables. net	(125)	(114)
Settlement of derivatives, net	(1)	(44)
Cash received (pledged or returned) as collateral, net	4,578	654
Other, net	(34)	(23)
Net cash provided (used) by investing activities	(199)	(1,527)
Cash flows from financing activities:
Purchases of treasury stock	(296)	(610)
Proceeds from borrowings	2	524
Principal payments under debt obligations	0	(654)
Dividends paid to shareholders	(195)	(166)
Change in investment-type contracts, net	7	18
Treasury stock reissued	14	11
Other, net	(5)	1
Net cash provided (used) by financing activities	(473)	(876)
Effect of exchange rate changes on cash and cash equivalents	23	(8)
Net change in cash and cash equivalents	589	(654)
Cash and cash equivalents, beginning of period	3,491	4,859
Cash and cash equivalents, end of period	4,080	4,205
Supplemental disclosures of cash flow information:
Income taxes paid	396	58
Interest paid	36	47
Noncash interest	21	15
Impairment losses included in realized investment losses	7	10
Noncash financing activities:
Capital lease obligations	1	2
Associate stock bonus
Treasury stock issued for:
Treasury stock issued	5	6
Shareholder dividend reinvestment
Treasury stock issued for:
Treasury stock issued	8	7
Share-based compensation grants
Treasury stock issued for:
Treasury stock issued	$ 2	$ 1

SUMMARY OF SIGNIFICANT ACCOUNTI

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	3 Months Ended
	Mar. 31, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES 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 as a branch in Japan (Aflac Japan). The conversion of Aflac Japan from a branch to a legal subsidiary was completed on April 1, 2018 (see Note 14), after which date 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 through Aflac Life Insurance Japan Ltd. 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. 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 71% and 69% of the Company's total revenues in the three -month periods ended March 31, 2018 and 2017 , respectively. The percentage of the Company's total assets attributable to Aflac Japan was 85% at March 31, 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 March 31, 2018 , and December 31, 2017 , the consolidated statements of earnings and comprehensive income (loss), shareholders' equity and cash flows for the three -month periods ended March 31, 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 : 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. New Accounting Pronouncements Recently Adopted Accounting Pronouncements 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. The Company elected to early adopt this technical correction and improvement guidance 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. 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. The Company elected to early adopt this guidance 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. 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. The Company adopted this guidance 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. 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 Company adopted this guidance 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, statements of cash flows, or disclosures. 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. The Company adopted this guidance 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, statements of cash flows, 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 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. The Company adopted this guidance 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. 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 Company adopted this guidance 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, statements of cash flows, or disclosures. 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 Company adopted this guidance 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. Statement of Cash Flows - Classification of Certain Cash Receipts and Cash Payment s : In August 2016, the FASB issued amendments that provide guidance on eight specific statement of cash flows classification issues. The Company adopted this guidance 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, statements of cash flows, or 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 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. The Company adopted this guidance as of 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. 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. The Company adopted this guidance 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. Accounting Pronouncements Pending Adoption Leases - Land Easement Practical Expedient for Transition to Topic 842: In January 2018, 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. Derivatives and Hedging - Targeted Improvements to Accounting for Hedging Activities: In August 2017, 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. 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. 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 Company does not expect the adoption of this guidance to have a significant impact on its financial position, results of operations, or disclosures. 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. 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. 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 March 31, 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. Recent accounting guidance not discussed above is not applicable, did not have, or is not expected to have a material impact to the Company's business. For additional information on new accounting pronouncements and recent accounting guidance and their impact, if any, on the Company's financial position or results of operations, see Note 1 of the Notes to the Consolidated Financial Statements in the 2017 Annual Report.

BUSINESS SEGMENT INFORMATION

BUSINESS SEGMENT INFORMATION	3 Months Ended
	Mar. 31, 2018
Segment Reporting [Abstract]
BUSINESS SEGMENT INFORMATION	BUSINESS SEGMENT INFORMATION The Company consists of two reportable insurance business segments: Aflac Japan and Aflac U.S., both of which sell supplemental health and life insurance. Operating business segments that are not individually reportable and business activities, including reinsurance retrocession activities, not included in Aflac Japan or Aflac U.S. are included in the "Corporate and other" category. The Company does not allocate corporate overhead expenses to business segments. Consistent with U.S. GAAP accounting guidance for segment reporting, the Company evaluates and manages its business segments using a financial performance measure called pretax adjusted earnings. Adjusted earnings are adjusted revenues less benefits and adjusted expenses. The adjustments to both revenues and expenses account for certain items that cannot be predicted or that are outside management’s control. Adjusted revenues are U.S. GAAP total revenues excluding realized investment gains and losses, except for amortized hedge costs related to foreign currency denominated investments. Adjusted expenses are U.S. GAAP total acquisition and operating expenses including the impact of interest cash flows from derivatives associated with notes payable but excluding any nonrecurring or other items not associated with the normal course of the Company’s insurance operations and that do not reflect Aflac’s underlying business performance. The Company excludes income taxes related to operations to arrive at pretax adjusted earnings. Information regarding operations by segment follows: Three Months Ended (In millions) 2018 2017 Revenues: Aflac Japan: Net earned premiums $ 3,263 $ 3,194 Net investment income, less amortized hedge costs (1) 588 557 Other income 12 10 Total Aflac Japan 3,863 3,761 Aflac U.S.: Net earned premiums 1,427 1,390 Net investment income 175 178 Other income 2 1 Total Aflac U.S. 1,604 1,569 Corporate and other (2) 79 67 Total adjusted revenues 5,546 5,397 Realized investment gains (losses) (1),(2) (82 ) (88 ) Total revenues $ 5,464 $ 5,309 (1) Amortized hedge costs related to hedging U.S. dollar-denominated investments held in Aflac Japan were $55 and $52 for the three -month periods ended March 31, 2018 , and 2017 , respectively, and have been reclassified from realized investment gains (losses) and reported as a deduction from net investment income when analyzing segment operations. (2) Amortized hedge costs in Aflac Japan were offset by derivatives entered into as part of corporate activities and resulted in a benefit of $2 for the three -month period ended March 31, 2018 which has been reclassified from realized investment gains (losses) and reported as an increase in net investment income when analyzing operations. Three Months Ended (In millions) 2018 2017 Pretax earnings: Aflac Japan (1) $ 818 $ 769 Aflac U.S. 337 310 Corporate and other (2) (46 ) (52 ) Pretax adjusted earnings 1,109 1,027 Realized investment gains (losses) (1),(2),(3) (98 ) (109 ) Other income (loss) (29 ) (20 ) Total earnings before income taxes $ 982 $ 898 Income taxes applicable to pretax adjusted earnings $ 289 $ 351 Effect of foreign currency translation on after-tax 21 5 (1) Amortized hedge costs related to hedging U.S. dollar-denominated investments held in Aflac Japan were $55 and $52 for the three -month periods ended March 31, 2018 , and 2017 , respectively, and have been reclassified from realized investment gains (losses) and reported as a deduction from pretax adjusted earnings when analyzing segment operations. (2) Amortized hedge costs in Aflac Japan were offset by derivatives entered into as part of corporate activities and resulted in a benefit of $2 for the three-month period ended March 31, 2018 which has been reclassified from realized investment gains (losses) and reported as an increase in pretax adjusted earnings when analyzing operations. (3) Excluding a gain of $17 and $21 for the three -month periods ended March 31, 2018 , and 2017 , respectively, related to the interest rate component of the change in fair value of foreign currency swaps on notes payable which is included in adjusted earnings when analyzing segment operations Assets were as follows: (In millions) March 31, December 31, Assets: Aflac Japan $ 125,174 $ 114,402 Aflac U.S. 19,706 19,893 Corporate and other 2,476 2,922 Total assets $ 147,356 $ 137,217

INVESTMENTS

INVESTMENTS	3 Months Ended
	Mar. 31, 2018
Investments [Abstract]
INVESTMENTS	INVESTMENTS Investment Holdings The amortized cost for the Company's investments in debt securities, the cost for equity securities and the fair values of these investments are shown in the following tables. March 31, 2018 (In millions) Cost or Gross Gross Fair Securities available for sale, carried at fair value Fixed maturity securities: (1) Yen-denominated: Japan government and agencies $ 32,961 $ 3,811 $ 192 $ 36,580 Municipalities 350 33 11 372 Mortgage- and asset-backed securities 254 30 0 284 Public utilities 1,739 325 4 2,060 Sovereign and supranational 1,348 212 27 1,533 Banks/financial institutions 5,157 799 76 5,880 Other corporate 4,345 754 8 5,091 Total yen-denominated 46,154 5,964 318 51,800 U.S. dollar-denominated: U.S. government and agencies 148 9 1 156 Municipalities 866 135 0 1,001 Mortgage- and asset-backed securities 165 7 1 171 Public utilities 5,223 631 107 5,747 Sovereign and supranational 274 59 0 333 Banks/financial institutions 2,841 457 34 3,264 Other corporate 25,936 1,736 1,111 26,561 Total U.S. dollar-denominated 35,453 3,034 1,254 37,233 Total securities available for sale $ 81,607 (1) $ 8,998 $ 1,572 $ 89,033 (1) (1) Includes perpetual securities ( $1,506 at amortized cost and $1,774 at fair value) March 31, 2018 (In millions) Cost or Gross Gross Fair Securities held to maturity, carried at amortized cost: Fixed maturity securities: Yen-denominated: Japan government and agencies $ 22,686 $ 5,631 $ 0 $ 28,317 Municipalities 379 114 0 493 Mortgage- and asset-backed securities 26 2 0 28 Public utilities 3,508 383 0 3,891 Sovereign and supranational 1,620 299 0 1,919 Banks/financial institutions 2,300 190 13 2,477 Other corporate 2,858 485 0 3,343 Total yen-denominated 33,377 7,104 13 40,468 Total securities held to maturity $ 33,377 $ 7,104 $ 13 $ 40,468 March 31, 2018 (In millions) Fair Equity securities, carried at fair value through net earnings: Equity securities: (1) Yen-denominated $ 711 U.S. dollar-denominated 397 Total equity securities $ 1,108 (1) (1) Includes perpetual securities ( $71 at fair value) December 31, 2017 (In millions) Cost or Gross Gross Fair Securities available for sale, carried at fair value: Fixed maturity securities: (1) Yen-denominated: Japan government and agencies $ 27,980 $ 3,363 $ 271 $ 31,072 Municipalities 314 28 12 330 Mortgage- and asset-backed securities 242 29 0 271 Public utilities 1,635 352 6 1,981 Sovereign and supranational 1,380 190 1 1,569 Banks/financial institutions 4,742 811 53 5,500 Other corporate 4,085 809 7 4,887 Total yen-denominated 40,378 5,582 350 45,610 U.S dollar-denominated: U.S. government and agencies 146 13 1 158 Municipalities 872 168 0 1,040 Mortgage- and asset-backed securities 161 12 0 173 Public utilities 5,116 884 27 5,973 Sovereign and supranational 267 73 0 340 Banks/financial institutions 2,808 633 8 3,433 Other corporate 25,384 2,620 418 27,586 Total U.S. dollar-denominated 34,754 4,403 454 38,703 Total securities available for sale $ 75,132 (1) $ 9,985 $ 804 $ 84,313 (1) (1) Includes perpetual securities ( $1,462 at amortized cost and $1,789 at fair value) December 31, 2017 (In millions) Cost or Gross Gross Fair Securities held to maturity, carried at amortized cost: Fixed maturity securities: Yen-denominated: Japan government and agencies $ 21,331 $ 5,160 $ 0 $ 26,491 Municipalities 357 105 0 462 Mortgage- and asset-backed securities 26 1 0 27 Public utilities 3,300 398 0 3,698 Sovereign and supranational 1,523 312 0 1,835 Banks/financial institutions 2,206 190 9 2,387 Other corporate 2,687 485 0 3,172 Total yen-denominated 31,430 6,651 9 38,072 Total securities held to maturity $ 31,430 $ 6,651 $ 9 $ 38,072 December 31, 2017 (In millions) Fair Equity securities, carried at fair value: Equity securities: Yen-denominated $ 695 U.S. dollar-denominated 328 Total equity securities $ 1,023 The methods of determining the fair values of the Company's investments in fixed maturity securities and equity securities are described in Note 5. During the first quarter of 2018 and 2017, respectively, the Company did not reclassify any investments from the held-to-maturity category to the available-for-sale category. Contractual and Economic Maturities The contractual and economic maturities of the Company's investments in fixed maturity securities at March 31, 2018 , were as follows: (In millions) Amortized Fair Available for sale: (1) Due in one year or less $ 485 $ 502 Due after one year through five years 9,685 9,551 Due after five years through 10 years 10,637 11,143 Due after 10 years 60,381 67,382 Mortgage- and asset-backed securities 419 455 Total fixed maturity securities available for sale $ 81,607 $ 89,033 Held to maturity: Due in one year or less $ 1,036 $ 1,049 Due after one year through five years 508 527 Due after five years through 10 years 1,597 1,754 Due after 10 years 30,210 37,110 Mortgage- and asset-backed securities 26 28 Total fixed maturity securities held to maturity $ 33,377 $ 40,468 (1) Includes perpetual securities, categorized in accordance with their respective economic maturities (the expected maturity date created by the combination of features in the financial instrument) Expected maturities may differ from contractual maturities because some issuers have the right to call or prepay obligations with or without call or prepayment penalties. Investment Concentrations The Company's process for investing in credit-related investments begins with an independent approach to underwriting each issuer's fundamental credit quality. The Company evaluates independently those factors that it believes could influence an issuer's ability to make payments under the contractual terms of the Company's instruments. This includes a thorough analysis of a variety of items including the issuer's country of domicile (including political, legal, and financial considerations); the industry in which the issuer competes (with an analysis of industry structure, end-market dynamics, and regulation); company specific issues (such as management, assets, earnings, cash generation, and capital needs); and contractual provisions of the instrument (such as financial covenants and position in the capital structure). The Company further evaluates the investment considering broad business and portfolio management objectives, including asset/liability needs, portfolio diversification, and expected income. Investment exposures that individually exceeded 10% of shareholders' equity were as follows: March 31, 2018 December 31, 2017 (In millions) Credit Amortized Fair Credit Amortized Fair Japan National Government (1) A $54,465 $63,576 A $48,399 $56,532 (1) Japan Government Bonds (JGBs) or JGB-backed securities Realized Investment Gains and Losses Information regarding pretax realized gains and losses from investments is as follows: Three Months Ended (In millions) 2018 2017 Realized investment gains (losses): Fixed maturity securities: (1) Available for sale: Gross gains from sales $ 9 $ 12 Gross losses from sales (4 ) (15 ) Net gains (losses) from redemptions (2 ) (28 ) Other-than-temporary impairment losses 0 (4 ) Total fixed maturity securities 3 (35 ) Equity securities (2) (46 ) (1) 19 (3) Loan loss reserves (7 ) (1 ) Derivatives and other: Derivative gains (losses) 144 (52 ) Foreign currency gains (losses) (228 ) (71 ) Total derivatives and other (84 ) (123 ) Total realized investment gains (losses) $ (134 ) $ (140 ) (1) Includes perpetual securities (2) See Note 1 of the Notes to the Consolidated Financial Statements for the adoption of accounting guidance on January 1, 2018 related to financial instruments. (3) Includes $6 of impairments The unrealized holding losses, net of gains, recorded as a component of realized investment gains and losses for the three-month period ended March 31, 2018, that relates to equity securities still held at the March 31, 2018, reporting date was $43 million . Unrealized Investment Gains and Losses Effect on Shareholders’ Equity The net effect on shareholders’ equity of unrealized gains and losses from investment securities was as follows: (In millions) March 31, 2018 December 31, Unrealized gains (losses) on securities available for sale $ 7,426 $ 9,358 Deferred income taxes (2,220 ) (3,394 ) Shareholders’ equity, unrealized gains (losses) on investment securities $ 5,206 $ 5,964 See Note 1 for discussion of the accounting treatment of tax on amounts recorded in accumulated other comprehensive income pursuant to the Tax Act and for the adoption of accounting guidance on January 1, 2018 related to financial instruments. Gross Unrealized Loss Aging The following tables show the fair values and gross unrealized losses of the Company's available-for-sale and held-to-maturity investments that were in an unrealized loss position, aggregated by investment category and length of time that individual securities have been in a continuous unrealized loss position. March 31, 2018 Total Less than 12 months 12 months or longer (In millions) Fair Unrealized Fair Unrealized Fair Unrealized Fixed maturity securities: (1) U.S. government and U.S. dollar-denominated $ 79 $ 1 $ 71 $ 1 $ 8 $ 0 Japan government and Yen-denominated 4,054 192 128 0 3,926 192 Municipalities: Yen-denominated 128 11 0 0 128 11 Mortgage- and asset- U.S. dollar-denominated 91 1 71 1 20 0 Public utilities: U.S. dollar-denominated 1,649 107 1,095 52 554 55 Yen-denominated 90 4 0 0 90 4 Sovereign and supranational: Yen-denominated 302 27 302 27 0 0 Banks/financial institutions: U.S. dollar-denominated 685 34 596 28 89 6 Yen-denominated 1,467 89 645 14 822 75 Other corporate: U.S. dollar-denominated 13,730 1,111 8,903 420 4,827 691 Yen-denominated 302 8 276 6 26 2 Total $ 22,577 $ 1,585 $ 12,087 $ 549 $ 10,490 $ 1,036 (1) Includes perpetual securities December 31, 2017 Total Less than 12 months 12 months or longer (In millions) Fair Unrealized Fair Unrealized Fair Unrealized Fixed maturity securities: (1) U.S. government and U.S. dollar-denominated $ 74 $ 1 $ 74 $ 1 $ 0 $ 0 Japan government and Yen-denominated 5,255 271 1,264 9 3,991 262 Municipalities: Yen-denominated 129 12 10 0 119 12 Public utilities: U.S. dollar-denominated 785 27 221 3 564 24 Yen-denominated 83 6 0 0 83 6 Sovereign and supranational: Yen-denominated 309 1 309 1 0 0 Banks/financial institutions: U.S. dollar-denominated 362 8 316 5 46 3 Yen-denominated 1,507 62 394 4 1,113 58 Other corporate: U.S. dollar-denominated 7,741 418 2,839 50 4,902 368 Yen-denominated 440 7 349 4 91 3 Total $ 16,685 $ 813 $ 5,776 $ 77 $ 10,909 $ 736 (1) Includes perpetual securities Analysis of Securities in Unrealized Loss Positions The unrealized losses on the Company's fixed maturity securities investments have been primarily related to general market changes in interest rates, foreign exchange rates, and/or the levels of credit spreads rather than specific concerns with the issuer's ability to pay interest and repay principal. For any significant declines in fair value of its fixed maturity securities, the Company performs a more focused review of the related issuers' credit profile. For corporate issuers, the Company evaluates their assets, business profile including industry dynamics and competitive positioning, financial statements and other available financial data. For non-corporate issuers, the Company analyzes all sources of credit support, including issuer-specific factors. The Company utilizes information available in the public domain and, for certain private placement issuers, from consultations with the issuers directly. The Company also considers ratings from Nationally Recognized Statistical Rating Organizations (NRSROs), as well as the specific characteristics of the security it owns including seniority in the issuer's capital structure, covenant predictions, or other relevant features. From these reviews, the Company evaluates the issuers' continued ability to service the Company's investment through payment of interest and principal. Assuming no credit-related factors develop, unrealized gains and losses on fixed maturity securities are expected to diminish as investments near maturity. Based on its credit analysis, the Company believes that the issuers of its fixed maturity investments in the sectors shown in the table above have the ability to service their obligations to the Company. Other Investments The table below reflects the composition of the carrying value for other investments as of the periods presented. (In millions) March 31, 2018 December 31, 2017 Other investments: Transitional real estate loans $ 2,719 $ 1,235 Commercial mortgage loans 917 908 Middle market loans 957 859 Policy loans 227 210 Short-term investments 0 57 Other 253 133 Total other investments $ 5,073 $ 3,402 Loans and Loan Receivables The Company classifies its transitional real estate loans (TREs), commercial mortgage loans (CMLs) and middle market loans (MMLs) as held-for-investment and includes them in the other investments line on the consolidated balance sheets. The Company carries them on the balance sheet at amortized cost less an estimated allowance for loan losses. The Company's allowance for loan losses is established using both general and specific allowances. The general allowance is used for loans grouped by similar risk characteristics where a loan-specific or market-specific risk has not been identified, but for which the Company estimates probable incurred losses. The specific allowance is used on an individual loan basis when it is probable that a loss has been incurred. As of March 31, 2018 , and December 31, 2017 , the Company's allowance for loan losses was $18 million and $11 million , respectively. As of March 31, 2018 , and December 31, 2017 , the Company had no loans that were past due in regards to principal and/or interest payments. Additionally, the Company held no loans that were on nonaccrual status or considered impaired as of March 31, 2018 , and December 31, 2017 . The Company had no troubled debt restructurings during the three months ended March 31, 2018 and 2017. Transitional Real Estate Loans Transitional real estate loans are commercial mortgage loans that are typically relatively short-term floating rate instruments secured by a first lien on the property. These loans provide funding for properties undergoing a change in their physical characteristics and/or economic profile. As of March 31, 2018 , the Company had $436 million in outstanding commitments to fund transitional real estate loans. These commitments are contingent on the final underwriting and due diligence to be performed. Commercial Mortgage Loans As of March 31, 2018 , the Company had $54 million in outstanding commitments to fund commercial mortgage loans. These commitments are contingent on the final underwriting and due diligence to be performed. Middle Market Loans Middle market loans are generally considered to be below investment grade. The carrying value for middle market loans included an unfunded amount of $76 million and $109 million , as of March 31, 2018 , and December 31, 2017 , respectively, that is reflected in other liabilities on the consolidated balance sheets. As of March 31, 2018 , the Company had commitments of approximately $985 million to fund potential future loan originations related to this investment program. These commitments are contingent upon the availability of middle market loans that meet the Company's underwriting criteria. Other Other investments primarily includes investments in limited partnerships. As of March 31, 2018 , the Company had $763 million in outstanding commitments to fund alternative investments in limited partnerships. Variable Interest Entities (VIEs) As a condition of its involvement or investment in a VIE, the Company enters into certain protective rights and covenants that preclude changes in the structure of the VIE that would alter the creditworthiness of the Company's investment or its beneficial interest in the VIE. For those VIEs other than certain unit trust structures, the Company's involvement is passive in nature. The Company has not, nor has it been, required to purchase any securities issued in the future by these VIEs. The Company's ownership interest in VIEs is limited to holding the obligations issued by them. The Company has no direct or contingent obligations to fund the limited activities of these VIEs, nor does it have any direct or indirect financial guarantees related to the limited activities of these VIEs. The Company has not provided any assistance or any other type of financing support to any of the VIEs it invests in, nor does it have any intention to do so in the future. For those VIEs in which the Company holds debt obligations, the weighted-average lives of the Company's notes are very similar to the underlying collateral held by these VIEs where applicable. The Company's risk of loss related to its interests in any of its VIEs is limited to the carrying value of the related investments held in the VIE. VIEs - Consolidated The following table presents the cost or amortized cost, fair value and balance sheet caption in which the assets and liabilities of consolidated VIEs are reported. Investments in Consolidated Variable Interest Entities March 31, 2018 December 31, 2017 (In millions) Cost or Amortized Fair Cost or Amortized Fair Assets: Fixed maturity securities, available for sale (1) $ 4,695 $ 5,431 $ 4,538 $ 5,509 Equity securities 760 760 606 753 Other investments (2) 3,994 3,974 2,341 2,328 Other assets (3) 241 241 151 151 Total assets of consolidated VIEs $ 9,690 $ 10,406 $ 7,636 $ 8,741 Liabilities: Other liabilities (3) $ 86 $ 86 $ 128 $ 128 Total liabilities of consolidated VIEs $ 86 $ 86 $ 128 $ 128 (1) Includes perpetual securities (2) Consists of TREs, CMLs, MMLs, and alternative investments in limited partnerships (3) Consists entirely of derivatives The Company is substantively the only investor in the consolidated VIEs listed in the table above. As the sole investor in these VIEs, the Company has the power to direct the activities of a variable interest entity that most significantly impact the entity's economic performance and is therefore considered to be the primary beneficiary of the VIEs that it consolidates. The Company also participates in substantially all of the variability created by these VIEs. The activities of these VIEs are limited to holding invested assets and foreign currency, and/or credit default swaps (CDS), as appropriate, and utilizing the cash flows from these securities to service its investment. Neither the Company nor any of its creditors are able to obtain the underlying collateral of the VIEs unless there is an event of default or other specified event. For those VIEs that contain a swap, the Company is not a direct counterparty to the swap contracts and has no control over them. The Company's loss exposure to these VIEs is limited to its original investment. The Company's consolidated VIEs do not rely on outside or ongoing sources of funding to support their activities beyond the underlying collateral and swap contracts, if applicable. With the exception of its investment in unit trust structures, the underlying collateral assets and funding of the Company's consolidated VIEs are generally static in nature and the underlying collateral and the reference corporate entities covered by any CDS contracts were all investment grade at the time of issuance. Investments in Unit Trust Structures The Company also utilizes unit trust structures in its Aflac Japan segment to invest in various asset classes. As the sole investor of these VIEs, the Company is required to consolidate these trusts under U.S. GAAP. VIEs-Not Consolidated The table below reflects the amortized cost, fair value and balance sheet caption in which the Company's investment in VIEs not consolidated are reported. Investments in Variable Interest Entities Not Consolidated March 31, 2018 December 31, 2017 (In millions) Amortized Fair Amortized Fair Assets: Fixed maturity securities, available for sale (1) $ 5,194 $ 5,749 $ 5,004 $ 5,724 Fixed maturity securities, held to maturity 2,711 3,077 2,549 2,929 Other investments 110 108 55 55 Total investments in VIEs not consolidated $ 8,015 $ 8,934 $ 7,608 $ 8,708 (1) Includes perpetual securities The Company holds alternative investments in limited partnerships that have been determined to be VIEs. These partnerships invest in private equity and structured investments. The Company’s maximum exposure to loss on these investments is limited to the amount of its investment. The Company is not the primary beneficiary of these VIEs and is therefore not required to consolidate them. The Company classifies these investments as Other investments in the consolidated balance sheets. Certain investments in VIEs that the Company is not required to consolidate are investments that are in the form of debt obligations from the VIEs that are irrevocably and unconditionally guaranteed by their corporate parents or sponsors. These VIEs are the primary financing vehicles used by their corporate sponsors to raise financing in the capital markets. The variable interests created by these VIEs are principally or solely a result of the debt instruments issued by them. The Company does not have the power to direct the activities that most significantly impact the entity's economic performance, nor does it have the obligation to absorb losses of the entity or the right to receive benefits from the entity. As such, the Company is not the primary beneficiary of these VIEs and is therefore not required to consolidate them. Securities Lending and Pledged Securities The Company lends fixed maturity and public equity securities to financial institutions in short-term security-lending transactions. These short-term security-lending arrangements increase investment income with minimal risk. The Company's security lending policy requires that the fair value of the securities and/or unrestricted cash received as collateral be 102% or more of the fair value of the loaned securities. These securities continue to be carried as investment assets on the Company's balance sheet during the terms of the loans and are not reported as sales. The Company receives cash or other securities as collateral for such loans. For loans involving unrestricted cash or securities as collateral, the collateral is reported as an asset with a corresponding liability for the return of the collateral. Details of the Company's securities lending activities were as follows: Securities Lending Transactions Accounted for as Secured Borrowings March 31, 2018 Remaining Contractual Maturity of the Agreements (In millions) Overnight (1) Up to 30 Total Securities lending transactions: Fixed maturity securities: Japan government and agencies $ 0 $ 4,894 $ 4,894 Public utilities 30 0 30 Banks/financial institutions 52 0 52 Other corporate 384 0 384 Equity securities 8 0 8 Total borrowings $ 474 $ 4,894 $ 5,368 Gross amount of recognized liabilities for securities lending transactions $ 5,368 Amounts related to agreements not included in offsetting disclosure in Note 4 $ 0 (1) These securities are pledged as collateral under the Company's U.S. securities lending program and can be called at its discretion; therefore, they are classified as Overnight and Continuous. Securities Lending Transactions Accounted for as Secured Borrowings December 31, 2017 Remaining Contractual Maturity of the Agreements (In millions) Overnight (1) Up to 30 Total Securities lending transactions: Fixed maturity securities: Japan government and agencies $ 0 $ 49 $ 49 Public utilities 73 0 73 Banks/financial institutions 54 0 54 Other corporate 415 0 415 Equity securities 15 0 15 Total borrowings $ 557 $ 49 $ 606 Gross amount of recognized liabilities for securities lending transactions $ 606 Amounts related to agreements not included in offsetting disclosure in Note 4 $ 0 (1) These securities are pledged as collateral under the Company's U.S. securities lending program and can be called at its discretion; therefore, they are classified as Overnight and Continuous. The Company did not have any repurchase agreements or repurchase-to-maturity transactions outstanding as of March 31, 2018 , and December 31, 2017 , respectively. Certain fixed maturity securities can be pledged as collateral as part of derivative transactions, or pledged to support state deposit requirements or certain investment programs. For additional information regarding pledged securities related to derivative transactions, see Note 4.

DERIVATIVE INSTRUMENTS

DERIVATIVE INSTRUMENTS	3 Months Ended
	Mar. 31, 2018
Derivative Instruments and Hedging Activities Disclosure [Abstract]
DERIVATIVE INSTRUMENTS	DERIVATIVE INSTRUMENTS The Company's freestanding derivative financial instruments have historically consisted of: (1) foreign currency forwards and options used in hedging foreign exchange risk on U.S. dollar-denominated investments in Aflac Japan's portfolio; (2) foreign currency forwards and options used to hedge foreign exchange risk from the Company's net investment in Aflac Japan and economically hedge certain portions of forecasted cash flows denominated in yen; (3) swaps associated with the Company's notes payable, consisting of cross-currency interest rate swaps, also referred to as foreign currency swaps, associated with certain senior notes and its subordinated debentures; and (4) foreign currency swaps and credit default swaps that are associated with investments in special-purpose entities, including VIEs where the Company is the primary beneficiary. The Company does not use derivative financial instruments for trading purposes, nor does it engage in leveraged derivative transactions. Some of the Company's derivatives are designated as cash flow hedges, fair value hedges or net investment hedges; however, other derivatives do not qualify for hedge accounting or the Company elects not to designate them as an accounting hedge. The Company utilizes a net investment hedge to mitigate foreign exchange exposure resulting from its net investment in Aflac Japan. In addition to designating derivatives as hedging instruments, the Company has designated the majority of the Parent Company's yen-denominated liabilities (notes payable and loans) as nonderivative hedging instruments for this net investment hedge. Derivative Types Foreign currency forwards and options are executed for the Aflac Japan segment in order to hedge the currency risk on the carrying value of certain U.S. dollar-denominated investments. The average maturity of these forwards and options can change depending on factors such as market conditions and types of investments being held. In situations where the maturity of the forwards and options are shorter than the underlying investment being hedged, the Company may enter into new forwards and options near maturity of the existing derivative in order to continue hedging the underlying investment. In forward transactions, Aflac Japan agrees with another party to buy a fixed amount of yen and sell a corresponding amount of U.S. dollars at a specified future date. Aflac Japan also executes foreign currency option transactions in a collar strategy, where Aflac Japan agrees with another party to simultaneously purchase a fixed amount of U.S. dollar put options and sell U.S. dollar call options. The combination of these two actions results in no net premium being paid (i.e. a costless or zero-cost collar). The foreign currency forwards and options are used in fair value hedging relationships to mitigate the foreign exchange risk associated with U.S. dollar-denominated investments supporting yen-denominated liabilities. Foreign currency forwards and options are also used to hedge the currency risk associated with the net investment in Aflac Japan. In these forward transactions, Aflac agrees with another party to buy a fixed amount of U.S. dollars and sell a corresponding amount of yen at a specified price at a specified future date. In the option transactions, the Company uses a combination of foreign currency options to protect expected future cash flows by simultaneously purchasing yen put options (options that protect against a weakening yen) and selling yen call options (options that limit participation in a strengthening yen). The combination of these two actions results in no net premium being paid (i.e. a costless or zero-cost collar). The Company enters into foreign currency swaps pursuant to which it exchanges an initial principal amount in one currency for an initial principal amount of another currency, with an agreement to re-exchange the currencies at a future date at an agreed upon exchange rate. There may also be periodic exchanges of payments at specified intervals based on the agreed upon rates and notional amounts. Foreign currency swaps are used primarily in the consolidated VIEs in the Company's Aflac Japan portfolio to convert foreign-denominated cash flows to yen, the functional currency of Aflac Japan, in order to minimize cash flow fluctuations. The Company also uses foreign currency swaps to economically convert certain of its U.S. dollar-denominated senior note and subordinated debenture principal and interest obligations into yen-denominated obligations. The only CDS that the Company currently holds relates to components of an investment in a VIE and is used to assume credit risk related to an individual security. This CDS contract entitles the consolidated VIE to receive periodic fees in exchange for an obligation to compensate the derivative counterparties should the referenced security issuer experience a credit event, as defined in the contract. Periodically, the Company may enter into other derivative transactions depending on general economic conditions. Derivative Balance Sheet Classification The tables below summarize the balance sheet classification of the Company's derivative fair value amounts, as well as the gross asset and liability fair value amounts. The fair value amounts presented do not include income accruals. The notional amount of derivative contracts represents the basis upon which pay or receive amounts are calculated and are not reflective of exposure or credit risk. March 31, 2018 December 31, 2017 (In millions) Asset Liability Asset Liability Hedge Designation/ Derivative Notional Fair Value Fair Value Notional Fair Value Fair Value Cash flow hedges: Foreign currency swaps $ 75 $ 1 $ (2 ) $ 75 $ 0 $ (8 ) Total cash flow hedges 75 1 (2 ) 75 0 (8 ) Fair value hedges: Foreign currency forwards 5,550 244 (5 ) 7,640 2 (221 ) Foreign currency options 9,120 0 (3 ) 7,670 0 (2 ) Total fair value hedges 14,670 244 (8 ) 15,310 2 (223 ) Net investment hedge: Foreign currency forwards 0 0 0 5 0 0 Foreign currency options 0 0 0 434 12 (1 ) Total net investment hedge 0 0 0 439 12 (1 ) Non-qualifying strategies: Foreign currency swaps 5,426 369 (263 ) 5,386 296 (189 ) Foreign currency forwards 6,656 182 (80 ) 3,683 20 (53 ) Foreign currency options 299 0 0 770 0 0 Credit default swaps 94 1 0 88 1 0 Total non-qualifying strategies 12,475 552 (343 ) 9,927 317 (242 ) Total derivatives $ 27,220 $ 797 $ (353 ) $ 25,751 $ 331 $ (474 ) Balance Sheet Location Other assets $ 18,248 $ 797 $ 0 $ 10,948 $ 331 $ 0 Other liabilities 8,972 0 (353 ) 14,803 0 (474 ) Total derivatives $ 27,220 $ 797 $ (353 ) $ 25,751 $ 331 $ (474 ) Cash Flow Hedges Certain of the Company's consolidated VIEs have foreign currency swaps that qualify for hedge accounting treatment. For those that have qualified, the Company has designated the derivative as a hedge of the variability in cash flows of a forecasted transaction or of amounts to be received or paid related to a recognized asset (“cash flow” hedge). The maximum length of time for which these cash flows are hedged is nine years. The remaining derivatives in the Company's consolidated VIEs that have not qualified for hedge accounting are included in “non-qualifying strategies.” Fair Value Hedges The Company designates and accounts for certain foreign currency forwards and options as fair value hedges when they meet the requirements for hedge accounting. These foreign currency forwards and options hedge the foreign currency exposure of certain U.S. dollar-denominated investments. The Company recognizes gains and losses on these derivatives and the related hedged items in current earnings within derivative and other gains (losses). The change in the fair value of the foreign currency forwards related to the changes in the difference between the spot rate and the forward price is excluded from the assessment of hedge effectiveness. The change in fair value of the foreign currency option related to the time value of the option is excluded from the assessment of hedge effectiveness. The following table presents the gains and losses on derivatives and the related hedged items in fair value hedges. Fair Value Hedging Relationships (In millions) Hedging Derivatives Hedged Items Hedging Derivatives Hedged Items Total Gains (Losses) Gains (Losses) Gains (Losses) Ineffectiveness Three Months Ended March 31, 2018: Foreign currency Fixed maturity securities $ 414 $ (39 ) $ 453 $ (464 ) $ (11 ) Foreign currency Fixed maturity securities (1 ) (1 ) 0 0 0 Three Months Ended March 31, 2017: Foreign currency forwards Fixed maturity and equity securities $ 341 $ (48 ) $ 389 $ (372 ) $ 17 Foreign currency options Fixed maturity securities 24 13 11 (10 ) 1 Net Investment Hedge The Company's investment in Aflac Japan is affected by changes in the yen/dollar exchange rate. To mitigate this exposure, the Parent Company's yen-denominated liabilities (see Note 8) have been designated as non-derivative hedges and foreign currency forwards and options have been designated as derivative hedges of the foreign currency exposure of the Company's net investment in Aflac Japan. The Company's net investment hedge was effective during the three -month periods ended March 31, 2018 and 2017 , respectively. Non-qualifying Strategies For the Company's derivative instruments in consolidated VIEs that do not qualify for hedge accounting treatment, all changes in their fair value are reported in current period earnings within derivative and other gains (losses). The amount of gain or loss recognized in earnings for the Company's VIEs is attributable to the derivatives in those investment structures. While the change in value of the swaps is recorded through current period earnings, the change in value of the available-for-sale fixed maturity securities associated with these swaps is recorded through other comprehensive income. As of March 31, 2018 , the Parent Company had cross-currency interest rate swap agreements related to its $550 million senior notes due March 2020, $350 million senior notes due February 2022, $700 million senior notes due June 2023, $750 million senior notes due November 2024 and $450 million senior notes due March 2025. Changes in the values of these swaps are recorded through current period earnings. For additional information regarding these swaps, see Note 8 in this report and Note 9 of the Notes to the Consolidated Financial Statements in the 2017 Annual Report. The Company uses foreign exchange forwards and options to mitigate the currency risk of some of its U.S. dollar-denominated loan receivables held within the Aflac Japan segment. The Company has not elected to apply hedge accounting for these loan receivables due to the change in fair value of the foreign exchange forwards and the foreign currency remeasurement of the loan receivables being recorded through current period earnings, and generally offsetting each other within realized investment gains (losses). In order to economically mitigate currency risk of future yen dividends from Aflac Japan while lowering consolidated hedge costs associated with Aflac Japan's U.S. dollar investment hedging, starting in the first quarter of 2018, the Parent Company began entering into offsetting hedge positions using foreign exchange forwards and options. This activity is reported in the Corporate and other segment. Impact of Derivatives and Hedging Instruments The following table summarizes the impact to realized investment gains (losses) and other comprehensive income (loss) from all derivatives and hedging instruments. Three Months Ended March 31, 2018 2017 (In millions) Realized Investment Other (1) Realized Investment Other (1) Qualifying hedges: Cash flow hedges: Foreign currency swaps $ 1 $ 6 $ 0 $ 2 Total cash flow hedges 1 6 0 2 Fair value hedges: Foreign currency forwards (2) (50 ) 0 (31 ) 0 Foreign currency options (2) (1 ) 0 14 0 Total fair value hedges (51 ) 0 (17 ) 0 Net investment hedge: Non-derivative hedging instruments 0 (84 ) 0 (17 ) Foreign currency forwards 0 0 0 (9 ) Foreign currency options 0 (8 ) 0 (23 ) Total net investment hedge 0 (92 ) 0 (49 ) Non-qualifying strategies: Foreign currency swaps 14 0 (8 ) 0 Foreign currency forwards 179 0 (27 ) 0 Foreign currency options 1 0 0 0 Total non-qualifying strategies 194 0 (35 ) 0 Total $ 144 $ (86 ) $ (52 ) $ (47 ) (1) Cash flow hedge items are recorded as unrealized gains (losses) on derivatives and net investment hedge items are recorded in the unrealized foreign currency translation gains (losses) line in the consolidated statement of comprehensive income (loss). (2) Impact shown net of effect of hedged items (see Fair Value Hedges section of this Note 4 for further detail) The Company reclassified an immaterial amount related to its cash flow hedges from accumulated other comprehensive income (loss) into earnings for the three -month periods ended March 31, 2018 and 2017. There was no gain or loss reclassified from accumulated other comprehensive income (loss) into earnings related to the net investment hedge for the three -month periods ended March 31, 2018 and 2017 . As of March 31, 2018 , deferred gains and losses on derivative instruments recorded in accumulated other comprehensive income that are expected to be reclassified to earnings during the next twelve months were immaterial. Credit Risk Assumed through Derivatives For the foreign currency and credit default swaps associated with the Company's VIE investments for which it is the primary beneficiary, the Company bears the risk of loss due to counterparty default even though it is not a direct counterparty to those contracts. The Company is a direct counterparty to the foreign currency swaps that it has entered into in connection with certain of its senior notes and subordinated debentures; foreign currency forwards; foreign currency options; and interest rate swaptions, and therefore the Company is exposed to credit risk in the event of nonperformance by the counterparties in those contracts. The risk of counterparty default for the Company's foreign currency swaps, certain foreign currency forwards, foreign currency options and interest rate swaptions is mitigated by collateral posting requirements that counterparties to those transactions must meet. As of March 31, 2018 , there were 15 counterparties to the Company's derivative agreements, with four comprising 59% of the aggregate notional amount. The counterparties to these derivatives are financial institutions with the following credit ratings: March 31, 2018 December 31, 2017 (In millions) Notional Amount Asset Derivatives Liability Derivatives Notional Amount Asset Derivatives Liability Derivatives Counterparties' credit rating: AA $ 4,685 $ 123 $ (12 ) $ 4,708 $ 52 $ (37 ) A 22,081 673 (290 ) 20,604 271 (370 ) BBB 454 1 (51 ) 439 8 (67 ) Total $ 27,220 $ 797 $ (353 ) $ 25,751 $ 331 $ (474 ) The Company engages in derivative transactions directly with unaffiliated third parties under International Swaps and Derivatives Association, Inc. (ISDA) agreements and other documentation. Most of the ISDA agreements also include Credit Support Annexes (CSAs) provisions, which generally provide for two-way collateral postings at the first dollar of exposure. The Company mitigates the risk that counterparties to transactions might be unable to fulfill their contractual obligations by monitoring counterparty credit exposure and collateral value while generally requiring that collateral be posted at the outset of the transaction. In addition, a significant portion of the derivative transactions have provisions that give the counterparty the right to terminate the transaction upon a downgrade of Aflac’s financial strength rating. The actual amount of payments that the Company could be required to make depends on market conditions, the fair value of outstanding affected transactions, and other factors prevailing at and after the time of the downgrade. Collateral posted by the Company to third parties for derivative transactions can generally be repledged or resold by the counterparties. The aggregate fair value of all derivative instruments with credit-risk-related contingent features that were in a net liability position by counterparty was approximately $154 million and $264 million as of March 31, 2018 , and December 31, 2017 , respectively. If the credit-risk-related contingent features underlying these agreements had been triggered on March 31, 2018 , the Company estimates that it would be required to post a maximum of $5 million of additional collateral to these derivative counterparties. The Company is generally allowed to sell or repledge collateral obtained from its derivative counterparties, although it does not typically exercise such rights. (See the Offsetting tables below for collateral posted or received as of the reported balance sheet dates.) Offsetting of Financial Instruments and Derivatives Most of the Company's derivative instruments are subject to enforceable master netting arrangements that provide for the net settlement of all derivative contracts between the Parent Company or Aflac and its respective counterparty in the event of default or upon the occurrence of certain termination events. Collateral support agreements with the master netting arrangements generally provide that the Company will receive or pledge financial collateral at the first dollar of exposure. The Company has securities lending agreements with unaffiliated financial institutions that post collateral to the Company in return for the use of its fixed maturity and public equity securities (see Note 3). When the Company has entered into securities lending agreements with the same counterparty, the agreements generally provide for net settlement in the event of default by the counterparty. This right of set-off allows the Company to keep and apply collateral received if the counterparty failed to return the securities borrowed from the Company as contractually agreed. The tables below summarize the Company's derivatives and securities lending transactions, and as reflected in the tables, in accordance with U.S. GAAP, the Company's policy is to not offset these financial instruments in the Consolidated Balance Sheets. Offsetting of Financial Assets and Derivative Asset March 31, 2018 Gross Amounts Not Offset (In millions) Gross Amount of Recognized Assets Gross Amount Offset in Balance Sheet Net Amount of Assets Presented in Balance Sheet Financial Instruments Securities Collateral Cash Collateral Received Net Amount Derivative assets: Derivative assets subject to a master netting agreement or offsetting arrangement $ 556 $ 0 $ 556 $ (116 ) $ (343 ) $ (67 ) $ 30 Derivative assets not subject to a master netting agreement or offsetting arrangement 241 241 241 Total derivative assets 797 0 797 (116 ) (343 ) (67 ) 271 Securities lending and similar arrangements 5,249 0 5,249 0 0 (5,249 ) 0 Total $ 6,046 $ 0 $ 6,046 $ (116 ) $ (343 ) $ (5,316 ) $ 271 December 31, 2017 Gross Amounts Not Offset (In millions) Gross Amount of Recognized Assets Gross Amount Offset in Balance Sheet Net Amount of Assets Presented in Balance Sheet Financial Instruments Securities Collateral Cash Collateral Received Net Amount Derivative assets: Derivative assets subject to a master netting agreement or offsetting arrangement $ 180 $ 0 $ 180 $ (82 ) $ 0 $ (98 ) $ 0 Derivative assets not subject to a master netting agreement or offsetting arrangement 151 151 151 Total derivative assets 331 0 331 (82 ) 0 (98 ) 151 Securities lending and similar arrangements 592 0 592 0 0 (592 ) 0 Total $ 923 $ 0 $ 923 $ (82 ) $ 0 $ (690 ) $ 151 Offsetting of Financial Liabilities and Derivative Liabilities March 31, 2018 Gross Amounts Not Offset (In millions) Gross Amount of Recognized Liabilities Gross Amount Offset in Balance Sheet Net Amount of Liabilities Presented in Balance Sheet Financial Instruments Securities Collateral Cash Collateral Pledged Net Amount Derivative liabilities: Derivative liabilities subject to a master netting agreement or offsetting arrangement $ (267 ) $ 0 $ (267 ) $ 116 $ 36 $ 113 $ (2 ) Derivative liabilities not subject to a master netting agreement or offsetting arrangement (86 ) (86 ) (86 ) Total derivative liabilities (353 ) 0 (353 ) 116 36 113 (88 ) Securities lending and similar arrangements (5,368 ) 0 (5,368 ) 5,249 0 0 (119 ) Total $ (5,721 ) $ 0 $ (5,721 ) $ 5,365 $ 36 $ 113 $ (207 ) December 31, 2017 Gross Amounts Not Offset (In millions) Gross Amount of Recognized Liabilities Gross Amount Offset in Balance Sheet Net Amount of Liabilities Presented in Balance Sheet Financial Instruments Securities Collateral Cash Collateral Pledged Net Amount Derivative liabilities: Derivative liabilities subject to a master netting agreement or offsetting arrangement $ (346 ) $ 0 $ (346 ) $ 82 $ 245 $ 10 $ (9 ) Derivative liabilities not subject to a master netting agreement or offsetting arrangement (128 ) (128 ) (128 ) Total derivative liabilities (474 ) 0 (474 ) 82 245 10 (137 ) Securities lending and similar arrangements (606 ) 0 (606 ) 592 0 0 (14 ) Total $ (1,080 ) $ 0 $ (1,080 ) $ 674 $ 245 $ 10 $ (151 ) For additional information on the Company's financial instruments, see the accompanying Notes 1, 3 and 5 and Notes 1, 3 and 5 of the Notes to the Consolidated Financial Statements in the 2017 Annual Report.

FAIR VALUE MEASUREMENTS

FAIR VALUE MEASUREMENTS	3 Months Ended
	Mar. 31, 2018
Fair Value Disclosures [Abstract]
FAIR VALUE MEASUREMENTS	FAIR VALUE MEASUREMENTS Fair Value Hierarchy U.S. GAAP specifies a hierarchy of valuation techniques based on whether the inputs to those valuation techniques are observable or unobservable. These two types of inputs create three valuation hierarchy levels. Level 1 valuations reflect quoted market prices for identical assets or liabilities in active markets. Level 2 valuations reflect quoted market prices for similar assets or liabilities in an active market, quoted market prices for identical or similar assets or liabilities in non-active markets or model-derived valuations in which all significant valuation inputs are observable in active markets. Level 3 valuations reflect valuations in which one or more of the significant inputs are not observable in an active market. The following tables present the fair value hierarchy levels of the Company's assets and liabilities that are measured and carried at fair value on a recurring basis. March 31, 2018 (In millions) Quoted Prices in Significant Significant Total Assets: Securities available for sale, carried at Fixed maturity securities: (1) Government and agencies $ 35,325 $ 1,411 $ 0 $ 36,736 Municipalities 0 1,373 0 1,373 Mortgage- and asset-backed securities 0 269 186 455 Public utilities 0 7,724 83 7,807 Sovereign and supranational 0 1,866 0 1,866 Banks/financial institutions 0 9,120 24 9,144 Other corporate 0 31,509 143 31,652 Total fixed maturity securities 35,325 53,272 436 89,033 (1) Equity securities (1) 1,015 77 16 1,108 (1) Cash and cash equivalents 4,080 0 0 4,080 Other assets: Foreign currency swaps 0 130 240 370 Foreign currency forwards 0 426 0 426 Credit default swaps 0 0 1 1 Total other assets 0 556 241 797 Total assets $ 40,420 $ 53,905 $ 693 $ 95,018 Liabilities: Other liabilities: Foreign currency swaps $ 0 $ 179 $ 86 $ 265 Foreign currency forwards 0 85 0 85 Foreign currency options 0 3 0 3 Total liabilities $ 0 $ 267 $ 86 $ 353 (1) Includes perpetual securities December 31, 2017 (In millions) Quoted Prices in Significant Significant Total Assets: Securities available for sale, carried at Fixed maturity securities: (1) Government and agencies $ 30,109 $ 1,121 $ 0 $ 31,230 Municipalities 0 1,370 0 1,370 Mortgage- and asset-backed securities 0 269 175 444 Public utilities 0 7,886 68 7,954 Sovereign and supranational 0 1,909 0 1,909 Banks/financial institutions 0 8,908 25 8,933 Other corporate 0 32,327 146 32,473 Total fixed maturity securities 30,109 53,790 414 84,313 (1) Equity securities 1,001 6 16 1,023 Other investments 57 0 0 57 Cash and cash equivalents 3,491 0 0 3,491 Other assets: Foreign currency swaps 0 146 150 296 Foreign currency forwards 0 22 0 22 Foreign currency options 0 12 0 12 Credit default swaps 0 0 1 1 Total other assets 0 180 151 331 Total assets $ 34,658 $ 53,976 $ 581 $ 89,215 Liabilities: Other liabilities: Foreign currency swaps $ 0 $ 69 $ 128 $ 197 Foreign currency forwards 0 274 0 274 Foreign currency options 0 3 0 3 Total liabilities $ 0 $ 346 $ 128 $ 474 (1) Includes perpetual securities The following tables present the carrying amount and fair value categorized by fair value hierarchy level for the Company's financial instruments that are not carried at fair value. March 31, 2018 (In millions) Carrying Quoted Prices in Significant Significant Total Assets: Securities held to maturity, Fixed maturity securities: Government and agencies $ 22,686 $ 28,317 $ 0 $ 0 $ 28,317 Municipalities 379 0 493 0 493 Mortgage and asset-backed 26 0 9 19 28 Public utilities 3,508 0 3,891 0 3,891 Sovereign and 1,620 0 1,919 0 1,919 Banks/financial institutions 2,300 0 2,477 0 2,477 Other corporate 2,858 0 3,343 0 3,343 Other investments (1) 4,608 0 15 4,575 4,590 Total assets $ 37,985 $ 28,317 $ 12,147 $ 4,594 $ 45,058 Liabilities: Other policyholders’ funds $ 7,417 $ 0 $ 0 $ 7,307 $ 7,307 Notes payable 5,352 0 5,146 281 5,427 Total liabilities $ 12,769 $ 0 $ 5,146 $ 7,588 $ 12,734 (1) Excludes policy loans of $227 and equity method investments of $238 , at carrying value December 31, 2017 (In millions) Carrying Quoted Prices in Significant Significant Total Assets: Securities held to maturity, Fixed maturity securities: Government and agencies $ 21,331 $ 26,491 $ 0 $ 0 $ 26,491 Municipalities 357 0 462 0 462 Mortgage and asset-backed 26 0 8 19 27 Public utilities 3,300 0 3,698 0 3,698 Sovereign and 1,523 0 1,835 0 1,835 Banks/financial institutions 2,206 0 2,387 0 2,387 Other corporate 2,687 0 3,172 0 3,172 Other investments (1) 3,017 0 15 2,987 3,002 Total assets $ 34,447 $ 26,491 $ 11,577 $ 3,006 $ 41,074 Liabilities: Other policyholders’ funds $ 6,939 $ 0 $ 0 $ 6,841 $ 6,841 Notes payable 5,267 0 5,288 265 5,553 Total liabilities $ 12,206 $ 0 $ 5,288 $ 7,106 $ 12,394 (1) Excludes policy loans of $210 and equity method investments of $118 , at carrying value Fair Value of Financial Instruments Fixed maturity and equity securities The Company determines the fair values of fixed maturity securities and public and privately-issued equity securities using the following approaches or techniques: price quotes and valuations from third party pricing vendors (including quoted market prices readily available from public exchange markets) and non-binding price quotes the Company obtains from outside brokers. A third party pricing vendor has developed valuation models to determine fair values of privately issued securities to reflect the impact of the persistent economic environment and the changing regulatory framework. These models are discounted cash flow (DCF) valuation models, but also use information from related markets, specifically the CDS market to estimate expected cash flows. These models take into consideration any unique characteristics of the securities and make various adjustments to arrive at an appropriate issuer-specific loss adjusted credit curve. This credit curve is then used with the relevant recovery rates to estimate expected cash flows and modeling of additional features, including illiquidity adjustments, if necessary, to price the security by discounting those loss adjusted cash flows. In cases where a credit curve cannot be developed from the specific security features, the valuation methodology takes into consideration other market observable inputs, including: 1) the most appropriate comparable security(ies) of the issuer; 2) issuer-specific CDS spreads; 3) bonds or CDS spreads of comparable issuers with similar characteristics such as rating, geography, or sector; or 4) bond indices that are comparative in rating, industry, maturity and region. The pricing data and market quotes the Company obtains from outside sources, including third party pricing services, are reviewed internally for reasonableness. If a fair value appears unreasonable, the Company will re-examine the inputs and assess the reasonableness of the pricing data with the vendor. Additionally, the Company may compare the inputs to relevant market indices and other performance measurements. Based on management's analysis, the valuation is confirmed or may be revised if there is evidence of a more appropriate estimate of fair value based on available market data. The Company has performed verification of the inputs and calculations in any valuation models to confirm that the valuations represent reasonable estimates of fair value. The fixed maturity securities classified as Level 3 consist of securities with limited or no observable valuation inputs. For Level 3 securities, the Company estimates the fair value of these securities by obtaining non-binding broker quotes from a limited number of brokers. These brokers base their quotes on a combination of their knowledge of the current pricing environment and market conditions. The Company considers these inputs to be unobservable. The Company also considers a variety of significant valuation inputs in the valuation process, including forward exchange rates, yen swap rates, dollar swap rates, interest rate volatilities, credit spread data on specific issuers, assumed default and default recovery rates, and certain probability assumptions. In obtaining these valuation inputs, the Company has determined that certain pricing assumptions and data used by its pricing sources are difficult to validate or corroborate by the market and/or appear to be internally developed rather than observed in or corroborated by the market. The use of these unobservable valuation inputs causes more subjectivity in the valuation process for these securities. For the periods presented, the Company has not adjusted the quotes or prices it obtains from the pricing services and brokers it uses. The following tables present the pricing sources for the fair values of the Company's fixed maturity and equity securities. March 31, 2018 (In millions) Quoted Prices in Active Markets for Identical Assets Significant Observable Inputs Significant Unobservable Inputs Total Securities available for sale, carried at fair value: Fixed maturity securities: (1) Government and agencies: Third party pricing vendor $ 35,325 $ 1,411 $ 0 $ 36,736 Total government and agencies 35,325 1,411 0 36,736 Municipalities: Third party pricing vendor 0 1,373 0 1,373 Total municipalities 0 1,373 0 1,373 Mortgage- and asset-backed securities: Third party pricing vendor 0 269 0 269 Broker/other 0 0 186 186 Total mortgage- and asset-backed securities 0 269 186 455 Public utilities: Third party pricing vendor 0 7,724 0 7,724 Broker/other 0 0 83 83 Total public utilities 0 7,724 83 7,807 Sovereign and supranational: Third party pricing vendor 0 1,866 0 1,866 Total sovereign and supranational 0 1,866 0 1,866 Banks/financial institutions: Third party pricing vendor 0 9,120 0 9,120 Broker/other 0 0 24 24 Total banks/financial institutions 0 9,120 24 9,144 Other corporate: Third party pricing vendor 0 31,509 0 31,509 Broker/other 0 0 143 143 Total other corporate 0 31,509 143 31,652 Total securities available for sale $ 35,325 $ 53,272 $ 436 $ 89,033 (1) Equity securities, carried at fair value: (1) Third party pricing vendor $ 1,015 $ 77 $ 0 $ 1,092 Broker/other 0 0 16 16 Total equity securities $ 1,015 $ 77 $ 16 $ 1,108 (1) (1) Includes perpetual securities March 31, 2018 (In millions) Quoted Prices in Active Markets for Identical Assets Significant Observable Inputs Significant Unobservable Inputs Total Securities held to maturity, carried at amortized cost: Fixed maturity securities: Government and agencies: Third party pricing vendor $ 28,317 $ 0 $ 0 $ 28,317 Total government and agencies 28,317 0 0 28,317 Municipalities: Third party pricing vendor 0 493 0 493 Total municipalities 0 493 0 493 Mortgage- and asset-backed securities: Third party pricing vendor 0 9 0 9 Broker/other 0 0 19 19 Total mortgage- and asset-backed securities 0 9 19 28 Public utilities: Third party pricing vendor 0 3,891 0 3,891 Total public utilities 0 3,891 0 3,891 Sovereign and supranational: Third party pricing vendor 0 1,919 0 1,919 Total sovereign and supranational 0 1,919 0 1,919 Banks/financial institutions: Third party pricing vendor 0 2,477 0 2,477 Total banks/financial institutions 0 2,477 0 2,477 Other corporate: Third party pricing vendor 0 3,343 0 3,343 Total other corporate 0 3,343 0 3,343 Total securities held to maturity $ 28,317 $ 12,132 $ 19 $ 40,468 December 31, 2017 (In millions) Quoted Prices in Active Markets Significant Observable Significant Unobservable Inputs Total Securities available for sale, carried at fair value: Fixed maturity securities: (1) Government and agencies: Third party pricing vendor $ 30,109 $ 1,121 $ 0 $ 31,230 Total government and agencies 30,109 1,121 0 31,230 Municipalities: Third party pricing vendor 0 1,370 0 1,370 Total municipalities 0 1,370 0 1,370 Mortgage- and asset-backed securities: Third party pricing vendor 0 269 0 269 Broker/other 0 0 175 175 Total mortgage- and asset-backed securities 0 269 175 444 Public utilities: Third party pricing vendor 0 7,886 0 7,886 Broker/other 0 0 68 68 Total public utilities 0 7,886 68 7,954 Sovereign and supranational: Third party pricing vendor 0 1,807 0 1,807 Broker/other 0 102 0 102 Total sovereign and supranational 0 1,909 0 1,909 Banks/financial institutions: Third party pricing vendor 0 8,908 0 8,908 Broker/other 0 0 25 25 Total banks/financial institutions 0 8,908 25 8,933 Other corporate: Third party pricing vendor 0 32,327 0 32,327 Broker/other 0 0 146 146 Total other corporate 0 32,327 146 32,473 Total securities available for sale $ 30,109 $ 53,790 $ 414 $ 84,313 (1) Equity securities, carried at fair value: Third party pricing vendor $ 1,001 $ 6 $ 0 $ 1,007 Broker/other 0 0 16 16 Total equity securities $ 1,001 $ 6 $ 16 $ 1,023 (1) Includes perpetual securities December 31, 2017 (In millions) Quoted Prices in Active Markets Significant Observable Significant Unobservable Inputs Total Securities held to maturity, carried at amortized cost: Fixed maturity securities: Government and agencies: Third party pricing vendor $ 26,491 $ 0 $ 0 $ 26,491 Total government and agencies 26,491 0 0 26,491 Municipalities: Third party pricing vendor 0 462 0 462 Total municipalities 0 462 0 462 Mortgage- and asset-backed securities: Third party pricing vendor 0 8 0 8 Broker/other 0 0 19 19 Total mortgage- and asset-backed securities 0 8 19 27 Public utilities: Third party pricing vendor 0 3,698 0 3,698 Total public utilities 0 3,698 0 3,698 Sovereign and supranational: Third party pricing vendor 0 1,835 0 1,835 Total sovereign and supranational 0 1,835 0 1,835 Banks/financial institutions: Third party pricing vendor 0 2,387 0 2,387 Total banks/financial institutions 0 2,387 0 2,387 Other corporate: Third party pricing vendor 0 3,172 0 3,172 Total other corporate 0 3,172 0 3,172 Total securities held to maturity $ 26,491 $ 11,562 $ 19 $ 38,072 The following is a discussion of the determination of fair value of the Company's remaining financial instruments. Derivatives The Company uses derivative instruments to manage the risk associated with certain assets. However, the derivative instrument may not be classified in the same fair value hierarchy level as the associated asset. Inputs used to value derivatives include, but are not limited to, interest rates, credit spreads, foreign currency forward and spot rates, and interest volatility. The fair values of the foreign currency forwards and options associated with certain investments; the foreign currency forwards and options used to hedge foreign exchange risk from the Company's net investment in Aflac Japan and economically hedge certain portions of forecasted cash flows denominated in yen; and the foreign currency swaps associated with certain senior notes and subordinated debentures are based on the amounts the Company would expect to receive or pay. The determination of the fair value of these derivatives is based on observable market inputs, therefore they are classified as Level 2. For derivatives associated with VIEs where the Company is the primary beneficiary, the Company is not the direct counterparty to the swap contracts. As a result, the fair value measurements incorporate the credit risk of the collateral associated with the VIE. The Company receives valuations from a third party pricing vendor for these derivatives. Based on an analysis of these derivatives and a review of the methodology employed by the pricing vendor, the Company determined that due to the long duration of these swaps and the need to extrapolate from short-term observable data to derive and measure long-term inputs, certain inputs, assumptions and judgments are required to value future cash flows that cannot be corroborated by current inputs or current observable market data. As a result, the derivatives associated with the Company's consolidated VIEs are classified as Level 3 of the fair value hierarchy. Other investments Other investments where fair value is disclosed above include short-term investments and loan receivables. Loan receivables include transitional real estate loans, commercial mortgage loans and middle market loans. The Company's loan receivables do not have readily determinable market prices and generally lack market liquidity. Fair values for loan receivables are determined based on the present value of expected future cash flows discounted at the applicable U.S. Treasury or London Interbank Offered Rate (LIBOR) yield plus an appropriate spread that considers other risk factors, such as credit and liquidity risk. These spreads are provided by the applicable asset managers based on their knowledge of the current loan pricing environment and market conditions. The spreads are a significant component of the pricing inputs and are generally considered unobservable. Therefore, these investments have been assigned a Level 3 within the fair value hierarchy. Other policyholders' funds The largest component of the other policyholders' funds liability is the Company's annuity line of business in Aflac Japan. The Company's annuities have fixed benefits and premiums. For this product, the Company estimates the fair value to be equal to the cash surrender value. This is analogous to the value paid to policyholders on the valuation date if they were to surrender their policy. The Company periodically checks the cash value against discounted cash flow projections for reasonableness. The Company considers its inputs for this valuation to be unobservable and have accordingly classified this valuation as Level 3. Notes payable The fair values of the Company's publicly issued notes payable are determined by utilizing available sources of observable inputs from third party pricing vendors and are classified as Level 2. The fair values of the Company's yen-denominated loans approximate their carrying values and are classified as Level 3. Transfers between Hierarchy Levels and Level 3 Rollforward During the three -month periods ended March 31, 2018 and 2017 , respectively, there were no transfers between Level 1 and 2 for assets and liabilities that are measured and carried at fair value on a recurring basis. The following tables present the changes in fair value of the Company's investments and derivatives carried at fair value classified as Level 3. Three Months Ended Fixed Maturity Securities Equity Derivatives (1) (In millions) Mortgage- Public Banks/ Other Foreign Credit Total Balance, beginning of period $ 175 $ 68 $ 25 $ 146 $ 16 $ 22 $ 1 $ 453 Realized investment gains (losses) included 0 0 0 0 0 126 0 126 Unrealized gains (losses) included in other 11 (1 ) (1 ) (2 ) 0 6 0 13 Purchases, issuances, sales and settlements: Purchases 0 16 0 0 0 0 0 16 Issuances 0 0 0 0 0 0 0 0 Sales 0 0 0 0 0 0 0 0 Settlements 0 0 0 (1 ) 0 0 0 (1 ) Transfers into Level 3 0 0 0 0 0 0 0 0 Transfers out of Level 3 0 0 0 0 0 0 0 0 Balance, end of period $ 186 $ 83 $ 24 $ 143 $ 16 $ 154 $ 1 $ 607 Changes in unrealized gains (losses) relating $ 0 $ 0 $ 0 $ 0 $ 0 $ 126 $ 0 $ 126 (1) Derivative assets and liabilities are presented net Three Months Ended Fixed Maturity Securities Equity Derivatives (1) (In millions) Mortgage- Public Banks/ Other Foreign Credit Total Balance, beginning of period $ 198 $ 16 $ 25 $ 0 $ 3 $ (21 ) $ 2 $ 223 Realized investment gains (losses) included in earnings 0 0 0 0 0 38 0 38 Unrealized gains (losses) included in other comprehensive income (loss) 6 0 (1 ) 0 0 2 0 7 Purchases, issuances, sales and settlements: Purchases 0 0 0 35 2 0 0 37 Issuances 0 0 0 0 0 0 0 0 Sales 0 0 0 0 (1 ) 0 0 (1 ) Settlements (9 ) 0 0 0 0 0 0 (9 ) Transfers into Level 3 0 0 0 0 0 0 0 0 Transfers out of Level 3 0 0 0 0 0 0 0 0 Balance, end of period $ 195 $ 16 $ 24 $ 35 $ 4 $ 19 $ 2 $ 295 Changes in unrealized gains (losses) relating $ 0 $ 0 $ 0 $ 0 $ 0 $ 38 $ 0 $ 38 (1) Derivative assets and liabilities are presented net Fair Value Sensitivity Level 3 Significant Unobservable Input Sensitivity The following tables summarize the significant unobservable inputs used in the valuation of the Company's Level 3 investments and derivatives carried at fair value. Included in the tables are the inputs or range of possible inputs that have an effect on the overall valuation of the financial instruments. March 31, 2018 (In millions) Fair Value Valuation Technique(s) Unobservable Input Range Assets: Securities available for sale, carried at fair value: Fixed maturity securities: Mortgage- and asset-backed securities $ 186 Consensus pricing Offered quotes N/A (c) Public utilities 83 Discounted cash flow Credit spreads N/A (c) Banks/financial institutions 24 Consensus pricing Offered quotes N/A (c) Other corporate 143 Discounted cash flow Credit spreads N/A (c) Equity securities 16 Net asset value Offered quotes N/A (c) Other assets: Foreign currency swaps 185 Discounted cash flow Interest rates (USD) 2.78% - 2.82% (a) Interest rates (JPY) .26% - .85% (b) CDS spreads 13 - 101 bps 55 Discounted cash flow Interest rates (USD) 2.78% - 2.82% (a) Interest rates (JPY) .26% - .85% (b) Credit default swaps 1 Discounted cash flow Base correlation 49.98% - 54.13% (d) CDS spreads 15 bps Recovery rate 37.24% Total assets $ 693 (a) Inputs derived from U.S. long-term rates to accommodate long maturity nature of the Company's swaps (b) Inputs derived from Japan long-term rates to accommodate long maturity nature of the Company's swaps (c) N/A represents securities where the Company receives unadjusted broker quotes and for which there is no transparency into the providers' valuation techniques or unobservable inputs. (d) Range of base correlation for the Company's bespoke tranche for attachment and detachment points corresponding to market indices March 31, 2018 (In millions) Fair Value Valuation Technique(s) Unobservable Input Range Liabilities: Other liabilities: Foreign currency swaps $ 84 Discounted cash flow Interest rates (USD) 2.78% - 2.82% (a) Interest rates (JPY) .26% - .85% (b) CDS spreads 17 - 170 bps 2 Discounted cash flow Interest rates (USD) 2.78% - 2.82% (a) Interest rates (JPY) .26% - .85% (b) Total liabilities $ 86 (a) Inputs derived from U.S. long-term rates to accommodate long maturity nature of the Company's swaps (b) Inputs derived from Japan long-term rates to accommodate long maturity nature of the Company's swaps December 31, 2017 (In millions) Fair Value Valuation Technique(s) Unobservable Input Range Assets: Securities available for sale, carried at fair value: Fixed maturity securities: Mortgage- and asset-backed securities $ 175 Consensus pricing Offered quotes N/A (c) Public utilities 68 Discounted cash flow Credit spreads N/A (c) Banks/financial institutions 25 Consensus pricing Offered quotes N/A (c) Other corporate 146 Discounted cash flow Credit spreads N/A (c) Equity securities 16 Net asset value Offered quotes N/A (c) Other assets: Foreign currency swaps 80 Discounted cash flow Interest rates (USD) 2.40% - 2.54% (a) Interest rates (JPY) .26% - .85% (b) CDS spreads 9 - 90 bps 70 Discounted cash flow Interest rates (USD) 2.40% - 2.54% (a) Interest rates (JPY) .26% - .85% (b) Credit default swaps 1 Discounted cash flow Base correlation 46.33% - 49.65% (d) CDS spreads 25 bps Recovery rate 37.24% Total assets $ 581 (a) Inputs derived from U.S. long-term rates to accommodate long maturity nature of the Company's swaps (b) Inputs derived from Japan long-term rates to accommodate long maturity nature of the Company's swaps (c) N/A represents securities where the Company receives unadjusted broker quotes and for which there is no transparency into the providers' valuation techniques or unobservable inputs. (d) Range of base correlation for the Company's bespoke tranche for attachment and detachment points corresponding to market indices December 31, 2017 (In millions) Fair Value Valuation Technique(s) Unobservable Input Range Liabilities: Other liabilities: Foreign currency swaps $ 120 Discounted cash flow Interest rates (USD) 2.40% - 2.54% (a) Interest rates (JPY) .26% - .85% (b) CDS spreads 13 - 157 bps 8 Discounted cash flow Interest rates (USD) 2.40% - 2.54% (a) Interest rates (JPY) .26% - .85% (b) Total liabilities $ 128 (a) Inputs derived from U.S. long-term rates to accommodate long maturity nature of the Company's swaps (b) Inputs derived from Japan long-term rates to accommodate long maturity nature of the Company's swaps The following is a discussion of the significant unobservable inputs or valuation techniques used in determining the fair value of securities and derivatives classified as Level 3. Net Asset Value The Company holds certain unlisted equity securities whose fair value is derived based on the financial statements published by the investee. These securities do not trade on an active market and the valuations derived are dependent on the availability of timely financial reporting of the investee. Net asset value is an unobservable input in the determination of fair value of equity securities. Offered Quotes In circumstances where the Company's valuation model price is overridden because it implies a value that is not consistent with current market conditions, the Company will solicit bids from a limited number of brokers. The Company also receives unadjusted prices from brokers for its mortgage and asset-backed securities. These quotes are non-binding but are reflective of valuation best estimates at that particular point in time. Offered quotes are an unobservable input in the determination of fair value of mortgage- and asset-backed securities, certain banks/financial institutions, certain other corporate, and equity securities investments. Interest Rates, CDS Spreads, Foreign Exchange Rates The significant drivers of the valuation of the interest and foreign exchange swaps are interest rates, foreign exchange rates and CDS spreads. The Company's swaps have long maturities that increase the sensitivity of the swaps to interest rate fluctuations. Since most of the Company's yen-denominated cross currency swaps are in a net liability position, an increase in interest rates will decrease the liabilities and increase the value of the swap. Foreign exchange swaps also have a lump-sum final settlement of foreign exchange principal receivables at the termination of the swap. An increase in yen interest rates will decrease the value of the final settlement foreign exchange receivables and decrease the value of the swap, and an increase in U.S. dollar interest rates will increase the swap value. A similar sensitivity pattern is observed for the foreign exchange rates. When the spot U.S. dollar/Japanese yen (USD/JPY) foreign exchange rate decreases and the swap is receiving a final exchange payment in JPY, the swap value will increase due to the appreciation of the JPY. Most of the Company's swaps are designed to receive payments in JPY at the termination and will thus be impacted by the USD/JPY foreign exchange rate in this way. In cases where there is no final foreign exchange receivable in JPY and the Company is paying JPY as interest payments and receiving USD, a decrease in the foreign exchange rate will lead to a decrease in the swap value. The extinguisher feature in most of the Company's VIE swaps results in a cessation of cash flows and no further payments between the parties to the swap in the event of a default on the referenced or underlying collateral. To price this feature, the Company applies the survival probability of the referenced entity to the projected cash flows. The survival probability uses the CDS spreads and recovery rates to adjust the present value of the cash flows. For extinguisher swaps with positive values, an increase in CDS spreads decreases the likelihood of receiving the final exchange payments and reduces the value of the swap. Base Correlations, CDS Spreads, Recovery Rates The Company's remaining collateralized debt obligation (CDO) is a tranche on a basket of single-name credit default swaps. The risk in this synthetic CDO comes from the single-name CDS risk and the correlations between the single names. The valuation of synthetic CDOs is dependent on the calibration of market prices for interest rates, single name CDS default probabilities and base correlation using financial modeling tools. Since there is limited or no observable data available for this tranche, the base correlations must be obtained from commonly traded market tranches such as the CDX and iTraxx indices. From the historical prices of these indices, base correlations can be obtained to develop a pricing curve of CDOs with different seniorities. Since the reference entities of the market indices do not match those in the portfolio underlying the synthetic CDO to be valued, several processing steps are taken to map the CDO in the Company's portfolio to the indices. With the base correlation determined and the appropriate spreads selected, a valuation is calculated. An increase in the CDS spreads in the underlying portfolio leads to a decrease in the value due to higher probability of defaults and losses. The impact on the valuation due to base correlation depends on a number of factors, including the riskiness between market tranches and the modeled tranche based on the Company's portfolio and the equivalence between detachment points in these tranches. Generally speaking, an increase in base correlation will decrease the value of the senior tranches while increasing the value of junior tranches. This may result in a positive or negative value change. The CDO tranche in the Company's portfolio is a senior mezzanine tranche and, due to the low level of credit support for this type of tranche, exhibits equity-like behavior. As a result, an increase in recovery rates tends to cause its value to decrease. Base correlations, CDS spreads, and recovery rates are unobservable inputs in the determination of fair value of credit default swaps. For additional information on the Company's investments and financial instruments, see the accompanying Notes 1, 3 and 4 and Notes 1, 3 and 4 of the Notes to the Consolidated Financial Statements in the 2017 Annual Report.

POLICY LIABILITIES

POLICY LIABILITIES	3 Months Ended
	Mar. 31, 2018
Insurance Loss Reserves [Abstract]
POLICY LIABILITIES	POLICY LIABILITIES Changes in the liability for unpaid policy claims were as follows: Three Months Ended (In millions) 2018 2017 Unpaid supplemental health claims, beginning of period $ 3,884 $ 3,707 Less reinsurance recoverables 30 27 Net balance, beginning of period 3,854 3,680 Add claims incurred during the period related to: Current year 1,842 1,737 Prior years (192 ) (111 ) Total incurred 1,650 1,626 Less claims paid during the period on claims incurred during: Current year 518 505 Prior years 1,116 1,055 Total paid 1,634 1,560 Effect of foreign exchange rate changes on unpaid claims 142 80 Net balance, end of period 4,012 3,826 Add reinsurance recoverables 31 29 Unpaid supplemental health claims, end of period 4,043 3,855 Unpaid life claims, end of period 587 375 Total liability for unpaid policy claims $ 4,630 $ 4,230 The incurred claims development related to prior years reflects favorable claims experience compared to previous estimates. The favorable claims development of $192 million for the three -month period ended March 31, 2018 comprises approximately $97 million from Japan, which represents approximately 51% of the total. Excluding the impact of foreign exchange of a loss of approximately $5 million from December 31, 2017 to March 31, 2018 , the favorable claims development in Japan would have been approximately $92 million , representing approximately 48% of the total. The Company has experienced continued favorable claim trends in 2018 for its core health products in Japan. The Company's experience in Japan related to the average length of stay in the hospital for cancer treatment has shown continued decline in the current period. In addition, cancer treatment patterns in Japan are continuing to be influenced by significant advances in early-detection techniques and by the increased use of pathological diagnosis rather than clinical exams. Additionally, follow-up radiation and chemotherapy treatments are occurring more often on an outpatient basis. Such changes in treatment not only increase the quality of life and initial outcomes for the patients, but also decrease the average length of each hospital stay, resulting in favorable claims development. The remainder of the favorable claims development related to prior years for the three -month period ended March 31, 2018 , reflects Aflac U.S. favorable claims experience compared to previous estimates, primarily in the cancer and accident lines of business.

REINSURANCE

REINSURANCE	3 Months Ended
	Mar. 31, 2018
Reinsurance Disclosures [Abstract]
REINSURANCE	REINSURANCE The Company periodically enters into fixed quota-share coinsurance agreements with other companies in the normal course of business. For each of its reinsurance agreements, the Company determines whether the agreement provides indemnification against loss or liability relating to insurance risk in accordance with applicable accounting standards. Reinsurance premiums and benefits paid or provided are accounted for on bases consistent with those used in accounting for the original policies issued and the terms of the reinsurance contracts. Premiums and benefits are reported net of insurance ceded. The Company has recorded a deferred profit liability related to reinsurance transactions. The remaining deferred profit liability of $1.0 billion , as of March 31, 2018 , is included in future policy benefits in the consolidated balance sheet and is being amortized into income over the expected lives of the policies. The Company has also recorded a reinsurance recoverable for reinsurance transactions, which is included in other assets in the consolidated balance sheet and had a remaining balance of $969 million and $908 million as of March 31, 2018 , and December 31, 2017 , respectively. The increase in the reinsurance recoverable balance was driven by two aggregating factors: yen strengthening and the growth in reserves related to the business that has been reinsured as the policies age. The spot yen/dollar exchange rate strengthened by approximately 6.4% and ceded reserves increased approximately .4% from December 31, 2017 , to March 31, 2018 . The following table reconciles direct premium income and direct benefits and claims to net amounts after the effect of reinsurance. Three Months Ended (In millions) 2018 2017 Direct premium income $ 4,833 $ 4,724 Ceded to other companies: Ceded Aflac Japan closed blocks (129 ) (130 ) Other (15 ) (12 ) Assumed from other companies: Retrocession activities 54 54 Other 2 2 Net premium income $ 4,745 $ 4,638 Direct benefits and claims $ 3,119 $ 3,129 Ceded benefits and change in reserves for future benefits: Ceded Aflac Japan closed blocks (117 ) (122 ) Eliminations 12 13 Other (12 ) (11 ) Assumed from other companies: Retrocession activities 52 54 Eliminations (12 ) (13 ) Other 0 2 Benefits and claims, net $ 3,042 $ 3,052 These reinsurance transactions are indemnity reinsurance that do not relieve the Company from its obligations to policyholders. In the event that the reinsurer is unable to meet their obligations, the Company remains liable for the reinsured claims. As a part of its capital contingency plan, the Company entered into a committed reinsurance facility agreement on December 1, 2015 in the amount of approximately 110 billion yen. This reinsurance facility agreement was renewed in 2017 and is effective until December 31, 2018. There are also additional commitment periods of a one-year duration each which are automatically extended unless notification is received from the reinsurer within 60 days prior to the expiration. The reinsurer can withdraw from the committed facility if Aflac‘s Standard and Poor's (S&P) rating drops below BBB-. As of March 31, 2018 , the Company has not executed a reinsurance treaty under this committed reinsurance facility.

NOTES PAYABLE

NOTES PAYABLE	3 Months Ended
	Mar. 31, 2018
Debt Disclosure [Abstract]
NOTES PAYABLE	NOTES PAYABLE A summary of notes payable follows: (In millions) March 31, 2018 December 31, 2017 2.40% senior notes due March 2020 $ 548 $ 548 4.00% senior notes due February 2022 348 348 3.625% senior notes due June 2023 697 697 3.625% senior notes due November 2024 746 745 3.25% senior notes due March 2025 446 446 2.875% senior notes due October 2026 297 297 6.90% senior notes due December 2039 220 220 6.45% senior notes due August 2040 254 254 4.00% senior notes due October 2046 394 394 Yen-denominated senior notes and subordinated debentures: .932% senior notes due January 2027 (principal amount 60.0 billion yen) 562 528 2.108% subordinated debentures due October 2047 (principal amount 60.0 billion yen) 559 526 Yen-denominated loans: Variable interest rate loan due September 2021 (.32% in 2018 and 2017, principal amount 5.0 billion yen) 47 44 Variable interest rate loan due September 2023 (.47% in 2018 and 2017, principal amount 25.0 billion yen) 234 220 Capitalized lease obligations payable through 2025 20 22 Total notes payable $ 5,372 $ 5,289 Amounts in the table above are reported net of debt issuance costs and issuance premiums or discounts, if applicable, that are being amortized over the life of the notes. A summary of the Company's lines of credit as of March 31, 2018 follows: Borrower Type Original Term Expiration Date Capacity Amount Outstanding Interest Rate on Borrowed Amount Maturity Period Commitment Fee Business Purpose Aflac Incorporated uncommitted bilateral 364 days November 30, 2018 $100 million $0 million The rate quoted by the bank and agreed upon at the time of borrowing Up to 3 months None General corporate purposes Aflac Incorporated unsecured revolving 3 years March 31, 2019, or the date commitments are terminated pursuant to an event of default 100.0 billion yen 0.0 billion yen A rate per annum equal to (a) Tokyo interbank market rate (TIBOR) plus, the alternative applicable TIBOR margin during the availability period from the closing date to the commitment termination date or (b) the TIBOR rate offered by the agent to major banks in yen for the applicable period plus, the applicable alternative TIBOR margin during the term out period No later than .30% to .50%, depending on the Parent Company's debt ratings as of the date of determination General corporate purposes, including a capital contingency plan for the operations of the Parent Company Aflac Incorporated unsecured revolving 5 years September 18, 2020, or the date commitments are terminated pursuant to an event of default (1) 55.0 billion yen, or the equivalent amount in U.S. dollars 0.0 billion yen A rate per annum equal to, at the Company's option, either, (a) London Interbank Offered Rate (LIBOR) adjusted for certain costs or (b) a base rate determined by reference to the highest of (1) the federal funds rate plus 1/2 of 1%, (2) the rate of interest for such day announced by Mizuho Bank, Ltd. as its prime rate, or (3) the eurocurrency rate for an interest period of one month plus 1.00%, in each case plus an applicable margin No later than September 18, 2020 (1) .085% to .225%, depending on the Parent Company's debt ratings as of the date of determination General corporate purposes, including a capital contingency plan for the operations of the Parent Company Aflac Incorporated uncommitted bilateral None specified None specified $50 million $0 million A rate per annum equal to, at the Parent Company's option, either (a) a eurocurrency rate determined by reference to the agent's LIBOR for the interest period relevant to such borrowing or (b) the base rate determined by reference to the greater of (i) the prime rate as determined by the agent, and (ii) the sum of 0.50% and the federal funds rate for such day Up to 3 months None General corporate purposes Aflac (2) uncommitted revolving 364 days November 30, 2018 $250 million $0 million USD three-month LIBOR plus 75 basis points per annum 3 months None General corporate purposes Aflac Incorporated (2) uncommitted revolving 364 days April 2, 2018 37.5 billion yen 0.0 billion yen Three-month TIBOR plus 80 basis points per annum 3 months None General corporate purposes (1) Expiration and maturity period dates were updated in April 2018 to April 4, 2023 (2) Intercompany credit agreement The Company was in compliance with all of the covenants of its notes payable and lines of credit at March 31, 2018. No events of default or defaults occurred during the three-month period ended March 31, 2018. For additional information, see Notes 4 and 9 of the Notes to the Consolidated Financial Statements in the 2017 Annual Report.

INCOME TAXES

INCOME TAXES	3 Months Ended
	Mar. 31, 2018
Income Tax Disclosure [Abstract]
Income Tax Disclosure [Text Block]	9. INCOME TAXES For the United States, the Tax Cuts and Jobs Act (Tax Act) was signed into law on December 22, 2017. Effective January 1, 2018, the Tax Act imposes a broad number of changes in tax law, including the permanent reduction of the U.S. federal statutory corporate income tax rate from 35% to 21% . The Company expects to complete its accounting for the effects of the Tax Act over the measurement period of up to one year from the enactment date, as permitted by SEC Staff Accounting Bulletin No. 118 (SAB 118). As of the enactment date, the Company estimated provisional amounts for its deferred taxes, including related valuation allowance, resulting in a reduction of its deferred tax assets (DTAs) by approximately $1.0 billion and its deferred tax liabilities (DTLs) by $2.9 billion , for a net DTL reduction of approximately $1.9 billion . The Company believes that these amounts represent reasonable estimates in accordance with SAB 118. The provisions of ASC 740-10, Income Taxes , require that the effects of changes in tax law on deferred taxes be recognized as a component of the income tax provision in the period the tax rate change was enacted. Therefore, the $1.9 billion provisional amount of net DTL reduction was recorded in the fourth quarter of 2017 as a reduction in the “Income tax expense, Deferred” line item of the Company’s consolidated statement of earnings. As of the first quarter of 2018, the Company has no update to this estimated benefit. The following includes an overview of the existing current and deferred balances for which calculation of income tax effects of the Tax Act has not been completed: Japan deferred tax balances: The Tax Act reduces the U.S. tax rate to 21% , effective January 1, 2018. Prior to the reduction in rate, the Japan deferred tax balances were completely offset by an anticipatory foreign tax credit. As a result of the rate reduction, the Japan deferred tax balance will no longer be offset by an anticipatory foreign tax credit as all of the foreign tax credits will be used to offset the U.S. deferred tax balance of the Aflac Japan branch. The Company has not yet completed its analysis of the components of the Japan tax computation, including a complete validation of the Aflac Japan tax basis. Additional time is needed to collect, analyze, and validate the detailed data underlying the deferred tax amounts in the Aflac Japan branch. As of the fourth quarter of 2017, the Company had recorded a provisional amount of $4.5 billion of net DTL related to this item. Valuation allowances: The Company must assess whether its valuation allowance analyses are impacted by various aspects of the Tax Act with a primary focus on any unused anticipatory foreign tax credits. As the Company has recorded provisional amounts related to the Japan deferred tax balances, any corresponding determination of the need for or change in a valuation allowance is also provisional. As of the fourth quarter of 2017, the Company had recorded a provisional valuation allowance of $.7 billion against its anticipatory foreign tax credit asset. The impact of the Tax Act may differ, possibly materially, from the recorded provisional amounts.

SHAREHOLDERS' EQUITY

SHAREHOLDERS' EQUITY	3 Months Ended
	Mar. 31, 2018
Stockholders' Equity Note [Abstract]
SHAREHOLDERS' EQUITY	SHAREHOLDERS’ EQUITY See Note 1 for a discussion of the stock split that occurred in March 2018. All share and per-share amounts have been adjusted to reflect the stock split for any of the periods presented. The following table is a reconciliation of the number of shares of the Company's common stock for the three -month periods ended March 31 . (In thousands of shares) 2018 2017 Common stock - issued: Balance, beginning of period 1,345,762 1,342,498 Exercise of stock options and issuance of restricted shares 1,014 868 Balance, end of period 1,346,776 1,343,366 Treasury stock: Balance, beginning of period 564,852 530,877 Purchases of treasury stock: Open market 6,640 16,986 Other 315 288 Dispositions of treasury stock: Shares issued to AFL Stock Plan (384 ) (494 ) Exercise of stock options (305 ) (256 ) Other (99 ) (40 ) Balance, end of period 571,019 547,361 Shares outstanding, end of period 775,757 796,005 Outstanding share-based awards are excluded from the calculation of weighted-average shares used in the computation of basic earnings per share (EPS). The following table presents the approximate number of share-based awards to purchase shares, on a weighted-average basis, that were considered to be anti-dilutive and were excluded from the calculation of diluted earnings per share for the following periods. Three Months Ended (In thousands) 2018 2017 Anti-dilutive share-based awards 9 642 Share Repurchase Program During the first three months of 2018 , the Company repurchased 6.6 million shares of its common stock in the open market for $296 million as part of its share repurchase program. During the first three months of 2017 , the Company repurchased 17.0 million shares of its common stock in the open market for $600 million as part of its share repurchase program. In August 2017, the Company's board of directors authorized the purchase of an additional 80 million shares of its common stock. As of March 31, 2018 , a remaining balance of 91.4 million shares of the Company's common stock was available for purchase under share repurchase authorizations by its board of directors. Reclassifications from Accumulated Other Comprehensive Income The tables below are reconciliations of accumulated other comprehensive income by component for the following periods. Changes in Accumulated Other Comprehensive Income Three Months Ended (In millions) Unrealized Foreign Unrealized Unrealized Pension Total Balance, beginning of period $ (1,750 ) $ 5,964 $ (23 ) $ (163 ) $ 4,028 Other comprehensive 447 (983 ) 2 (37 ) (571 ) Amounts reclassified from 0 225 (1) 0 3 228 Net current-period other 447 (758 ) 2 (34 ) (343 ) Balance, end of period $ (1,303 ) $ 5,206 $ (21 ) $ (197 ) $ 3,685 (1) Includes amounts reclassified due to changes in accounting principles of $(148) related to financial instruments and $374 related to tax effects from tax reform All amounts in the table above are net of tax. Three Months Ended (In millions) Unrealized Foreign Unrealized Unrealized Pension Liability Adjustment Total Balance, beginning of period $ (1,983 ) $ 4,805 $ (24 ) $ (168 ) $ 2,630 Other comprehensive 333 (341 ) 2 (4 ) (10 ) Amounts reclassified from 0 10 0 2 12 Net current-period other 333 (331 ) 2 (2 ) 2 Balance, end of period $ (1,650 ) $ 4,474 $ (22 ) $ (170 ) $ 2,632 All amounts in the table above are net of tax. For the three-month period ended March 31, 2018, see Note 1 for discussion of the amounts reclassified between AOCI and retained earnings upon the adoption of new accounting pronouncements. The tables below summarize the amounts reclassified from each component of accumulated other comprehensive income into net earnings for the following periods. Reclassifications Out of Accumulated Other Comprehensive Income (In millions) Three Months Ended Details about Accumulated Other Comprehensive Income Components Amount Reclassified from Accumulated Other Comprehensive Income Affected Line Item in the Unrealized gains (losses) on available-for-sale $ 2 Sales and redemptions 0 Other-than-temporary impairment 2 Total before tax (1 ) Tax (expense) or benefit (1) $ 1 Net of tax Amortization of defined benefit pension items: Actuarial gains (losses) $ (4 ) Acquisition and operating expenses (2) Prior service (cost) credit 0 Acquisition and operating expenses (2) 1 Tax (expense) or benefit (1) $ (3 ) Net of tax Total reclassifications for the period $ (2 ) Net of tax (1) Based on 27% blended tax rate (2) These accumulated other comprehensive income components are included in the computation of net periodic pension cost (see Note 12 for additional details). (In millions) Three Months Ended Details about Accumulated Other Comprehensive Income Components Amount Reclassified from Accumulated Other Comprehensive Income Affected Line Item in the Unrealized gains (losses) on available-for-sale $ (6 ) Sales and redemptions (10 ) Other-than-temporary impairment (16 ) Total before tax 6 Tax (expense) or benefit (1) $ (10 ) Net of tax Amortization of defined benefit pension items: Actuarial gains (losses) $ (3 ) Acquisition and operating expenses (2) Prior service (cost) credit 0 Acquisition and operating expenses (2) 1 Tax (expense) or benefit (1) $ (2 ) Net of tax Total reclassifications for the period $ (12 ) Net of tax (1) Based on 35% tax rate (2) These accumulated other comprehensive income components are included in the computation of net periodic pension cost (see Note 12 for additional details)

SHARE-BASED COMPENSATION

SHARE-BASED COMPENSATION	3 Months Ended
	Mar. 31, 2018
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
SHARE-BASED COMPENSATION	SHARE-BASED COMPENSATION See Note 1 for a discussion of the stock split that occurred in March 2018. All share and per-share amounts have been adjusted to reflect the stock split for any of the periods presented. As of March 31, 2018 , the Company has outstanding share-based awards under the Aflac Incorporated Long-Term Incentive Plan (the “Plan”). Share-based awards are designed to reward employees for their long-term contributions to the Company and provide incentives for them to remain with the Company. The number and frequency of share-based awards are based on competitive practices, operating results of the Company, government regulations, and other factors. The Plan, as amended on February 14, 2017, allows for a maximum number of shares issuable over its term of 75 million shares including 38 million shares that may be awarded in respect of awards other than options or stock appreciation rights. If any awards granted under the Plan are forfeited or are terminated before being exercised or settled for any reason other than tax forfeiture, then the shares underlying the awards will again be available under the Plan. The Plan allows awards to Company employees for incentive stock options (ISOs), non-qualifying stock options (NQSOs), restricted stock, restricted stock units, and stock appreciation rights. Non-employee directors are eligible for grants of NQSOs, restricted stock, and stock appreciation rights. As of March 31, 2018 , approximately 40.5 million shares were available for future grants under this plan. The ISOs and NQSOs have a term of 10 years, and the share-based awards generally vest upon time-based conditions or time and performance-based conditions. Time-based vesting generally occurs after three years. Performance-based vesting conditions generally include the attainment of goals related to Company financial performance. As of March 31, 2018 , the only performance-based awards issued and outstanding were restricted stock awards. Stock options and stock appreciation rights granted under the amended Plan have an exercise price of at least the fair market value of the underlying stock on the grant date and have an expiration date no later than 10 years from the grant date. Time-based restricted stock awards, restricted stock units and stock options granted after January 1, 2017 generally vest on a ratable basis over three years, and awards granted prior to the amendment vest on a three -year cliff basis. The Compensation Committee of the Board of Directors has the discretion to determine vesting schedules . Share-based awards granted to U.S.-based grantees are settled with authorized but unissued Company stock, while those issued to Japan-based grantees are settled with treasury shares. The following table provides information on stock options outstanding and exercisable at March 31, 2018 . Stock Weighted-Average Aggregate Weighted-Average Outstanding 6,306 5.5 $ 99 $ 28.03 Exercisable 4,439 4.4 77 26.45 The Company received cash from the exercise of stock options in the amount of $23 million during the first three months of 2018, compared with $17 million in the first three months of 2017. The tax benefit realized as a result of stock option exercises and restricted stock releases was $12 million in the first three months of 2018, compared with $14 million in the first three months of 2017. As of March 31, 2018 , total compensation cost not yet recognized in the Company's financial statements related to restricted stock awards was $62 million , of which $30 million ( 826 thousand shares) was related to restricted stock awards with a performance-based vesting condition. The Company expects to recognize these amounts over a weighted-average period of approximately 1.5 years. There are no other contractual terms covering restricted stock awards once vested. The following table summarizes restricted stock activity during the three -month period ended March 31 . (In thousands of shares) Shares Weighted-Average Grant-Date Fair Value Per Share Restricted stock at December 31, 2017 3,635 $ 32.40 Granted in 2018 918 44.12 Canceled in 2018 (56 ) 33.18 Vested in 2018 (980 ) 31.50 Restricted stock at March 31, 2018 3,517 $ 35.70 In February 2018, the Company granted 432 thousand performance-based stock awards, which are contingent on the achievement of the Company's financial performance metrics and its market-based conditions. On the date of grant, the Company estimated the fair value of restricted stock awards with market-based conditions using a Monte Carlo simulation model. The model discounts the value of the stock at the assumed vesting date based on the risk-free interest rate. Based on estimates of actual performance versus the vesting thresholds, the calculated fair value percentage pay-out estimate will be updated each quarter. The Company uses third-party analyses to assist in developing the assumptions used in, as well as calibrating, a Monte Carlo simulation model. The Company is responsible for determining the assumptions used in estimating the fair value of its share-based payment awards. For additional information on the Company's long-term share-based compensation plans and the types of share-based awards, see Note 12 of the Notes to the Consolidated Financial Statements included in the 2017 Annual Report.

BENEFIT PLANS

BENEFIT PLANS	3 Months Ended
	Mar. 31, 2018
Defined Benefit Plans and Other Postretirement Benefit Plans Disclosures [Abstract]
BENEFIT PLANS	BENEFIT PLANS The Company has funded defined benefit plans in Japan and the United States, however the U.S. plan was frozen to new participants effective October 1, 2013. The Company also maintains non-qualified, unfunded supplemental retirement plans that provide defined pension benefits in excess of limits imposed by federal tax law for certain Japanese, U.S. and former employees, however the U.S. plan was frozen to new participants effective January 1, 2015. U.S. employees who are not participants in the defined benefit plan receive a nonelective 401(k) employer contribution. The Company provides certain health care benefits for eligible U.S. retired employees, their beneficiaries and covered dependents ("other postretirement benefits"). The health care plan is contributory and unfunded. Effective January 1, 2014, employees eligible for benefits included the following: (1) active employees whose age plus service, in years, equaled or exceeded 80 (rule of 80 ); (2) active employees who were age 55 or older and have met the 15 years of service requirement; (3) active employees who would meet the rule of 80 in the next five years ; (4) active employees who were age 55 or older and who would meet the 15 years of service requirement within the next five years ; and (5) current retirees. For certain employees and former employees, additional coverage is provided for all medical expenses for life. Pension and other postretirement benefit expenses are included in acquisition and operating expenses in the consolidated statement of earnings, which includes $5 million of other components of net periodic pension cost and postretirement costs (other than service costs) for the three months ended March 31, 2018 and 2017, respectively. Total net periodic cost includes the following components: Three Months Ended March 31, Pension Benefits Other Japan U.S. Postretirement Benefits (In millions) 2018 2017 2018 2017 2018 2017 Components of net periodic Service cost $ 5 $ 5 $ 7 $ 6 $ 0 $ 0 Interest cost 2 1 9 8 0 0 Expected return on plan (2 ) (1 ) (7 ) (6 ) 0 0 Amortization of net actuarial 0 0 4 3 0 0 Amortization of prior service 0 0 0 0 0 0 Net periodic (benefit) cost $ 5 $ 5 $ 13 $ 11 $ 0 $ 0 During the three months ended March 31, 2018 , Aflac Japan contributed approximately $6 million (using the weighted-average yen/dollar exchange rate for the three -month period ending March 31, 2018 ) to the Japanese funded defined benefit plan, and Aflac U.S. contributed $10 million to the U.S. funded defined benefit plan. As a result of U.S. tax reform legislation enacted in December 2017, the Company announced it would make a one-time contribution of $500 to the U.S. 401(k) plan to all employees active on December 31, 2017. This contribution was made by January 31, 2018. The Company also announced that it would increase its matching contributions to 100% of each employee's contributions which were not in excess of 4% of the employee's annual cash compensation. This increase became effective on January 1, 2018. For additional information regarding the Company's Japanese and U.S. benefit plans, see Note 14 of the Notes to the Consolidated Financial Statements in the 2017 Annual Report.

COMMITMENTS AND CONTINGENT LIAB

COMMITMENTS AND CONTINGENT LIABILITIES	3 Months Ended
	Mar. 31, 2018
Commitments and Contingencies Disclosure [Abstract]
COMMITMENTS AND CONTINGENT LIABILITIES	COMMITMENTS AND CONTINGENT LIABILITIES The Company is a defendant in various lawsuits considered to be in the normal course of business. Members of the Company's senior legal and financial management teams review litigation on a quarterly and annual basis. The final results of any litigation cannot be predicted with certainty. Although some of this litigation is pending in states where large punitive damages, bearing little relation to the actual damages sustained by plaintiffs, have been awarded in recent years, the Company believes the outcome of pending litigation will not have a material adverse effect on its financial position, results of operations, or cash flows. See Note 3 of the Notes to the Consolidated Financial Statements for details on investment commitments. Guaranty Fund Assessments The United States insurance industry has a policyholder protection system that is monitored and regulated by state insurance departments. These life and health insurance guaranty associations are state entities (in all 50 states as well as Puerto Rico and the District of Columbia) created to protect policyholders of an insolvent insurance company. All insurance companies (with limited exceptions) licensed to sell life or health insurance in a state must be members of that state’s guaranty association. Under state guaranty association laws, certain insurance companies can be assessed (up to prescribed limits) for certain obligations to the policyholders and claimants of impaired or insolvent insurance companies that write the same line or similar lines of business. In 2009, the Pennsylvania Insurance Commissioner placed long-term care insurer Penn Treaty Network America Insurance Company and its subsidiary American Network Insurance Company (collectively referred to as Penn Treaty), neither of which is affiliated with Aflac, in rehabilitation and petitioned a state court for approval to liquidate Penn Treaty. A final order of liquidation was granted by a recognized judicial authority on March 1, 2017, and as a result, Penn Treaty is in the process of liquidation. The Company estimated and recognized the impact of its share of guaranty fund assessments resulting from the liquidation using a discounted rate of 4.25% . The Company recognized a discounted liability for the assessments of $62 million (undiscounted $94 million ), offset by discounted premium tax credits of $48 million (undiscounted $74 million ), for a net $14 million impact to net income in the quarter ended March 31, 2017. The Company paid a majority of these assessments by March 31, 2018, and a majority of the tax credits will be realized over the next four years. The Company used the cost estimate provided as of the liquidation date by the National Organization of Life and Health Guaranty Associations (NOLHGA) to calculate its estimated assessments and tax credits. Guaranty fund assessments for the three-month period ended March 31, 2018 were immaterial.

SUBSEQUENT EVENTS

SUBSEQUENT EVENTS	3 Months Ended
	Mar. 31, 2018
Subsequent Events [Abstract]
SUBSEQUENT EVENTS	SUBSEQUENT EVENTS On April 1, 2018, the Company completed the conversion of Aflac Japan from a branch structure to a legal subsidiary. The treatment of Aflac Japan as a branch for U.S. tax purposes did not change following the completion of this conversion.

SUMMARY OF SIGNIFICANT ACCOUN22

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies)	3 Months Ended
	Mar. 31, 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 as a branch in Japan (Aflac Japan). The conversion of Aflac Japan from a branch to a legal subsidiary was completed on April 1, 2018 (see Note 14), after which date 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 through Aflac Life Insurance Japan Ltd. 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. 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 71% and 69% of the Company's total revenues in the three -month periods ended March 31, 2018 and 2017 , respectively. The percentage of the Company's total assets attributable to Aflac Japan was 85% at March 31, 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 March 31, 2018 , and December 31, 2017 , the consolidated statements of earnings and comprehensive income (loss), shareholders' equity and cash flows for the three -month periods ended March 31, 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).
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 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. The Company elected to early adopt this technical correction and improvement guidance 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. 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. The Company elected to early adopt this guidance 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. 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. The Company adopted this guidance 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. 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 Company adopted this guidance 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, statements of cash flows, or disclosures. 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. The Company adopted this guidance 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, statements of cash flows, 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 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. The Company adopted this guidance 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. 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 Company adopted this guidance 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, statements of cash flows, or disclosures. 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 Company adopted this guidance 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. Statement of Cash Flows - Classification of Certain Cash Receipts and Cash Payment s : In August 2016, the FASB issued amendments that provide guidance on eight specific statement of cash flows classification issues. The Company adopted this guidance 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, statements of cash flows, or 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 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. The Company adopted this guidance as of 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. 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. The Company adopted this guidance 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.
Description of Accounting Pronouncements Pending Adoption	Accounting Pronouncements Pending Adoption Leases - Land Easement Practical Expedient for Transition to Topic 842: In January 2018, 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. Derivatives and Hedging - Targeted Improvements to Accounting for Hedging Activities: In August 2017, 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. 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. 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 Company does not expect the adoption of this guidance to have a significant impact on its financial position, results of operations, or disclosures. 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. 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. 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 March 31, 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.

BUSINESS SEGMENT INFORMATION (T

BUSINESS SEGMENT INFORMATION (Tables)	3 Months Ended
	Mar. 31, 2018
Segment Reporting [Abstract]
Reconciliation of Revenue from Segments to Consolidated	Three Months Ended (In millions) 2018 2017 Revenues: Aflac Japan: Net earned premiums $ 3,263 $ 3,194 Net investment income, less amortized hedge costs (1) 588 557 Other income 12 10 Total Aflac Japan 3,863 3,761 Aflac U.S.: Net earned premiums 1,427 1,390 Net investment income 175 178 Other income 2 1 Total Aflac U.S. 1,604 1,569 Corporate and other (2) 79 67 Total adjusted revenues 5,546 5,397 Realized investment gains (losses) (1),(2) (82 ) (88 ) Total revenues $ 5,464 $ 5,309 (1) Amortized hedge costs related to hedging U.S. dollar-denominated investments held in Aflac Japan were $55 and $52 for the three -month periods ended March 31, 2018 , and 2017 , respectively, and have been reclassified from realized investment gains (losses) and reported as a deduction from net investment income when analyzing segment operations. (2) Amortized hedge costs in Aflac Japan were offset by derivatives entered into as part of corporate activities and resulted in a benefit of $2 for the three -month period ended March 31, 2018 which has been reclassified from realized investment gains (losses) and reported as an increase in net investment income when analyzing operations.
Reconciliation of Adjusted Profit (Loss) from Segments to Consolidated	Three Months Ended (In millions) 2018 2017 Pretax earnings: Aflac Japan (1) $ 818 $ 769 Aflac U.S. 337 310 Corporate and other (2) (46 ) (52 ) Pretax adjusted earnings 1,109 1,027 Realized investment gains (losses) (1),(2),(3) (98 ) (109 ) Other income (loss) (29 ) (20 ) Total earnings before income taxes $ 982 $ 898 Income taxes applicable to pretax adjusted earnings $ 289 $ 351 Effect of foreign currency translation on after-tax 21 5 (1) Amortized hedge costs related to hedging U.S. dollar-denominated investments held in Aflac Japan were $55 and $52 for the three -month periods ended March 31, 2018 , and 2017 , respectively, and have been reclassified from realized investment gains (losses) and reported as a deduction from pretax adjusted earnings when analyzing segment operations. (2) Amortized hedge costs in Aflac Japan were offset by derivatives entered into as part of corporate activities and resulted in a benefit of $2 for the three-month period ended March 31, 2018 which has been reclassified from realized investment gains (losses) and reported as an increase in pretax adjusted earnings when analyzing operations. (3) Excluding a gain of $17 and $21 for the three -month periods ended March 31, 2018 , and 2017 , respectively, related to the interest rate component of the change in fair value of foreign currency swaps on notes payable which is included in adjusted earnings when analyzing segment operations
Reconciliation of Assets from Segment to Consolidated	Assets were as follows: (In millions) March 31, December 31, Assets: Aflac Japan $ 125,174 $ 114,402 Aflac U.S. 19,706 19,893 Corporate and other 2,476 2,922 Total assets $ 147,356 $ 137,217

INVESTMENTS (Tables)

INVESTMENTS (Tables)	3 Months Ended
	Mar. 31, 2018
Available-for-sale Securities	December 31, 2017 (In millions) Cost or Gross Gross Fair Securities available for sale, carried at fair value: Fixed maturity securities: (1) Yen-denominated: Japan government and agencies $ 27,980 $ 3,363 $ 271 $ 31,072 Municipalities 314 28 12 330 Mortgage- and asset-backed securities 242 29 0 271 Public utilities 1,635 352 6 1,981 Sovereign and supranational 1,380 190 1 1,569 Banks/financial institutions 4,742 811 53 5,500 Other corporate 4,085 809 7 4,887 Total yen-denominated 40,378 5,582 350 45,610 U.S dollar-denominated: U.S. government and agencies 146 13 1 158 Municipalities 872 168 0 1,040 Mortgage- and asset-backed securities 161 12 0 173 Public utilities 5,116 884 27 5,973 Sovereign and supranational 267 73 0 340 Banks/financial institutions 2,808 633 8 3,433 Other corporate 25,384 2,620 418 27,586 Total U.S. dollar-denominated 34,754 4,403 454 38,703 Total securities available for sale $ 75,132 (1) $ 9,985 $ 804 $ 84,313 (1) (1) Includes perpetual securities ( $1,462 at amortized cost and $1,789 at fair value) The amortized cost for the Company's investments in debt securities, the cost for equity securities and the fair values of these investments are shown in the following tables. March 31, 2018 (In millions) Cost or Gross Gross Fair Securities available for sale, carried at fair value Fixed maturity securities: (1) Yen-denominated: Japan government and agencies $ 32,961 $ 3,811 $ 192 $ 36,580 Municipalities 350 33 11 372 Mortgage- and asset-backed securities 254 30 0 284 Public utilities 1,739 325 4 2,060 Sovereign and supranational 1,348 212 27 1,533 Banks/financial institutions 5,157 799 76 5,880 Other corporate 4,345 754 8 5,091 Total yen-denominated 46,154 5,964 318 51,800 U.S. dollar-denominated: U.S. government and agencies 148 9 1 156 Municipalities 866 135 0 1,001 Mortgage- and asset-backed securities 165 7 1 171 Public utilities 5,223 631 107 5,747 Sovereign and supranational 274 59 0 333 Banks/financial institutions 2,841 457 34 3,264 Other corporate 25,936 1,736 1,111 26,561 Total U.S. dollar-denominated 35,453 3,034 1,254 37,233 Total securities available for sale $ 81,607 (1) $ 8,998 $ 1,572 $ 89,033 (1) (1) Includes perpetual securities ( $1,506 at amortized cost and $1,774 at fair value) December 31, 2017 (In millions) Fair Equity securities, carried at fair value: Equity securities: Yen-denominated $ 695 U.S. dollar-denominated 328 Total equity securities $ 1,023
Held-to-maturity Securities	March 31, 2018 (In millions) Cost or Gross Gross Fair Securities held to maturity, carried at amortized cost: Fixed maturity securities: Yen-denominated: Japan government and agencies $ 22,686 $ 5,631 $ 0 $ 28,317 Municipalities 379 114 0 493 Mortgage- and asset-backed securities 26 2 0 28 Public utilities 3,508 383 0 3,891 Sovereign and supranational 1,620 299 0 1,919 Banks/financial institutions 2,300 190 13 2,477 Other corporate 2,858 485 0 3,343 Total yen-denominated 33,377 7,104 13 40,468 Total securities held to maturity $ 33,377 $ 7,104 $ 13 $ 40,468 December 31, 2017 (In millions) Cost or Gross Gross Fair Securities held to maturity, carried at amortized cost: Fixed maturity securities: Yen-denominated: Japan government and agencies $ 21,331 $ 5,160 $ 0 $ 26,491 Municipalities 357 105 0 462 Mortgage- and asset-backed securities 26 1 0 27 Public utilities 3,300 398 0 3,698 Sovereign and supranational 1,523 312 0 1,835 Banks/financial institutions 2,206 190 9 2,387 Other corporate 2,687 485 0 3,172 Total yen-denominated 31,430 6,651 9 38,072 Total securities held to maturity $ 31,430 $ 6,651 $ 9 $ 38,072
Equity securities, FV-NI	March 31, 2018 (In millions) Fair Equity securities, carried at fair value through net earnings: Equity securities: (1) Yen-denominated $ 711 U.S. dollar-denominated 397 Total equity securities $ 1,108 (1) (1) Includes perpetual securities ( $71 at fair value)
Investments Classified by Contractual Maturity Date	The contractual and economic maturities of the Company's investments in fixed maturity securities at March 31, 2018 , were as follows: (In millions) Amortized Fair Available for sale: (1) Due in one year or less $ 485 $ 502 Due after one year through five years 9,685 9,551 Due after five years through 10 years 10,637 11,143 Due after 10 years 60,381 67,382 Mortgage- and asset-backed securities 419 455 Total fixed maturity securities available for sale $ 81,607 $ 89,033 Held to maturity: Due in one year or less $ 1,036 $ 1,049 Due after one year through five years 508 527 Due after five years through 10 years 1,597 1,754 Due after 10 years 30,210 37,110 Mortgage- and asset-backed securities 26 28 Total fixed maturity securities held to maturity $ 33,377 $ 40,468 (1) Includes perpetual securities, categorized in accordance with their respective economic maturities (the expected maturity date created by the combination of features in the financial instrument)
Investment Exposures Exceeding Ten Percent Shareholders Equity	Investment exposures that individually exceeded 10% of shareholders' equity were as follows: March 31, 2018 December 31, 2017 (In millions) Credit Amortized Fair Credit Amortized Fair Japan National Government (1) A $54,465 $63,576 A $48,399 $56,532 (1) Japan Government Bonds (JGBs) or JGB-backed securities
Gain (Loss) on Investments	Information regarding pretax realized gains and losses from investments is as follows: Three Months Ended (In millions) 2018 2017 Realized investment gains (losses): Fixed maturity securities: (1) Available for sale: Gross gains from sales $ 9 $ 12 Gross losses from sales (4 ) (15 ) Net gains (losses) from redemptions (2 ) (28 ) Other-than-temporary impairment losses 0 (4 ) Total fixed maturity securities 3 (35 ) Equity securities (2) (46 ) (1) 19 (3) Loan loss reserves (7 ) (1 ) Derivatives and other: Derivative gains (losses) 144 (52 ) Foreign currency gains (losses) (228 ) (71 ) Total derivatives and other (84 ) (123 ) Total realized investment gains (losses) $ (134 ) $ (140 ) (1) Includes perpetual securities (2) See Note 1 of the Notes to the Consolidated Financial Statements for the adoption of accounting guidance on January 1, 2018 related to financial instruments. (3) Includes $6 of impairments
Net Effect on Shareholders' Equity of Unrealized Gains and Losses from Investment Securities	The net effect on shareholders’ equity of unrealized gains and losses from investment securities was as follows: (In millions) March 31, 2018 December 31, Unrealized gains (losses) on securities available for sale $ 7,426 $ 9,358 Deferred income taxes (2,220 ) (3,394 ) Shareholders’ equity, unrealized gains (losses) on investment securities $ 5,206 $ 5,964 See Note 1 for discussion of the accounting treatment of tax on amounts recorded in accumulated other comprehensive income pursuant to the Tax Act and for the adoption of accounting guidance on January 1, 2018 related to financial instruments.
Investments Gross Unrealized Loss Aging	The following tables show the fair values and gross unrealized losses of the Company's available-for-sale and held-to-maturity investments that were in an unrealized loss position, aggregated by investment category and length of time that individual securities have been in a continuous unrealized loss position. March 31, 2018 Total Less than 12 months 12 months or longer (In millions) Fair Unrealized Fair Unrealized Fair Unrealized Fixed maturity securities: (1) U.S. government and U.S. dollar-denominated $ 79 $ 1 $ 71 $ 1 $ 8 $ 0 Japan government and Yen-denominated 4,054 192 128 0 3,926 192 Municipalities: Yen-denominated 128 11 0 0 128 11 Mortgage- and asset- U.S. dollar-denominated 91 1 71 1 20 0 Public utilities: U.S. dollar-denominated 1,649 107 1,095 52 554 55 Yen-denominated 90 4 0 0 90 4 Sovereign and supranational: Yen-denominated 302 27 302 27 0 0 Banks/financial institutions: U.S. dollar-denominated 685 34 596 28 89 6 Yen-denominated 1,467 89 645 14 822 75 Other corporate: U.S. dollar-denominated 13,730 1,111 8,903 420 4,827 691 Yen-denominated 302 8 276 6 26 2 Total $ 22,577 $ 1,585 $ 12,087 $ 549 $ 10,490 $ 1,036 (1) Includes perpetual securities December 31, 2017 Total Less than 12 months 12 months or longer (In millions) Fair Unrealized Fair Unrealized Fair Unrealized Fixed maturity securities: (1) U.S. government and U.S. dollar-denominated $ 74 $ 1 $ 74 $ 1 $ 0 $ 0 Japan government and Yen-denominated 5,255 271 1,264 9 3,991 262 Municipalities: Yen-denominated 129 12 10 0 119 12 Public utilities: U.S. dollar-denominated 785 27 221 3 564 24 Yen-denominated 83 6 0 0 83 6 Sovereign and supranational: Yen-denominated 309 1 309 1 0 0 Banks/financial institutions: U.S. dollar-denominated 362 8 316 5 46 3 Yen-denominated 1,507 62 394 4 1,113 58 Other corporate: U.S. dollar-denominated 7,741 418 2,839 50 4,902 368 Yen-denominated 440 7 349 4 91 3 Total $ 16,685 $ 813 $ 5,776 $ 77 $ 10,909 $ 736 (1) Includes perpetual securities
Other Investments	The table below reflects the composition of the carrying value for other investments as of the periods presented. (In millions) March 31, 2018 December 31, 2017 Other investments: Transitional real estate loans $ 2,719 $ 1,235 Commercial mortgage loans 917 908 Middle market loans 957 859 Policy loans 227 210 Short-term investments 0 57 Other 253 133 Total other investments $ 5,073 $ 3,402
Securities Lending Transactions Accounted for as Secured Borrowings	Details of the Company's securities lending activities were as follows: Securities Lending Transactions Accounted for as Secured Borrowings March 31, 2018 Remaining Contractual Maturity of the Agreements (In millions) Overnight (1) Up to 30 Total Securities lending transactions: Fixed maturity securities: Japan government and agencies $ 0 $ 4,894 $ 4,894 Public utilities 30 0 30 Banks/financial institutions 52 0 52 Other corporate 384 0 384 Equity securities 8 0 8 Total borrowings $ 474 $ 4,894 $ 5,368 Gross amount of recognized liabilities for securities lending transactions $ 5,368 Amounts related to agreements not included in offsetting disclosure in Note 4 $ 0 (1) These securities are pledged as collateral under the Company's U.S. securities lending program and can be called at its discretion; therefore, they are classified as Overnight and Continuous. Securities Lending Transactions Accounted for as Secured Borrowings December 31, 2017 Remaining Contractual Maturity of the Agreements (In millions) Overnight (1) Up to 30 Total Securities lending transactions: Fixed maturity securities: Japan government and agencies $ 0 $ 49 $ 49 Public utilities 73 0 73 Banks/financial institutions 54 0 54 Other corporate 415 0 415 Equity securities 15 0 15 Total borrowings $ 557 $ 49 $ 606 Gross amount of recognized liabilities for securities lending transactions $ 606 Amounts related to agreements not included in offsetting disclosure in Note 4 $ 0 (1) These securities are pledged as collateral under the Company's U.S. securities lending program and can be called at its discretion; therefore, they are classified as Overnight and Continuous.
Variable Interest Entity, Consolidated
Investments in Variable Interest Entities	VIEs - Consolidated The following table presents the cost or amortized cost, fair value and balance sheet caption in which the assets and liabilities of consolidated VIEs are reported. Investments in Consolidated Variable Interest Entities March 31, 2018 December 31, 2017 (In millions) Cost or Amortized Fair Cost or Amortized Fair Assets: Fixed maturity securities, available for sale (1) $ 4,695 $ 5,431 $ 4,538 $ 5,509 Equity securities 760 760 606 753 Other investments (2) 3,994 3,974 2,341 2,328 Other assets (3) 241 241 151 151 Total assets of consolidated VIEs $ 9,690 $ 10,406 $ 7,636 $ 8,741 Liabilities: Other liabilities (3) $ 86 $ 86 $ 128 $ 128 Total liabilities of consolidated VIEs $ 86 $ 86 $ 128 $ 128 (1) Includes perpetual securities (2) Consists of TREs, CMLs, MMLs, and alternative investments in limited partnerships (3) Consists entirely of derivatives
Variable Interest Entity, Not Consolidated
Investments in Variable Interest Entities	VIEs-Not Consolidated The table below reflects the amortized cost, fair value and balance sheet caption in which the Company's investment in VIEs not consolidated are reported. Investments in Variable Interest Entities Not Consolidated March 31, 2018 December 31, 2017 (In millions) Amortized Fair Amortized Fair Assets: Fixed maturity securities, available for sale (1) $ 5,194 $ 5,749 $ 5,004 $ 5,724 Fixed maturity securities, held to maturity 2,711 3,077 2,549 2,929 Other investments 110 108 55 55 Total investments in VIEs not consolidated $ 8,015 $ 8,934 $ 7,608 $ 8,708 (1) Includes perpetual securities

DERIVATIVE INSTRUMENTS (Tables)

DERIVATIVE INSTRUMENTS (Tables)	3 Months Ended
	Mar. 31, 2018
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Schedule of Derivative Instruments in Statement of Financial Position, Fair Value	March 31, 2018 December 31, 2017 (In millions) Asset Liability Asset Liability Hedge Designation/ Derivative Notional Fair Value Fair Value Notional Fair Value Fair Value Cash flow hedges: Foreign currency swaps $ 75 $ 1 $ (2 ) $ 75 $ 0 $ (8 ) Total cash flow hedges 75 1 (2 ) 75 0 (8 ) Fair value hedges: Foreign currency forwards 5,550 244 (5 ) 7,640 2 (221 ) Foreign currency options 9,120 0 (3 ) 7,670 0 (2 ) Total fair value hedges 14,670 244 (8 ) 15,310 2 (223 ) Net investment hedge: Foreign currency forwards 0 0 0 5 0 0 Foreign currency options 0 0 0 434 12 (1 ) Total net investment hedge 0 0 0 439 12 (1 ) Non-qualifying strategies: Foreign currency swaps 5,426 369 (263 ) 5,386 296 (189 ) Foreign currency forwards 6,656 182 (80 ) 3,683 20 (53 ) Foreign currency options 299 0 0 770 0 0 Credit default swaps 94 1 0 88 1 0 Total non-qualifying strategies 12,475 552 (343 ) 9,927 317 (242 ) Total derivatives $ 27,220 $ 797 $ (353 ) $ 25,751 $ 331 $ (474 ) Balance Sheet Location Other assets $ 18,248 $ 797 $ 0 $ 10,948 $ 331 $ 0 Other liabilities 8,972 0 (353 ) 14,803 0 (474 ) Total derivatives $ 27,220 $ 797 $ (353 ) $ 25,751 $ 331 $ (474 )
Schedule of Fair Value Hedging Instruments, Statements of Financial Performance and Financial Position, Location	The following table presents the gains and losses on derivatives and the related hedged items in fair value hedges. Fair Value Hedging Relationships (In millions) Hedging Derivatives Hedged Items Hedging Derivatives Hedged Items Total Gains (Losses) Gains (Losses) Gains (Losses) Ineffectiveness Three Months Ended March 31, 2018: Foreign currency Fixed maturity securities $ 414 $ (39 ) $ 453 $ (464 ) $ (11 ) Foreign currency Fixed maturity securities (1 ) (1 ) 0 0 0 Three Months Ended March 31, 2017: Foreign currency forwards Fixed maturity and equity securities $ 341 $ (48 ) $ 389 $ (372 ) $ 17 Foreign currency options Fixed maturity securities 24 13 11 (10 ) 1
Schedule of Derivative Instruments, Gain (Loss) in Statement of Financial Performance	The following table summarizes the impact to realized investment gains (losses) and other comprehensive income (loss) from all derivatives and hedging instruments. Three Months Ended March 31, 2018 2017 (In millions) Realized Investment Other (1) Realized Investment Other (1) Qualifying hedges: Cash flow hedges: Foreign currency swaps $ 1 $ 6 $ 0 $ 2 Total cash flow hedges 1 6 0 2 Fair value hedges: Foreign currency forwards (2) (50 ) 0 (31 ) 0 Foreign currency options (2) (1 ) 0 14 0 Total fair value hedges (51 ) 0 (17 ) 0 Net investment hedge: Non-derivative hedging instruments 0 (84 ) 0 (17 ) Foreign currency forwards 0 0 0 (9 ) Foreign currency options 0 (8 ) 0 (23 ) Total net investment hedge 0 (92 ) 0 (49 ) Non-qualifying strategies: Foreign currency swaps 14 0 (8 ) 0 Foreign currency forwards 179 0 (27 ) 0 Foreign currency options 1 0 0 0 Total non-qualifying strategies 194 0 (35 ) 0 Total $ 144 $ (86 ) $ (52 ) $ (47 ) (1) Cash flow hedge items are recorded as unrealized gains (losses) on derivatives and net investment hedge items are recorded in the unrealized foreign currency translation gains (losses) line in the consolidated statement of comprehensive income (loss). (2) Impact shown net of effect of hedged items (see Fair Value Hedges section of this Note 4 for further detail)
Fair Value and Notional Amount of Derivatives with Counterparty Credit Risk	The counterparties to these derivatives are financial institutions with the following credit ratings: March 31, 2018 December 31, 2017 (In millions) Notional Amount Asset Derivatives Liability Derivatives Notional Amount Asset Derivatives Liability Derivatives Counterparties' credit rating: AA $ 4,685 $ 123 $ (12 ) $ 4,708 $ 52 $ (37 ) A 22,081 673 (290 ) 20,604 271 (370 ) BBB 454 1 (51 ) 439 8 (67 ) Total $ 27,220 $ 797 $ (353 ) $ 25,751 $ 331 $ (474 )
Offsetting Assets	Offsetting of Financial Assets and Derivative Asset March 31, 2018 Gross Amounts Not Offset (In millions) Gross Amount of Recognized Assets Gross Amount Offset in Balance Sheet Net Amount of Assets Presented in Balance Sheet Financial Instruments Securities Collateral Cash Collateral Received Net Amount Derivative assets: Derivative assets subject to a master netting agreement or offsetting arrangement $ 556 $ 0 $ 556 $ (116 ) $ (343 ) $ (67 ) $ 30 Derivative assets not subject to a master netting agreement or offsetting arrangement 241 241 241 Total derivative assets 797 0 797 (116 ) (343 ) (67 ) 271 Securities lending and similar arrangements 5,249 0 5,249 0 0 (5,249 ) 0 Total $ 6,046 $ 0 $ 6,046 $ (116 ) $ (343 ) $ (5,316 ) $ 271 December 31, 2017 Gross Amounts Not Offset (In millions) Gross Amount of Recognized Assets Gross Amount Offset in Balance Sheet Net Amount of Assets Presented in Balance Sheet Financial Instruments Securities Collateral Cash Collateral Received Net Amount Derivative assets: Derivative assets subject to a master netting agreement or offsetting arrangement $ 180 $ 0 $ 180 $ (82 ) $ 0 $ (98 ) $ 0 Derivative assets not subject to a master netting agreement or offsetting arrangement 151 151 151 Total derivative assets 331 0 331 (82 ) 0 (98 ) 151 Securities lending and similar arrangements 592 0 592 0 0 (592 ) 0 Total $ 923 $ 0 $ 923 $ (82 ) $ 0 $ (690 ) $ 151
Offsetting Liabilities	Offsetting of Financial Liabilities and Derivative Liabilities March 31, 2018 Gross Amounts Not Offset (In millions) Gross Amount of Recognized Liabilities Gross Amount Offset in Balance Sheet Net Amount of Liabilities Presented in Balance Sheet Financial Instruments Securities Collateral Cash Collateral Pledged Net Amount Derivative liabilities: Derivative liabilities subject to a master netting agreement or offsetting arrangement $ (267 ) $ 0 $ (267 ) $ 116 $ 36 $ 113 $ (2 ) Derivative liabilities not subject to a master netting agreement or offsetting arrangement (86 ) (86 ) (86 ) Total derivative liabilities (353 ) 0 (353 ) 116 36 113 (88 ) Securities lending and similar arrangements (5,368 ) 0 (5,368 ) 5,249 0 0 (119 ) Total $ (5,721 ) $ 0 $ (5,721 ) $ 5,365 $ 36 $ 113 $ (207 ) December 31, 2017 Gross Amounts Not Offset (In millions) Gross Amount of Recognized Liabilities Gross Amount Offset in Balance Sheet Net Amount of Liabilities Presented in Balance Sheet Financial Instruments Securities Collateral Cash Collateral Pledged Net Amount Derivative liabilities: Derivative liabilities subject to a master netting agreement or offsetting arrangement $ (346 ) $ 0 $ (346 ) $ 82 $ 245 $ 10 $ (9 ) Derivative liabilities not subject to a master netting agreement or offsetting arrangement (128 ) (128 ) (128 ) Total derivative liabilities (474 ) 0 (474 ) 82 245 10 (137 ) Securities lending and similar arrangements (606 ) 0 (606 ) 592 0 0 (14 ) Total $ (1,080 ) $ 0 $ (1,080 ) $ 674 $ 245 $ 10 $ (151 )

FAIR VALUE MEASUREMENTS (Tables

FAIR VALUE MEASUREMENTS (Tables)	3 Months Ended
	Mar. 31, 2018
Fair Value Disclosures [Abstract]
Fair Value Hierarchy, Assets and Liabilities Measured on Recurring Basis	The following tables present the fair value hierarchy levels of the Company's assets and liabilities that are measured and carried at fair value on a recurring basis. March 31, 2018 (In millions) Quoted Prices in Significant Significant Total Assets: Securities available for sale, carried at Fixed maturity securities: (1) Government and agencies $ 35,325 $ 1,411 $ 0 $ 36,736 Municipalities 0 1,373 0 1,373 Mortgage- and asset-backed securities 0 269 186 455 Public utilities 0 7,724 83 7,807 Sovereign and supranational 0 1,866 0 1,866 Banks/financial institutions 0 9,120 24 9,144 Other corporate 0 31,509 143 31,652 Total fixed maturity securities 35,325 53,272 436 89,033 (1) Equity securities (1) 1,015 77 16 1,108 (1) Cash and cash equivalents 4,080 0 0 4,080 Other assets: Foreign currency swaps 0 130 240 370 Foreign currency forwards 0 426 0 426 Credit default swaps 0 0 1 1 Total other assets 0 556 241 797 Total assets $ 40,420 $ 53,905 $ 693 $ 95,018 Liabilities: Other liabilities: Foreign currency swaps $ 0 $ 179 $ 86 $ 265 Foreign currency forwards 0 85 0 85 Foreign currency options 0 3 0 3 Total liabilities $ 0 $ 267 $ 86 $ 353 (1) Includes perpetual securities December 31, 2017 (In millions) Quoted Prices in Significant Significant Total Assets: Securities available for sale, carried at Fixed maturity securities: (1) Government and agencies $ 30,109 $ 1,121 $ 0 $ 31,230 Municipalities 0 1,370 0 1,370 Mortgage- and asset-backed securities 0 269 175 444 Public utilities 0 7,886 68 7,954 Sovereign and supranational 0 1,909 0 1,909 Banks/financial institutions 0 8,908 25 8,933 Other corporate 0 32,327 146 32,473 Total fixed maturity securities 30,109 53,790 414 84,313 (1) Equity securities 1,001 6 16 1,023 Other investments 57 0 0 57 Cash and cash equivalents 3,491 0 0 3,491 Other assets: Foreign currency swaps 0 146 150 296 Foreign currency forwards 0 22 0 22 Foreign currency options 0 12 0 12 Credit default swaps 0 0 1 1 Total other assets 0 180 151 331 Total assets $ 34,658 $ 53,976 $ 581 $ 89,215 Liabilities: Other liabilities: Foreign currency swaps $ 0 $ 69 $ 128 $ 197 Foreign currency forwards 0 274 0 274 Foreign currency options 0 3 0 3 Total liabilities $ 0 $ 346 $ 128 $ 474 (1) Includes perpetual securities
Fair Value Hierarchy Levels of Assets and Liabilities Carried at Cost or Amortized Cost	The following tables present the carrying amount and fair value categorized by fair value hierarchy level for the Company's financial instruments that are not carried at fair value. March 31, 2018 (In millions) Carrying Quoted Prices in Significant Significant Total Assets: Securities held to maturity, Fixed maturity securities: Government and agencies $ 22,686 $ 28,317 $ 0 $ 0 $ 28,317 Municipalities 379 0 493 0 493 Mortgage and asset-backed 26 0 9 19 28 Public utilities 3,508 0 3,891 0 3,891 Sovereign and 1,620 0 1,919 0 1,919 Banks/financial institutions 2,300 0 2,477 0 2,477 Other corporate 2,858 0 3,343 0 3,343 Other investments (1) 4,608 0 15 4,575 4,590 Total assets $ 37,985 $ 28,317 $ 12,147 $ 4,594 $ 45,058 Liabilities: Other policyholders’ funds $ 7,417 $ 0 $ 0 $ 7,307 $ 7,307 Notes payable 5,352 0 5,146 281 5,427 Total liabilities $ 12,769 $ 0 $ 5,146 $ 7,588 $ 12,734 (1) Excludes policy loans of $227 and equity method investments of $238 , at carrying value December 31, 2017 (In millions) Carrying Quoted Prices in Significant Significant Total Assets: Securities held to maturity, Fixed maturity securities: Government and agencies $ 21,331 $ 26,491 $ 0 $ 0 $ 26,491 Municipalities 357 0 462 0 462 Mortgage and asset-backed 26 0 8 19 27 Public utilities 3,300 0 3,698 0 3,698 Sovereign and 1,523 0 1,835 0 1,835 Banks/financial institutions 2,206 0 2,387 0 2,387 Other corporate 2,687 0 3,172 0 3,172 Other investments (1) 3,017 0 15 2,987 3,002 Total assets $ 34,447 $ 26,491 $ 11,577 $ 3,006 $ 41,074 Liabilities: Other policyholders’ funds $ 6,939 $ 0 $ 0 $ 6,841 $ 6,841 Notes payable 5,267 0 5,288 265 5,553 Total liabilities $ 12,206 $ 0 $ 5,288 $ 7,106 $ 12,394 (1) Excludes policy loans of $210 and equity method investments of $118 , at carrying value
Fair Value Assets Securities Carried At Fair Value Primary Pricing Sources	The following tables present the pricing sources for the fair values of the Company's fixed maturity and equity securities. March 31, 2018 (In millions) Quoted Prices in Active Markets for Identical Assets Significant Observable Inputs Significant Unobservable Inputs Total Securities available for sale, carried at fair value: Fixed maturity securities: (1) Government and agencies: Third party pricing vendor $ 35,325 $ 1,411 $ 0 $ 36,736 Total government and agencies 35,325 1,411 0 36,736 Municipalities: Third party pricing vendor 0 1,373 0 1,373 Total municipalities 0 1,373 0 1,373 Mortgage- and asset-backed securities: Third party pricing vendor 0 269 0 269 Broker/other 0 0 186 186 Total mortgage- and asset-backed securities 0 269 186 455 Public utilities: Third party pricing vendor 0 7,724 0 7,724 Broker/other 0 0 83 83 Total public utilities 0 7,724 83 7,807 Sovereign and supranational: Third party pricing vendor 0 1,866 0 1,866 Total sovereign and supranational 0 1,866 0 1,866 Banks/financial institutions: Third party pricing vendor 0 9,120 0 9,120 Broker/other 0 0 24 24 Total banks/financial institutions 0 9,120 24 9,144 Other corporate: Third party pricing vendor 0 31,509 0 31,509 Broker/other 0 0 143 143 Total other corporate 0 31,509 143 31,652 Total securities available for sale $ 35,325 $ 53,272 $ 436 $ 89,033 (1) Equity securities, carried at fair value: (1) Third party pricing vendor $ 1,015 $ 77 $ 0 $ 1,092 Broker/other 0 0 16 16 Total equity securities $ 1,015 $ 77 $ 16 $ 1,108 (1) (1) Includes perpetual securities December 31, 2017 (In millions) Quoted Prices in Active Markets Significant Observable Significant Unobservable Inputs Total Securities available for sale, carried at fair value: Fixed maturity securities: (1) Government and agencies: Third party pricing vendor $ 30,109 $ 1,121 $ 0 $ 31,230 Total government and agencies 30,109 1,121 0 31,230 Municipalities: Third party pricing vendor 0 1,370 0 1,370 Total municipalities 0 1,370 0 1,370 Mortgage- and asset-backed securities: Third party pricing vendor 0 269 0 269 Broker/other 0 0 175 175 Total mortgage- and asset-backed securities 0 269 175 444 Public utilities: Third party pricing vendor 0 7,886 0 7,886 Broker/other 0 0 68 68 Total public utilities 0 7,886 68 7,954 Sovereign and supranational: Third party pricing vendor 0 1,807 0 1,807 Broker/other 0 102 0 102 Total sovereign and supranational 0 1,909 0 1,909 Banks/financial institutions: Third party pricing vendor 0 8,908 0 8,908 Broker/other 0 0 25 25 Total banks/financial institutions 0 8,908 25 8,933 Other corporate: Third party pricing vendor 0 32,327 0 32,327 Broker/other 0 0 146 146 Total other corporate 0 32,327 146 32,473 Total securities available for sale $ 30,109 $ 53,790 $ 414 $ 84,313 (1) Equity securities, carried at fair value: Third party pricing vendor $ 1,001 $ 6 $ 0 $ 1,007 Broker/other 0 0 16 16 Total equity securities $ 1,001 $ 6 $ 16 $ 1,023 (1) Includes perpetual securities
Fair Value Assets Held-To-Maturity Securities Primary Pricing Sources	December 31, 2017 (In millions) Quoted Prices in Active Markets Significant Observable Significant Unobservable Inputs Total Securities held to maturity, carried at amortized cost: Fixed maturity securities: Government and agencies: Third party pricing vendor $ 26,491 $ 0 $ 0 $ 26,491 Total government and agencies 26,491 0 0 26,491 Municipalities: Third party pricing vendor 0 462 0 462 Total municipalities 0 462 0 462 Mortgage- and asset-backed securities: Third party pricing vendor 0 8 0 8 Broker/other 0 0 19 19 Total mortgage- and asset-backed securities 0 8 19 27 Public utilities: Third party pricing vendor 0 3,698 0 3,698 Total public utilities 0 3,698 0 3,698 Sovereign and supranational: Third party pricing vendor 0 1,835 0 1,835 Total sovereign and supranational 0 1,835 0 1,835 Banks/financial institutions: Third party pricing vendor 0 2,387 0 2,387 Total banks/financial institutions 0 2,387 0 2,387 Other corporate: Third party pricing vendor 0 3,172 0 3,172 Total other corporate 0 3,172 0 3,172 Total securities held to maturity $ 26,491 $ 11,562 $ 19 $ 38,072 March 31, 2018 (In millions) Quoted Prices in Active Markets for Identical Assets Significant Observable Inputs Significant Unobservable Inputs Total Securities held to maturity, carried at amortized cost: Fixed maturity securities: Government and agencies: Third party pricing vendor $ 28,317 $ 0 $ 0 $ 28,317 Total government and agencies 28,317 0 0 28,317 Municipalities: Third party pricing vendor 0 493 0 493 Total municipalities 0 493 0 493 Mortgage- and asset-backed securities: Third party pricing vendor 0 9 0 9 Broker/other 0 0 19 19 Total mortgage- and asset-backed securities 0 9 19 28 Public utilities: Third party pricing vendor 0 3,891 0 3,891 Total public utilities 0 3,891 0 3,891 Sovereign and supranational: Third party pricing vendor 0 1,919 0 1,919 Total sovereign and supranational 0 1,919 0 1,919 Banks/financial institutions: Third party pricing vendor 0 2,477 0 2,477 Total banks/financial institutions 0 2,477 0 2,477 Other corporate: Third party pricing vendor 0 3,343 0 3,343 Total other corporate 0 3,343 0 3,343 Total securities held to maturity $ 28,317 $ 12,132 $ 19 $ 40,468
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation	Transfers between Hierarchy Levels and Level 3 Rollforward During the three -month periods ended March 31, 2018 and 2017 , respectively, there were no transfers between Level 1 and 2 for assets and liabilities that are measured and carried at fair value on a recurring basis. The following tables present the changes in fair value of the Company's investments and derivatives carried at fair value classified as Level 3. Three Months Ended Fixed Maturity Securities Equity Derivatives (1) (In millions) Mortgage- Public Banks/ Other Foreign Credit Total Balance, beginning of period $ 175 $ 68 $ 25 $ 146 $ 16 $ 22 $ 1 $ 453 Realized investment gains (losses) included 0 0 0 0 0 126 0 126 Unrealized gains (losses) included in other 11 (1 ) (1 ) (2 ) 0 6 0 13 Purchases, issuances, sales and settlements: Purchases 0 16 0 0 0 0 0 16 Issuances 0 0 0 0 0 0 0 0 Sales 0 0 0 0 0 0 0 0 Settlements 0 0 0 (1 ) 0 0 0 (1 ) Transfers into Level 3 0 0 0 0 0 0 0 0 Transfers out of Level 3 0 0 0 0 0 0 0 0 Balance, end of period $ 186 $ 83 $ 24 $ 143 $ 16 $ 154 $ 1 $ 607 Changes in unrealized gains (losses) relating $ 0 $ 0 $ 0 $ 0 $ 0 $ 126 $ 0 $ 126 (1) Derivative assets and liabilities are presented net Three Months Ended Fixed Maturity Securities Equity Derivatives (1) (In millions) Mortgage- Public Banks/ Other Foreign Credit Total Balance, beginning of period $ 198 $ 16 $ 25 $ 0 $ 3 $ (21 ) $ 2 $ 223 Realized investment gains (losses) included in earnings 0 0 0 0 0 38 0 38 Unrealized gains (losses) included in other comprehensive income (loss) 6 0 (1 ) 0 0 2 0 7 Purchases, issuances, sales and settlements: Purchases 0 0 0 35 2 0 0 37 Issuances 0 0 0 0 0 0 0 0 Sales 0 0 0 0 (1 ) 0 0 (1 ) Settlements (9 ) 0 0 0 0 0 0 (9 ) Transfers into Level 3 0 0 0 0 0 0 0 0 Transfers out of Level 3 0 0 0 0 0 0 0 0 Balance, end of period $ 195 $ 16 $ 24 $ 35 $ 4 $ 19 $ 2 $ 295 Changes in unrealized gains (losses) relating $ 0 $ 0 $ 0 $ 0 $ 0 $ 38 $ 0 $ 38 (1) Derivative assets and liabilities are presented net
Fair Value Inputs, Assets, Quantitative Information	December 31, 2017 (In millions) Fair Value Valuation Technique(s) Unobservable Input Range Assets: Securities available for sale, carried at fair value: Fixed maturity securities: Mortgage- and asset-backed securities $ 175 Consensus pricing Offered quotes N/A (c) Public utilities 68 Discounted cash flow Credit spreads N/A (c) Banks/financial institutions 25 Consensus pricing Offered quotes N/A (c) Other corporate 146 Discounted cash flow Credit spreads N/A (c) Equity securities 16 Net asset value Offered quotes N/A (c) Other assets: Foreign currency swaps 80 Discounted cash flow Interest rates (USD) 2.40% - 2.54% (a) Interest rates (JPY) .26% - .85% (b) CDS spreads 9 - 90 bps 70 Discounted cash flow Interest rates (USD) 2.40% - 2.54% (a) Interest rates (JPY) .26% - .85% (b) Credit default swaps 1 Discounted cash flow Base correlation 46.33% - 49.65% (d) CDS spreads 25 bps Recovery rate 37.24% Total assets $ 581 (a) Inputs derived from U.S. long-term rates to accommodate long maturity nature of the Company's swaps (b) Inputs derived from Japan long-term rates to accommodate long maturity nature of the Company's swaps (c) N/A represents securities where the Company receives unadjusted broker quotes and for which there is no transparency into the providers' valuation techniques or unobservable inputs. (d) Range of base correlation for the Company's bespoke tranche for attachment and detachment points corresponding to market indices The following tables summarize the significant unobservable inputs used in the valuation of the Company's Level 3 investments and derivatives carried at fair value. Included in the tables are the inputs or range of possible inputs that have an effect on the overall valuation of the financial instruments. March 31, 2018 (In millions) Fair Value Valuation Technique(s) Unobservable Input Range Assets: Securities available for sale, carried at fair value: Fixed maturity securities: Mortgage- and asset-backed securities $ 186 Consensus pricing Offered quotes N/A (c) Public utilities 83 Discounted cash flow Credit spreads N/A (c) Banks/financial institutions 24 Consensus pricing Offered quotes N/A (c) Other corporate 143 Discounted cash flow Credit spreads N/A (c) Equity securities 16 Net asset value Offered quotes N/A (c) Other assets: Foreign currency swaps 185 Discounted cash flow Interest rates (USD) 2.78% - 2.82% (a) Interest rates (JPY) .26% - .85% (b) CDS spreads 13 - 101 bps 55 Discounted cash flow Interest rates (USD) 2.78% - 2.82% (a) Interest rates (JPY) .26% - .85% (b) Credit default swaps 1 Discounted cash flow Base correlation 49.98% - 54.13% (d) CDS spreads 15 bps Recovery rate 37.24% Total assets $ 693 (a) Inputs derived from U.S. long-term rates to accommodate long maturity nature of the Company's swaps (b) Inputs derived from Japan long-term rates to accommodate long maturity nature of the Company's swaps (c) N/A represents securities where the Company receives unadjusted broker quotes and for which there is no transparency into the providers' valuation techniques or unobservable inputs. (d) Range of base correlation for the Company's bespoke tranche for attachment and detachment points corresponding to market indices
Fair Value Inputs, Liabilities, Quantitative Information	December 31, 2017 (In millions) Fair Value Valuation Technique(s) Unobservable Input Range Liabilities: Other liabilities: Foreign currency swaps $ 120 Discounted cash flow Interest rates (USD) 2.40% - 2.54% (a) Interest rates (JPY) .26% - .85% (b) CDS spreads 13 - 157 bps 8 Discounted cash flow Interest rates (USD) 2.40% - 2.54% (a) Interest rates (JPY) .26% - .85% (b) Total liabilities $ 128 (a) Inputs derived from U.S. long-term rates to accommodate long maturity nature of the Company's swaps (b) Inputs derived from Japan long-term rates to accommodate long maturity nature of the Company's swaps March 31, 2018 (In millions) Fair Value Valuation Technique(s) Unobservable Input Range Liabilities: Other liabilities: Foreign currency swaps $ 84 Discounted cash flow Interest rates (USD) 2.78% - 2.82% (a) Interest rates (JPY) .26% - .85% (b) CDS spreads 17 - 170 bps 2 Discounted cash flow Interest rates (USD) 2.78% - 2.82% (a) Interest rates (JPY) .26% - .85% (b) Total liabilities $ 86 (a) Inputs derived from U.S. long-term rates to accommodate long maturity nature of the Company's swaps (b) Inputs derived from Japan long-term rates to accommodate long maturity nature of the Company's swap

POLICY LIABILITIES (Tables)

POLICY LIABILITIES (Tables)	3 Months Ended
	Mar. 31, 2018
Insurance Loss Reserves [Abstract]
Schedule of Liability for Unpaid Claims Adjustment Expense	Changes in the liability for unpaid policy claims were as follows: Three Months Ended (In millions) 2018 2017 Unpaid supplemental health claims, beginning of period $ 3,884 $ 3,707 Less reinsurance recoverables 30 27 Net balance, beginning of period 3,854 3,680 Add claims incurred during the period related to: Current year 1,842 1,737 Prior years (192 ) (111 ) Total incurred 1,650 1,626 Less claims paid during the period on claims incurred during: Current year 518 505 Prior years 1,116 1,055 Total paid 1,634 1,560 Effect of foreign exchange rate changes on unpaid claims 142 80 Net balance, end of period 4,012 3,826 Add reinsurance recoverables 31 29 Unpaid supplemental health claims, end of period 4,043 3,855 Unpaid life claims, end of period 587 375 Total liability for unpaid policy claims $ 4,630 $ 4,230

REINSURANCE (Tables)

REINSURANCE (Tables)	3 Months Ended
	Mar. 31, 2018
Reinsurance Disclosures [Abstract]
Effects of Reinsurance	The following table reconciles direct premium income and direct benefits and claims to net amounts after the effect of reinsurance. Three Months Ended (In millions) 2018 2017 Direct premium income $ 4,833 $ 4,724 Ceded to other companies: Ceded Aflac Japan closed blocks (129 ) (130 ) Other (15 ) (12 ) Assumed from other companies: Retrocession activities 54 54 Other 2 2 Net premium income $ 4,745 $ 4,638 Direct benefits and claims $ 3,119 $ 3,129 Ceded benefits and change in reserves for future benefits: Ceded Aflac Japan closed blocks (117 ) (122 ) Eliminations 12 13 Other (12 ) (11 ) Assumed from other companies: Retrocession activities 52 54 Eliminations (12 ) (13 ) Other 0 2 Benefits and claims, net $ 3,042 $ 3,052

NOTES PAYABLE (Tables)

NOTES PAYABLE (Tables)	3 Months Ended
	Mar. 31, 2018
Debt Disclosure [Abstract]
Schedule of Long-term Debt Instruments	A summary of notes payable follows: (In millions) March 31, 2018 December 31, 2017 2.40% senior notes due March 2020 $ 548 $ 548 4.00% senior notes due February 2022 348 348 3.625% senior notes due June 2023 697 697 3.625% senior notes due November 2024 746 745 3.25% senior notes due March 2025 446 446 2.875% senior notes due October 2026 297 297 6.90% senior notes due December 2039 220 220 6.45% senior notes due August 2040 254 254 4.00% senior notes due October 2046 394 394 Yen-denominated senior notes and subordinated debentures: .932% senior notes due January 2027 (principal amount 60.0 billion yen) 562 528 2.108% subordinated debentures due October 2047 (principal amount 60.0 billion yen) 559 526 Yen-denominated loans: Variable interest rate loan due September 2021 (.32% in 2018 and 2017, principal amount 5.0 billion yen) 47 44 Variable interest rate loan due September 2023 (.47% in 2018 and 2017, principal amount 25.0 billion yen) 234 220 Capitalized lease obligations payable through 2025 20 22 Total notes payable $ 5,372 $ 5,289 Amounts in the table above are reported net of debt issuance costs and issuance premiums or discounts, if applicable, that are being amortized over the life of the notes.
Schedule of Line of Credit Facilities	A summary of the Company's lines of credit as of March 31, 2018 follows: Borrower Type Original Term Expiration Date Capacity Amount Outstanding Interest Rate on Borrowed Amount Maturity Period Commitment Fee Business Purpose Aflac Incorporated uncommitted bilateral 364 days November 30, 2018 $100 million $0 million The rate quoted by the bank and agreed upon at the time of borrowing Up to 3 months None General corporate purposes Aflac Incorporated unsecured revolving 3 years March 31, 2019, or the date commitments are terminated pursuant to an event of default 100.0 billion yen 0.0 billion yen A rate per annum equal to (a) Tokyo interbank market rate (TIBOR) plus, the alternative applicable TIBOR margin during the availability period from the closing date to the commitment termination date or (b) the TIBOR rate offered by the agent to major banks in yen for the applicable period plus, the applicable alternative TIBOR margin during the term out period No later than .30% to .50%, depending on the Parent Company's debt ratings as of the date of determination General corporate purposes, including a capital contingency plan for the operations of the Parent Company Aflac Incorporated unsecured revolving 5 years September 18, 2020, or the date commitments are terminated pursuant to an event of default (1) 55.0 billion yen, or the equivalent amount in U.S. dollars 0.0 billion yen A rate per annum equal to, at the Company's option, either, (a) London Interbank Offered Rate (LIBOR) adjusted for certain costs or (b) a base rate determined by reference to the highest of (1) the federal funds rate plus 1/2 of 1%, (2) the rate of interest for such day announced by Mizuho Bank, Ltd. as its prime rate, or (3) the eurocurrency rate for an interest period of one month plus 1.00%, in each case plus an applicable margin No later than September 18, 2020 (1) .085% to .225%, depending on the Parent Company's debt ratings as of the date of determination General corporate purposes, including a capital contingency plan for the operations of the Parent Company Aflac Incorporated uncommitted bilateral None specified None specified $50 million $0 million A rate per annum equal to, at the Parent Company's option, either (a) a eurocurrency rate determined by reference to the agent's LIBOR for the interest period relevant to such borrowing or (b) the base rate determined by reference to the greater of (i) the prime rate as determined by the agent, and (ii) the sum of 0.50% and the federal funds rate for such day Up to 3 months None General corporate purposes Aflac (2) uncommitted revolving 364 days November 30, 2018 $250 million $0 million USD three-month LIBOR plus 75 basis points per annum 3 months None General corporate purposes Aflac Incorporated (2) uncommitted revolving 364 days April 2, 2018 37.5 billion yen 0.0 billion yen Three-month TIBOR plus 80 basis points per annum 3 months None General corporate purposes (1) Expiration and maturity period dates were updated in April 2018 to April 4, 2023 (2) Intercompany credit agreement

SHAREHOLDERS' EQUITY (Tables)

SHAREHOLDERS' EQUITY (Tables)	3 Months Ended
	Mar. 31, 2018
Stockholders' Equity Note [Abstract]
Schedule of Common Stock Outstanding Roll Forward	The following table is a reconciliation of the number of shares of the Company's common stock for the three -month periods ended March 31 . (In thousands of shares) 2018 2017 Common stock - issued: Balance, beginning of period 1,345,762 1,342,498 Exercise of stock options and issuance of restricted shares 1,014 868 Balance, end of period 1,346,776 1,343,366 Treasury stock: Balance, beginning of period 564,852 530,877 Purchases of treasury stock: Open market 6,640 16,986 Other 315 288 Dispositions of treasury stock: Shares issued to AFL Stock Plan (384 ) (494 ) Exercise of stock options (305 ) (256 ) Other (99 ) (40 ) Balance, end of period 571,019 547,361 Shares outstanding, end of period 775,757 796,005
Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share	The following table presents the approximate number of share-based awards to purchase shares, on a weighted-average basis, that were considered to be anti-dilutive and were excluded from the calculation of diluted earnings per share for the following periods. Three Months Ended (In thousands) 2018 2017 Anti-dilutive share-based awards 9 642
Schedule of Accumulated Other Comprehensive Income (Loss)	Reclassifications from Accumulated Other Comprehensive Income The tables below are reconciliations of accumulated other comprehensive income by component for the following periods. Changes in Accumulated Other Comprehensive Income Three Months Ended (In millions) Unrealized Foreign Unrealized Unrealized Pension Total Balance, beginning of period $ (1,750 ) $ 5,964 $ (23 ) $ (163 ) $ 4,028 Other comprehensive 447 (983 ) 2 (37 ) (571 ) Amounts reclassified from 0 225 (1) 0 3 228 Net current-period other 447 (758 ) 2 (34 ) (343 ) Balance, end of period $ (1,303 ) $ 5,206 $ (21 ) $ (197 ) $ 3,685 (1) Includes amounts reclassified due to changes in accounting principles of $(148) related to financial instruments and $374 related to tax effects from tax reform All amounts in the table above are net of tax. Three Months Ended (In millions) Unrealized Foreign Unrealized Unrealized Pension Liability Adjustment Total Balance, beginning of period $ (1,983 ) $ 4,805 $ (24 ) $ (168 ) $ 2,630 Other comprehensive 333 (341 ) 2 (4 ) (10 ) Amounts reclassified from 0 10 0 2 12 Net current-period other 333 (331 ) 2 (2 ) 2 Balance, end of period $ (1,650 ) $ 4,474 $ (22 ) $ (170 ) $ 2,632 All amounts in the table above are net of tax.
Reclassification Out Of Accumulated Other Comprehensive Income	The tables below summarize the amounts reclassified from each component of accumulated other comprehensive income into net earnings for the following periods. Reclassifications Out of Accumulated Other Comprehensive Income (In millions) Three Months Ended Details about Accumulated Other Comprehensive Income Components Amount Reclassified from Accumulated Other Comprehensive Income Affected Line Item in the Unrealized gains (losses) on available-for-sale $ 2 Sales and redemptions 0 Other-than-temporary impairment 2 Total before tax (1 ) Tax (expense) or benefit (1) $ 1 Net of tax Amortization of defined benefit pension items: Actuarial gains (losses) $ (4 ) Acquisition and operating expenses (2) Prior service (cost) credit 0 Acquisition and operating expenses (2) 1 Tax (expense) or benefit (1) $ (3 ) Net of tax Total reclassifications for the period $ (2 ) Net of tax (1) Based on 27% blended tax rate (2) These accumulated other comprehensive income components are included in the computation of net periodic pension cost (see Note 12 for additional details). (In millions) Three Months Ended Details about Accumulated Other Comprehensive Income Components Amount Reclassified from Accumulated Other Comprehensive Income Affected Line Item in the Unrealized gains (losses) on available-for-sale $ (6 ) Sales and redemptions (10 ) Other-than-temporary impairment (16 ) Total before tax 6 Tax (expense) or benefit (1) $ (10 ) Net of tax Amortization of defined benefit pension items: Actuarial gains (losses) $ (3 ) Acquisition and operating expenses (2) Prior service (cost) credit 0 Acquisition and operating expenses (2) 1 Tax (expense) or benefit (1) $ (2 ) Net of tax Total reclassifications for the period $ (12 ) Net of tax (1) Based on 35% tax rate (2) These accumulated other comprehensive income components are included in the computation of net periodic pension cost (see Note 12 for additional details)

SHARE-BASED COMPENSATION (Table

SHARE-BASED COMPENSATION (Tables)	3 Months Ended
	Mar. 31, 2018
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock Options Outstanding and Exercisable	The following table provides information on stock options outstanding and exercisable at March 31, 2018 . Stock Weighted-Average Aggregate Weighted-Average Outstanding 6,306 5.5 $ 99 $ 28.03 Exercisable 4,439 4.4 77 26.45
Schedule of Nonvested Restricted Stock Units Activity	The following table summarizes restricted stock activity during the three -month period ended March 31 . (In thousands of shares) Shares Weighted-Average Grant-Date Fair Value Per Share Restricted stock at December 31, 2017 3,635 $ 32.40 Granted in 2018 918 44.12 Canceled in 2018 (56 ) 33.18 Vested in 2018 (980 ) 31.50 Restricted stock at March 31, 2018 3,517 $ 35.70

BENEFIT PLANS (Tables)

BENEFIT PLANS (Tables)	3 Months Ended
	Mar. 31, 2018
Defined Benefit Plans and Other Postretirement Benefit Plans Disclosures [Abstract]
Schedule of Net Benefit Costs	Pension and other postretirement benefit expenses are included in acquisition and operating expenses in the consolidated statement of earnings, which includes $5 million of other components of net periodic pension cost and postretirement costs (other than service costs) for the three months ended March 31, 2018 and 2017, respectively. Total net periodic cost includes the following components: Three Months Ended March 31, Pension Benefits Other Japan U.S. Postretirement Benefits (In millions) 2018 2017 2018 2017 2018 2017 Components of net periodic Service cost $ 5 $ 5 $ 7 $ 6 $ 0 $ 0 Interest cost 2 1 9 8 0 0 Expected return on plan (2 ) (1 ) (7 ) (6 ) 0 0 Amortization of net actuarial 0 0 4 3 0 0 Amortization of prior service 0 0 0 0 0 0 Net periodic (benefit) cost $ 5 $ 5 $ 13 $ 11 $ 0 $ 0

Summary of Significant Accoun33

Summary of Significant Accounting Policies - Additional Information (Detail) $ in Millions		Feb. 13, 2018	Mar. 31, 2018USD ($)	Mar. 31, 2017USD ($)	Dec. 31, 2017
Significant Accounting Policies [Line Items]
Stock Split, Conversion Ratio		2
Common stock as a percentage of two-for-one stock split dividend		100.00%
Aflac Japan
Significant Accounting Policies [Line Items]
Percentage of the Company's total assets			85.00%		83.00%
Percentage of the Company's total revenues			71.00%	69.00%
Upper Limit | Accounting Standards Update 2016-02
Significant Accounting Policies [Line Items]
Estimation of Percent of Leases Within Scope of the Guidance to Total Assets			1.00%
Accumulated other comprehensive income (loss): | Accounting Standards Update 2016-01
Significant Accounting Policies [Line Items]
Cumulative effect of change in accounting principle, net of income taxes	[1]		$ (148)	$ 0
Accumulated other comprehensive income (loss): | Accounting Standards Update 2018-02
Significant Accounting Policies [Line Items]
Cumulative effect of change in accounting principle, net of income taxes	[1]		374	0
Retained earnings | Accounting Standards Update 2016-01
Significant Accounting Policies [Line Items]
Cumulative effect of change in accounting principle, net of income taxes	[1]		148	0
Retained earnings | Accounting Standards Update 2018-02
Significant Accounting Policies [Line Items]
Cumulative effect of change in accounting principle, net of income taxes	[1]		$ (374)	$ 0
[1]	See Note 1 of the Notes to the Consolidated Financial Statements for the adoption of accounting guidance on January 1, 2018.

BUSINESS SEGMENT INFORMATION -

BUSINESS SEGMENT INFORMATION - Operations by Segment - Revenues (Details) $ in Millions		3 Months Ended
		Mar. 31, 2018USD ($)segment	Mar. 31, 2017USD ($)
Segment Reporting, Revenue Reconciling Item [Line Items]
Number of Reportable Insurance Business Segments | segment		2
Net earned premiums		$ 4,745	$ 4,638
Net investment income		837	794
Total adjusted revenues		5,546	5,397
Realized investment gains (losses)	[1],[2]	(82)	(88)
Total revenues		5,464	5,309
Gain (loss) on change in fair value of derivative, corporate		2
Aflac Japan
Segment Reporting, Revenue Reconciling Item [Line Items]
Net earned premiums		3,263	3,194
Net investment income, less amortized hedge costs	[2]	588	557
Other income (loss)		12	10
Total revenues		3,863	3,761
Hedge costs		55	52
Aflac U.S.
Segment Reporting, Revenue Reconciling Item [Line Items]
Net earned premiums		1,427	1,390
Net investment income		175	178
Other income (loss)		2	1
Total revenues		1,604	1,569
Corporate and other
Segment Reporting, Revenue Reconciling Item [Line Items]
Total revenues	[1]	$ 79	$ 67
[1]	Amortized hedge costs in Aflac Japan were offset by derivatives entered into as part of corporate activities and resulted in a benefit of $2 for the three-month period ended March 31, 2018 which has been reclassified from realized investment gains (losses) and reported as an increase in net investment income when analyzing operations.
[2]	Amortized hedge costs related to hedging U.S. dollar-denominated investments held in Aflac Japan were $55 and $52 for the three-month periods ended March 31, 2018, and 2017, respectively, and have been reclassified from realized investment gains (losses) and reported as a deduction from net investment income when analyzing segment operations.

BUSINESS SEGMENT INFORMATION 35

BUSINESS SEGMENT INFORMATION - Operations by Segment - Pretax Earnings (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2018	Mar. 31, 2017
Segment Reporting, Reconciling Item for Adjusted Profit (Loss) from Segment to Consolidated [Line Items]
Pretax adjusted earnings		$ 1,109	$ 1,027
Realized investment gains (losses)	[1],[2],[3]	(98)	(109)
Other income (loss)		(29)	(20)
Earnings before income taxes		982	898
Income taxes applicable to pretax adjusted earnings		289	351
Effect of foreign currency translation on after tax adjusted earnings		21	5
Gain (loss) on change in fair value of derivative, corporate		2
Gain (loss) on change in fair value of derivative, interest rate component		17	21
Aflac Japan
Segment Reporting, Reconciling Item for Adjusted Profit (Loss) from Segment to Consolidated [Line Items]
Pretax adjusted earnings	[2]	818	769
Hedge costs		55	52
Aflac U.S.
Segment Reporting, Reconciling Item for Adjusted Profit (Loss) from Segment to Consolidated [Line Items]
Pretax adjusted earnings		337	310
Corporate and other
Segment Reporting, Reconciling Item for Adjusted Profit (Loss) from Segment to Consolidated [Line Items]
Pretax adjusted earnings	[1]	$ (46)	$ (52)
[1]	Amortized hedge costs in Aflac Japan were offset by derivatives entered into as part of corporate activities and resulted in a benefit of $2 for the three-month period ended March 31, 2018 which has been reclassified from realized investment gains (losses) and reported as an increase in pretax adjusted earnings when analyzing operations.
[2]	Amortized hedge costs related to hedging U.S. dollar-denominated investments held in Aflac Japan were $55 and $52 for the three-month periods ended March 31, 2018, and 2017, respectively, and have been reclassified from realized investment gains (losses) and reported as a deduction from pretax adjusted earnings when analyzing segment operations.
[3]	Excluding a gain of $17 and $21 for the three-month periods ended March 31, 2018, and 2017, respectively, related to the interest rate component of the change in fair value of foreign currency swaps on notes payable which is included in adjusted earnings when analyzing segment operations

BUSINESS SEGMENT INFORMATION 36

BUSINESS SEGMENT INFORMATION - Operations by Segment - Assets (Detail) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	$ 147,356	$ 137,217
Aflac Japan
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	125,174	114,402
Aflac U.S.
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	19,706	19,893
Corporate and other
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	$ 2,476	$ 2,922

INVESTMENTS - Schedule of Avail

INVESTMENTS - Schedule of Available-for-sale Securities (Details) - USD ($) $ in Millions		Mar. 31, 2018		Dec. 31, 2017
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost		$ 81,607	[1]	$ 75,132	[2]
Gross Unrealized Gains		8,998		9,985
Gross Unrealized Losses		1,572		804
Fair Value	[3]	89,033	[1]	84,313	[2]
Equity securities
Schedule of Available-for-sale Securities [Line Items]
Fair Value				1,023
Perpetual Securities, Fair Value		71
Fixed maturities
Schedule of Available-for-sale Securities [Line Items]
Fair Value	[3]	89,033		84,313
Perpetual Securities, Amortized Cost		1,506		1,462
Perpetual Securities, Fair Value		1,774		1,789
Yen-denominated | Equity securities
Schedule of Available-for-sale Securities [Line Items]
Fair Value				695
Yen-denominated | Fixed maturities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost		46,154		40,378
Gross Unrealized Gains		5,964		5,582
Gross Unrealized Losses		318		350
Fair Value		51,800		45,610
Dollar-denominated | Equity securities
Schedule of Available-for-sale Securities [Line Items]
Fair Value				328
Dollar-denominated | Fixed maturities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost		35,453		34,754
Gross Unrealized Gains		3,034		4,403
Gross Unrealized Losses		1,254		454
Fair Value		37,233		38,703
Japan government and agencies | Yen-denominated | Fixed maturities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost		32,961		27,980
Gross Unrealized Gains		3,811		3,363
Gross Unrealized Losses		192		271
Fair Value		36,580		31,072
Municipalities | Fixed maturities
Schedule of Available-for-sale Securities [Line Items]
Fair Value		1,373		1,370
Municipalities | Yen-denominated | Fixed maturities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost		350		314
Gross Unrealized Gains		33		28
Gross Unrealized Losses		11		12
Fair Value		372		330
Municipalities | Dollar-denominated | Fixed maturities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost		866		872
Gross Unrealized Gains		135		168
Gross Unrealized Losses		0		0
Fair Value		1,001		1,040
Mortgage- and asset-backed securities | Fixed maturities
Schedule of Available-for-sale Securities [Line Items]
Fair Value		455		444
Mortgage- and asset-backed securities | Yen-denominated | Fixed maturities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost		254		242
Gross Unrealized Gains		30		29
Gross Unrealized Losses		0		0
Fair Value		284		271
Mortgage- and asset-backed securities | Dollar-denominated | Fixed maturities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost		165		161
Gross Unrealized Gains		7		12
Gross Unrealized Losses		1		0
Fair Value		171		173
Public utilities | Fixed maturities
Schedule of Available-for-sale Securities [Line Items]
Fair Value		7,807		7,954
Public utilities | Yen-denominated | Fixed maturities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost		1,739		1,635
Gross Unrealized Gains		325		352
Gross Unrealized Losses		4		6
Fair Value		2,060		1,981
Public utilities | Dollar-denominated | Fixed maturities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost		5,223		5,116
Gross Unrealized Gains		631		884
Gross Unrealized Losses		107		27
Fair Value		5,747		5,973
Sovereign and supranational | Fixed maturities
Schedule of Available-for-sale Securities [Line Items]
Fair Value		1,866		1,909
Sovereign and supranational | Yen-denominated | Fixed maturities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost		1,348		1,380
Gross Unrealized Gains		212		190
Gross Unrealized Losses		27		1
Fair Value		1,533		1,569
Sovereign and supranational | Dollar-denominated | Fixed maturities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost		274		267
Gross Unrealized Gains		59		73
Gross Unrealized Losses		0		0
Fair Value		333		340
Banks/financial institutions | Fixed maturities
Schedule of Available-for-sale Securities [Line Items]
Fair Value		9,144		8,933
Banks/financial institutions | Yen-denominated | Fixed maturities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost		5,157		4,742
Gross Unrealized Gains		799		811
Gross Unrealized Losses		76		53
Fair Value		5,880		5,500
Banks/financial institutions | Dollar-denominated | Fixed maturities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost		2,841		2,808
Gross Unrealized Gains		457		633
Gross Unrealized Losses		34		8
Fair Value		3,264		3,433
Other corporate | Fixed maturities
Schedule of Available-for-sale Securities [Line Items]
Fair Value		31,652		32,473
Other corporate | Yen-denominated | Fixed maturities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost		4,345		4,085
Gross Unrealized Gains		754		809
Gross Unrealized Losses		8		7
Fair Value		5,091		4,887
Other corporate | Dollar-denominated | Fixed maturities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost		25,936		25,384
Gross Unrealized Gains		1,736		2,620
Gross Unrealized Losses		1,111		418
Fair Value		26,561		27,586
U.S. government and agencies | Dollar-denominated | Fixed maturities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost		148		146
Gross Unrealized Gains		9		13
Gross Unrealized Losses		1		1
Fair Value		$ 156		$ 158
[1]	Includes perpetual securities ($1,506 at amortized cost and $1,774 at fair value)
[2]	Includes perpetual securities ($1,462 at amortized cost and $1,789 at fair value)
[3]	Includes perpetual securities

INVESTMENTS - Held-to-Maturity

INVESTMENTS - Held-to-Maturity Investments in Debt Securities (Details) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Schedule of Held-to-maturity Securities [Line Items]
Securities held to maturity, fixed maturities, amortized cost	$ 33,377	$ 31,430
Gross Unrealized Gains	7,104	6,651
Gross Unrealized Losses	13	9
Fair Value	40,468	38,072
Fixed maturities
Schedule of Held-to-maturity Securities [Line Items]
Fair Value	40,468	38,072
Yen-denominated | Fixed maturities
Schedule of Held-to-maturity Securities [Line Items]
Securities held to maturity, fixed maturities, amortized cost	33,377	31,430
Gross Unrealized Gains	7,104	6,651
Gross Unrealized Losses	13	9
Fair Value	40,468	38,072
Japan government and agencies | Yen-denominated | Fixed maturities
Schedule of Held-to-maturity Securities [Line Items]
Securities held to maturity, fixed maturities, amortized cost	22,686	21,331
Gross Unrealized Gains	5,631	5,160
Gross Unrealized Losses	0	0
Fair Value	28,317	26,491
Municipalities | Fixed maturities
Schedule of Held-to-maturity Securities [Line Items]
Securities held to maturity, fixed maturities, amortized cost	379	357
Fair Value	493	462
Municipalities | Yen-denominated | Fixed maturities
Schedule of Held-to-maturity Securities [Line Items]
Securities held to maturity, fixed maturities, amortized cost	379	357
Gross Unrealized Gains	114	105
Gross Unrealized Losses	0	0
Fair Value	493	462
Mortgage- and asset-backed securities | Fixed maturities
Schedule of Held-to-maturity Securities [Line Items]
Securities held to maturity, fixed maturities, amortized cost	26	26
Fair Value	28	27
Mortgage- and asset-backed securities | Yen-denominated | Fixed maturities
Schedule of Held-to-maturity Securities [Line Items]
Securities held to maturity, fixed maturities, amortized cost	26	26
Gross Unrealized Gains	2	1
Gross Unrealized Losses	0	0
Fair Value	28	27
Public utilities | Fixed maturities
Schedule of Held-to-maturity Securities [Line Items]
Securities held to maturity, fixed maturities, amortized cost	3,508	3,300
Fair Value	3,891	3,698
Public utilities | Yen-denominated | Fixed maturities
Schedule of Held-to-maturity Securities [Line Items]
Securities held to maturity, fixed maturities, amortized cost	3,508	3,300
Gross Unrealized Gains	383	398
Gross Unrealized Losses	0	0
Fair Value	3,891	3,698
Sovereign and supranational | Fixed maturities
Schedule of Held-to-maturity Securities [Line Items]
Securities held to maturity, fixed maturities, amortized cost	1,620	1,523
Fair Value	1,919	1,835
Sovereign and supranational | Yen-denominated | Fixed maturities
Schedule of Held-to-maturity Securities [Line Items]
Securities held to maturity, fixed maturities, amortized cost	1,620	1,523
Gross Unrealized Gains	299	312
Gross Unrealized Losses	0	0
Fair Value	1,919	1,835
Banks/financial institutions | Fixed maturities
Schedule of Held-to-maturity Securities [Line Items]
Securities held to maturity, fixed maturities, amortized cost	2,300	2,206
Fair Value	2,477	2,387
Banks/financial institutions | Yen-denominated | Fixed maturities
Schedule of Held-to-maturity Securities [Line Items]
Securities held to maturity, fixed maturities, amortized cost	2,300	2,206
Gross Unrealized Gains	190	190
Gross Unrealized Losses	13	9
Fair Value	2,477	2,387
Other corporate | Fixed maturities
Schedule of Held-to-maturity Securities [Line Items]
Securities held to maturity, fixed maturities, amortized cost	2,858	2,687
Fair Value	3,343	3,172
Other corporate | Yen-denominated | Fixed maturities
Schedule of Held-to-maturity Securities [Line Items]
Securities held to maturity, fixed maturities, amortized cost	2,858	2,687
Gross Unrealized Gains	485	485
Gross Unrealized Losses	0	0
Fair Value	$ 3,343	$ 3,172

INVESTMENTS - Equity Securities

INVESTMENTS - Equity Securities, FV-NI (Details) $ in Millions	Mar. 31, 2018USD ($)
Equity Securities, FV-NI [Line Items]
Fair Value	$ 1,108	[1],[2]
Yen-denominated
Equity Securities, FV-NI [Line Items]
Fair Value	711
Dollar-denominated
Equity Securities, FV-NI [Line Items]
Fair Value	397
Equity securities
Equity Securities, FV-NI [Line Items]
Perpetual Securities, Fair Value	$ 71
[1]	Includes perpetual securities
[2]	Includes perpetual securities ($71 at fair value)

INVESTMENTS - Additional Inform

INVESTMENTS - Additional Information (Detail) $ in Millions	3 Months Ended
	Mar. 31, 2018USD ($)investment	Mar. 31, 2017investment	Dec. 31, 2017USD ($)
Schedule of Investments [Line Items]
Equity securities, FV-NI, unrealized gain (loss)	$ (43)
Held to maturity securities transferred to available for sale securities, number of investments | investment	0	0
Middle market loan program unfunded amount	$ 76		$ 109
Middle market loan commitments	$ 985
Percentage that the lending policy requires that the fair value of the securities and/or unrestricted cash received as collateral be of the fair value of the loaned securities	102.00%
Allowance for loan loss	$ 18		$ 11
Transitional real estate loan commitments	436
Commercial mortgage loan commitments	54
Limited partnerships investment commitments	$ 763

INVESTMENTS - Contractual and E

INVESTMENTS - Contractual and Economic Maturities of Investments in Fixed Maturities (Detail) - USD ($) $ in Millions		Mar. 31, 2018	Dec. 31, 2017
Available for sale:
Due in one year or less	[1]	$ 485
Due after one year through five years	[1]	9,685
Due after five years through 10 years	[1]	10,637
Due after 10 years	[1]	60,381
Mortgage- and asset-backed securities	[1]	419
Total fixed maturity securities, available for sale, amortized cost	[1]	81,607
Held to maturity:
Due in one year or less		1,036
Due after one year through five years		508
Due after five years through 10 years		1,597
Due after 10 years		30,210
Mortgage- and asset-backed securities		26
Total fixed maturity securities, held to maturity, amortized cost		33,377	$ 31,430
Available for sale:
Due in one year or less	[1]	502
Due after one year through five years	[1]	9,551
Due after five years through 10 years	[1]	11,143
Due after 10 years	[1]	67,382
Mortgage- and asset-backed securities	[1]	455
Total fixed maturity securities, available for sale, fair value	[1]	89,033
Held to maturity:
Due in one year or less		1,049
Due after one year through five years		527
Due after five years through 10 years		1,754
Due after 10 years		37,110
Mortgage- and asset-backed securities		28
Total fixed maturity securities, held to maturity, fair value		$ 40,468	$ 38,072
[1]	Includes perpetual securities, categorized in accordance with their respective economic maturities (the expected maturity date created by the combination of features in the financial instrument)

INVESTMENTS - Investment Exposu

INVESTMENTS - Investment Exposures Individually Exceeded 10% of Shareholders' Equity (Details) - Japan National Government - USD ($) $ in Millions		3 Months Ended	12 Months Ended
		Mar. 31, 2018	Dec. 31, 2017
Summary of Investment Holdings [Line Items]
Credit Rating	[1]	A	A
Amortized Cost	[1]	$ 54,465	$ 48,399
Fair Value	[1]	$ 63,576	$ 56,532
[1]	Japan Government Bonds (JGBs) or JGB-backed securities

INVESTMENTS - Information Regar

INVESTMENTS - Information Regarding Pretax Realized Gains and Losses From Investments (Detail) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2018	Mar. 31, 2017
Gain (Loss) on Investments [Line Items]
Other-than-temporary impairment losses realized		$ (7)	$ (10)
Loan loss reserves		(7)	(1)
Derivative gains (losses)		144	(52)
Foreign currency gains (losses)		(228)	(71)
Total realized investment gains (losses)		(134)	(140)
Derivatives and other
Gain (Loss) on Investments [Line Items]
Total realized investment gains (losses)		(84)	(123)
Equity securities
Gain (Loss) on Investments [Line Items]
Other-than-temporary impairment losses realized			(6)
Total realized investment gains (losses)	[1],[2]	(46)	19
Available-for-sale securities | Fixed maturities
Gain (Loss) on Investments [Line Items]
Gross gains from sales	[3]	9	12
Gross losses from sales	[3]	(4)	(15)
Net gains (losses) from redemptions	[3]	(2)	(28)
Other-than-temporary impairment losses realized	[3]	0	(4)
Total realized investment gains (losses)	[3]	$ 3	$ (35)
[1]	Includes $6 of impairments
[2]	See Note 1 of the Notes to the Consolidated Financial Statements for the adoption of accounting guidance on January 1, 2018 related to financial instruments.
[3]	Includes perpetual securities

INVESTMENTS - Net Effect on Sha

INVESTMENTS - Net Effect on Shareholders' Equity of Unrealized Gains and Losses from Investment Securities (Detail) - USD ($) $ in Millions		3 Months Ended	12 Months Ended
		Mar. 31, 2018	Dec. 31, 2017
Investments [Abstract]
Unrealized Gains (Losses) on Available-for-sale Securities	[1]	$ 7,426	$ 9,358
Deferred income taxes	[1]	(2,220)	(3,394)
Shareholders' equity, unrealized gains (losses) on investment securities	[1],[2]	$ 5,206	$ 5,964
[1]	See Note 1 for discussion of the accounting treatment of tax on amounts recorded in accumulated other comprehensive income pursuant to the Tax Act and for the adoption of accounting guidance on January 1, 2018 related to financial instruments.
[2]	See Note 1 of the Notes to the Consolidated Financial Statements for the adoption of accounting guidance on January 1, 2018 related to financial instruments.

INVESTMENTS - Fair Value and Gr

INVESTMENTS - Fair Value and Gross Unrealized Losses for Securities That Have Been in Continuous Unrealized Loss Position (Detail) - USD ($) $ in Millions		3 Months Ended	12 Months Ended
		Mar. 31, 2018	Dec. 31, 2017
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	[1]	$ 22,577	$ 16,685
Total Unrealized Losses	[1]	1,585	813
Less than 12 months Fair Value	[1]	12,087	5,776
Less than 12 months Unrealized Losses	[1]	549	77
12 months or longer Fair Value	[1]	10,490	10,909
12 months or longer Unrealized Losses	[1]	1,036	736
Dollar-denominated | Fixed maturities | U.S. government and agencies
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	[1]	79	74
Total Unrealized Losses	[1]	1	1
Less than 12 months Fair Value	[1]	71	74
Less than 12 months Unrealized Losses	[1]	1	1
12 months or longer Fair Value	[1]	8	0
12 months or longer Unrealized Losses	[1]	0	0
Dollar-denominated | Fixed maturities | Mortgage- and asset-backed securities
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	[1]	91
Total Unrealized Losses	[1]	1
Less than 12 months Fair Value	[1]	71
Less than 12 months Unrealized Losses	[1]	1
12 months or longer Fair Value	[1]	20
12 months or longer Unrealized Losses	[1]	0
Dollar-denominated | Fixed maturities | Public utilities
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	[1]	1,649	785
Total Unrealized Losses	[1]	107	27
Less than 12 months Fair Value	[1]	1,095	221
Less than 12 months Unrealized Losses	[1]	52	3
12 months or longer Fair Value	[1]	554	564
12 months or longer Unrealized Losses	[1]	55	24
Dollar-denominated | Fixed maturities | Banks/financial institutions
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	[1]	685	362
Total Unrealized Losses	[1]	34	8
Less than 12 months Fair Value	[1]	596	316
Less than 12 months Unrealized Losses	[1]	28	5
12 months or longer Fair Value	[1]	89	46
12 months or longer Unrealized Losses	[1]	6	3
Dollar-denominated | Fixed maturities | Other corporate
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	[1]	13,730	7,741
Total Unrealized Losses	[1]	1,111	418
Less than 12 months Fair Value	[1]	8,903	2,839
Less than 12 months Unrealized Losses	[1]	420	50
12 months or longer Fair Value	[1]	4,827	4,902
12 months or longer Unrealized Losses	[1]	691	368
Yen-denominated | Fixed maturities | Japan government and agencies
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	[1]	4,054	5,255
Total Unrealized Losses	[1]	192	271
Less than 12 months Fair Value	[1]	128	1,264
Less than 12 months Unrealized Losses	[1]	0	9
12 months or longer Fair Value	[1]	3,926	3,991
12 months or longer Unrealized Losses	[1]	192	262
Yen-denominated | Fixed maturities | Municipalities
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	[1]	128	129
Total Unrealized Losses	[1]	11	12
Less than 12 months Fair Value	[1]	0	10
Less than 12 months Unrealized Losses	[1]	0	0
12 months or longer Fair Value	[1]	128	119
12 months or longer Unrealized Losses	[1]	11	12
Yen-denominated | Fixed maturities | Public utilities
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	[1]	90	83
Total Unrealized Losses	[1]	4	6
Less than 12 months Fair Value	[1]	0	0
Less than 12 months Unrealized Losses	[1]	0	0
12 months or longer Fair Value	[1]	90	83
12 months or longer Unrealized Losses	[1]	4	6
Yen-denominated | Fixed maturities | Sovereign and supranational
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	[1]	302	309
Total Unrealized Losses	[1]	27	1
Less than 12 months Fair Value	[1]	302	309
Less than 12 months Unrealized Losses	[1]	27	1
12 months or longer Fair Value	[1]	0	0
12 months or longer Unrealized Losses	[1]	0	0
Yen-denominated | Fixed maturities | Banks/financial institutions
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	[1]	1,467	1,507
Total Unrealized Losses	[1]	89	62
Less than 12 months Fair Value	[1]	645	394
Less than 12 months Unrealized Losses	[1]	14	4
12 months or longer Fair Value	[1]	822	1,113
12 months or longer Unrealized Losses	[1]	75	58
Yen-denominated | Fixed maturities | Other corporate
Investments, Unrealized Loss Position [Line Items]
Total Fair Value	[1]	302	440
Total Unrealized Losses	[1]	8	7
Less than 12 months Fair Value	[1]	276	349
Less than 12 months Unrealized Losses	[1]	6	4
12 months or longer Fair Value	[1]	26	91
12 months or longer Unrealized Losses	[1]	$ 2	$ 3
[1]	Includes perpetual securities

INVESTMENTS - Other Investments

INVESTMENTS - Other Investments (Details) - USD ($) $ in Millions		Mar. 31, 2018	Dec. 31, 2017
Investment Holdings [Line Items]
Other investments	[1]	$ 5,073	$ 3,402
Transitional real estate loans
Investment Holdings [Line Items]
Other investments		2,719	1,235
Commercial mortgage loans
Investment Holdings [Line Items]
Other investments		917	908
Middle market loans
Investment Holdings [Line Items]
Other investments		957	859
Policy loans
Investment Holdings [Line Items]
Other investments		227	210
Short-term investments
Investment Holdings [Line Items]
Other investments		0	57
Other investments
Investment Holdings [Line Items]
Other investments		$ 253	$ 133
[1]	Includes $3,994 in 2018 and $2,341 in 2017 of loan receivables and limited partnerships from consolidated variable interest entities

INVESTMENTS - Investments in Co

INVESTMENTS - Investments in Consolidated Variable Interest Entities (Detail) - USD ($) $ in Millions		Mar. 31, 2018	Dec. 31, 2017
Variable Interest Entity [Line Items]
Securities available for sale, fixed maturities, amortized cost	[1]	$ 81,607
Securities available for sale, fixed maturities, fair value	[1]	89,033
Equity securities	[2],[3]	1,108
Other investments	[4]	5,073	$ 3,402
Asset derivatives		797	331
Assets, fair value		95,018	89,215
Liability derivatives		353	474
Liabilities		123,069	112,619
Liabilities, fair value disclosure		353	474
Variable Interest Entity, Consolidated
Variable Interest Entity [Line Items]
Securities available for sale, fixed maturities, amortized cost	[5],[6]	4,695	4,538
Securities available for sale, fixed maturities, fair value	[5],[6]	5,431	5,509
Available-for-sale equity securities, amortized cost basis			606
Equity securities, FV-NI, cost		760
Equity securities		760
Available-for-sale securities, equity securities			753
Other investments	[7]	3,994	2,341
Other investments, fair value	[7]	3,974	2,328
Asset derivatives, amortized cost	[8]	241	151
Asset derivatives	[8]	241	151
Assets, amortized cost		9,690	7,636
Assets, fair value		10,406	8,741
Liability derivatives, amortized cost	[8]	86	128
Liability derivatives	[8]	86	128
Liabilities		86	128
Liabilities, fair value disclosure		$ 86	$ 128
[1]	Includes perpetual securities, categorized in accordance with their respective economic maturities (the expected maturity date created by the combination of features in the financial instrument)
[2]	Includes perpetual securities
[3]	Includes perpetual securities ($71 at fair value)
[4]	Includes $3,994 in 2018 and $2,341 in 2017 of loan receivables and limited partnerships from consolidated variable interest entities
[5]	Includes perpetual securities
[6]	Includes perpetual securities, see Notes 1 and 3 of the Notes to the Consolidated Financial Statements
[7]	Consists of TREs, CMLs, MMLs, and alternative investments in limited partnerships
[8]	Consists entirely of derivatives

INVESTMENTS - Investments in Va

INVESTMENTS - Investments in Variable Interest Entities Not Consolidated (Details) - USD ($) $ in Millions		Mar. 31, 2018	Dec. 31, 2017
Variable Interest Entity [Line Items]
Securities available for sale, fixed maturities, amortized cost	[1]	$ 81,607
Securities available for sale, fixed maturities, fair value	[1]	89,033
Securities held to maturity, fixed maturities, amortized cost		33,377	$ 31,430
Securities held to maturity, fixed maturities, fair value		40,468	38,072
Other investments	[2]	5,073	3,402
Assets, fair value		95,018	89,215
Variable Interest Entity, Not Consolidated
Variable Interest Entity [Line Items]
Securities available for sale, fixed maturities, amortized cost	[3]	5,194	5,004
Securities available for sale, fixed maturities, fair value	[3]	5,749	5,724
Securities held to maturity, fixed maturities, amortized cost		2,711	2,549
Securities held to maturity, fixed maturities, fair value		3,077	2,929
Other investments		110	55
Other investments, fair value		108	55
Assets, amortized cost		8,015	7,608
Assets, fair value		$ 8,934	$ 8,708
[1]	Includes perpetual securities, categorized in accordance with their respective economic maturities (the expected maturity date created by the combination of features in the financial instrument)
[2]	Includes $3,994 in 2018 and $2,341 in 2017 of loan receivables and limited partnerships from consolidated variable interest entities
[3]	Includes perpetual securities

INVESTMENTS - Securities Lendin

INVESTMENTS - Securities Lending Transactions Accounted for as Secured Borrowings (Details) - USD ($) $ in Millions		Mar. 31, 2018	Dec. 31, 2017
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities Loaned, Including Not Subject to Master Netting Arrangement and Assets other than Securities Transferred		$ 5,368	$ 606
Gross amount of recognized liabilities for securities lending		5,368	606
Amounts related to agreements not included in offsetting disclosure in Note 4		0	0
Japan government and agencies
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities Loaned, Including Not Subject to Master Netting Arrangement and Assets other than Securities Transferred		4,894	49
Public utilities
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities Loaned, Including Not Subject to Master Netting Arrangement and Assets other than Securities Transferred		30	73
Banks/financial institutions
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities Loaned, Including Not Subject to Master Netting Arrangement and Assets other than Securities Transferred		52	54
Other corporate
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities Loaned, Including Not Subject to Master Netting Arrangement and Assets other than Securities Transferred		384	415
Equity securities
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities Loaned, Including Not Subject to Master Netting Arrangement and Assets other than Securities Transferred		8	15
Maturity Overnight and Continuous
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities Loaned, Including Not Subject to Master Netting Arrangement and Assets other than Securities Transferred	[1]	474	557
Maturity Overnight and Continuous | Japan government and agencies
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities Loaned, Including Not Subject to Master Netting Arrangement and Assets other than Securities Transferred	[1]	0	0
Maturity Overnight and Continuous | Public utilities
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities Loaned, Including Not Subject to Master Netting Arrangement and Assets other than Securities Transferred	[1]	30	73
Maturity Overnight and Continuous | Banks/financial institutions
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities Loaned, Including Not Subject to Master Netting Arrangement and Assets other than Securities Transferred	[1]	52	54
Maturity Overnight and Continuous | Other corporate
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities Loaned, Including Not Subject to Master Netting Arrangement and Assets other than Securities Transferred	[1]	384	415
Maturity Overnight and Continuous | Equity securities
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities Loaned, Including Not Subject to Master Netting Arrangement and Assets other than Securities Transferred	[1]	8	15
Maturity up to 30 Days
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities Loaned, Including Not Subject to Master Netting Arrangement and Assets other than Securities Transferred		4,894	49
Maturity up to 30 Days | Japan government and agencies
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities Loaned, Including Not Subject to Master Netting Arrangement and Assets other than Securities Transferred		4,894	49
Maturity up to 30 Days | Public utilities
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities Loaned, Including Not Subject to Master Netting Arrangement and Assets other than Securities Transferred		0	0
Maturity up to 30 Days | Banks/financial institutions
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities Loaned, Including Not Subject to Master Netting Arrangement and Assets other than Securities Transferred		0	0
Maturity up to 30 Days | Other corporate
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities Loaned, Including Not Subject to Master Netting Arrangement and Assets other than Securities Transferred		0	0
Maturity up to 30 Days | Equity securities
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities Loaned, Including Not Subject to Master Netting Arrangement and Assets other than Securities Transferred		$ 0	$ 0
[1]	These securities are pledged as collateral under the Company's U.S. securities lending program and can be called at its discretion; therefore, they are classified as Overnight and Continuous.

DERIVATIVE INSTRUMENTS - Additi

DERIVATIVE INSTRUMENTS - Additional Information (Detail) $ in Millions	3 Months Ended
	Mar. 31, 2018USD ($)yrcounterparties	Mar. 31, 2017USD ($)	Dec. 31, 2017USD ($)
Derivative Instruments and Hedging Activities Disclosure [Line Items]
Cash flow hedging activity, maximum time period | yr	9
Number of counterparties | counterparties	15
Number of counterparties that comprise majority of aggregate notional amount of swaps | counterparties	4
Percentage of notional amount of swaps from certain number of counterparties	59.00%
Derivative, Net Liability Position, Aggregate Fair Value	$ 154		$ 264
Additional Collateral, Aggregate Fair Value	5
Net investment hedge
Derivative Instruments and Hedging Activities Disclosure [Line Items]
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	0	$ 0
2.40% senior notes due March 2020
Derivative Instruments and Hedging Activities Disclosure [Line Items]
Debt instrument, principal amount	550
4.00% senior notes due February 2022
Derivative Instruments and Hedging Activities Disclosure [Line Items]
Debt instrument, principal amount	350
3.625% senior notes due June 2023
Derivative Instruments and Hedging Activities Disclosure [Line Items]
Debt instrument, principal amount	700
3.625% senior notes due November 2024
Derivative Instruments and Hedging Activities Disclosure [Line Items]
Debt instrument, principal amount	750
3.25% senior notes due March 2025
Derivative Instruments and Hedging Activities Disclosure [Line Items]
Debt instrument, principal amount	$ 450

DERIVATIVE INSTRUMENTS - Summar

DERIVATIVE INSTRUMENTS - Summary of Balance Sheet Classification of Derivative Fair Value Amounts, as well as Gross Asset and Liability Fair Value Amounts (Detail) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Derivatives, Fair Value [Line Items]
Net Derivatives Notional Amount	$ 27,220	$ 25,751
Derivative asset, fair value, gross asset including not subject to master netting arrangement	797	331
Derivative liability, fair value, gross liability including not subject to master netting arrangement	(353)	(474)
Asset derivatives fair value	556	180
Liability derivatives fair value	(267)	(346)
Other assets
Derivatives, Fair Value [Line Items]
Net Derivatives Notional Amount	18,248	10,948
Asset derivatives fair value	797	331
Liability derivatives fair value	0	0
Other liabilities
Derivatives, Fair Value [Line Items]
Net Derivatives Notional Amount	8,972	14,803
Asset derivatives fair value	0	0
Liability derivatives fair value	(353)	(474)
Cash flow hedges
Derivatives, Fair Value [Line Items]
Net Derivatives Notional Amount	75	75
Asset derivatives fair value	1	0
Liability derivatives fair value	(2)	(8)
Cash flow hedges | Foreign currency swaps
Derivatives, Fair Value [Line Items]
Net Derivatives Notional Amount	75	75
Asset derivatives fair value	1	0
Liability derivatives fair value	(2)	(8)
Fair value hedges
Derivatives, Fair Value [Line Items]
Net Derivatives Notional Amount	14,670	15,310
Asset derivatives fair value	244	2
Liability derivatives fair value	(8)	(223)
Fair value hedges | Foreign currency forwards
Derivatives, Fair Value [Line Items]
Net Derivatives Notional Amount	5,550	7,640
Asset derivatives fair value	244	2
Liability derivatives fair value	(5)	(221)
Fair value hedges | Foreign currency options
Derivatives, Fair Value [Line Items]
Net Derivatives Notional Amount	9,120	7,670
Asset derivatives fair value	0	0
Liability derivatives fair value	(3)	(2)
Net investment hedge
Derivatives, Fair Value [Line Items]
Net Derivatives Notional Amount	0	439
Asset derivatives fair value	0	12
Liability derivatives fair value	0	(1)
Net investment hedge | Foreign currency forwards
Derivatives, Fair Value [Line Items]
Net Derivatives Notional Amount	0	5
Asset derivatives fair value	0	0
Liability derivatives fair value	0	0
Net investment hedge | Foreign currency options
Derivatives, Fair Value [Line Items]
Net Derivatives Notional Amount	0	434
Asset derivatives fair value	0	12
Liability derivatives fair value	0	(1)
Non-qualifying strategies
Derivatives, Fair Value [Line Items]
Net Derivatives Notional Amount	12,475	9,927
Asset derivatives fair value	552	317
Liability derivatives fair value	(343)	(242)
Non-qualifying strategies | Foreign currency swaps
Derivatives, Fair Value [Line Items]
Net Derivatives Notional Amount	5,426	5,386
Asset derivatives fair value	369	296
Liability derivatives fair value	(263)	(189)
Non-qualifying strategies | Foreign currency forwards
Derivatives, Fair Value [Line Items]
Net Derivatives Notional Amount	6,656	3,683
Asset derivatives fair value	182	20
Liability derivatives fair value	(80)	(53)
Non-qualifying strategies | Foreign currency options
Derivatives, Fair Value [Line Items]
Net Derivatives Notional Amount	299	770
Asset derivatives fair value	0	0
Liability derivatives fair value	0	0
Non-qualifying strategies | Credit default swaps
Derivatives, Fair Value [Line Items]
Net Derivatives Notional Amount	94	88
Asset derivatives fair value	1	1
Liability derivatives fair value	$ 0	$ 0

DERIVATIVE INSTRUMENTS - Gains

DERIVATIVE INSTRUMENTS - Gains (Losses) Recognized on Fair Value Hedging Relationships (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Fixed-maturity securities and equity securities | Foreign currency forwards
Derivative Instruments, Gain (Loss) [Line Items]
Total gains (losses) recognized for derivatives		$ 341
Gains (losses) on derivatives excluded from effectiveness testing		(48)
Gains (losses) on derivatives included in effectiveness testing		389
Gains (losses) recognized for hedged items		(372)
Ineffectiveness recognized for fair value hedge		17
Fixed maturity securities | Foreign currency forwards
Derivative Instruments, Gain (Loss) [Line Items]
Total gains (losses) recognized for derivatives	$ 414
Gains (losses) on derivatives excluded from effectiveness testing	(39)
Gains (losses) on derivatives included in effectiveness testing	453
Gains (losses) recognized for hedged items	(464)
Ineffectiveness recognized for fair value hedge	(11)
Fixed maturity securities | Foreign currency options
Derivative Instruments, Gain (Loss) [Line Items]
Total gains (losses) recognized for derivatives	(1)	24
Gains (losses) on derivatives excluded from effectiveness testing	(1)	13
Gains (losses) on derivatives included in effectiveness testing	0	11
Gains (losses) recognized for hedged items	0	(10)
Ineffectiveness recognized for fair value hedge	$ 0	$ 1

DERIVATIVE INSTRUMENTS - Deriva

DERIVATIVE INSTRUMENTS - Derivatives and Hedging Instruments Gain (Loss) Summary (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2018	Mar. 31, 2017
Derivative Instruments, Gain (Loss) [Line Items]
Unrealized foreign currency translation gains (losses) during period		$ 824	$ 375
Derivative gains (losses)		144	(52)
Derivative and non-derivative hedging instruments gain (loss) recognized in other comprehensive income effective portion before tax	[1]	(86)	(47)
Cash flow hedges
Derivative Instruments, Gain (Loss) [Line Items]
Net Realized Investment Gains (Losses) Recognized in Income on Derivative (Ineffective Portion)		1	0
Gain (Loss) Recognized in Other Comprehensive Income on Derivative (Effective Portion)	[1]	6	2
Cash flow hedges | Foreign currency swaps
Derivative Instruments, Gain (Loss) [Line Items]
Net Realized Investment Gains (Losses) Recognized in Income on Derivative (Ineffective Portion)		1	0
Gain (Loss) Recognized in Other Comprehensive Income on Derivative (Effective Portion)	[1]	6	2
Fair value hedges
Derivative Instruments, Gain (Loss) [Line Items]
Net Realized Investment Gains (Losses) Recognized in Income on Derivative (Ineffective Portion)		(51)	(17)
Gain (Loss) Recognized in Other Comprehensive Income on Derivative (Effective Portion)	[1]	0	0
Fair value hedges | Foreign currency forwards
Derivative Instruments, Gain (Loss) [Line Items]
Net Realized Investment Gains (Losses) Recognized in Income on Derivative (Ineffective Portion)	[2]	(50)	(31)
Gain (Loss) Recognized in Other Comprehensive Income on Derivative (Effective Portion)	[1],[2]	0	0
Fair value hedges | Foreign currency options
Derivative Instruments, Gain (Loss) [Line Items]
Net Realized Investment Gains (Losses) Recognized in Income on Derivative (Ineffective Portion)	[2]	(1)	14
Gain (Loss) Recognized in Other Comprehensive Income on Derivative (Effective Portion)	[1],[2]	0	0
Net investment hedge
Derivative Instruments, Gain (Loss) [Line Items]
Net Realized Investment Gains (Losses) Recognized in Income on Derivative (Ineffective Portion)		0	0
Unrealized foreign currency translation gains (losses) during period	[1]	(92)	(49)
Net investment hedge | Non-derivative hedging instruments
Derivative Instruments, Gain (Loss) [Line Items]
Net Realized Investment Gains (Losses) Recognized in Income on Derivative (Ineffective Portion)		0	0
Unrealized foreign currency translation gains (losses) during period	[1]	(84)	(17)
Net investment hedge | Foreign currency forwards
Derivative Instruments, Gain (Loss) [Line Items]
Net Realized Investment Gains (Losses) Recognized in Income on Derivative (Ineffective Portion)		0	0
Unrealized foreign currency translation gains (losses) during period	[1]	0	(9)
Net investment hedge | Foreign currency options
Derivative Instruments, Gain (Loss) [Line Items]
Net Realized Investment Gains (Losses) Recognized in Income on Derivative (Ineffective Portion)		0	0
Unrealized foreign currency translation gains (losses) during period	[1]	(8)	(23)
Non-qualifying strategies
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instruments, Gain (Loss) Recognized in Income, Net		194	(35)
Gain (Loss) Recognized in Other Comprehensive Income on Derivative (Effective Portion)	[1]	0	0
Non-qualifying strategies | Foreign currency swaps
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instruments, Gain (Loss) Recognized in Income, Net		14	(8)
Gain (Loss) Recognized in Other Comprehensive Income on Derivative (Effective Portion)	[1]	0	0
Non-qualifying strategies | Foreign currency forwards
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instruments, Gain (Loss) Recognized in Income, Net		179	(27)
Gain (Loss) Recognized in Other Comprehensive Income on Derivative (Effective Portion)	[1]	0	0
Non-qualifying strategies | Foreign currency options
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instruments, Gain (Loss) Recognized in Income, Net		1	0
Gain (Loss) Recognized in Other Comprehensive Income on Derivative (Effective Portion)	[1]	$ 0	$ 0
[1]	Cash flow hedge items are recorded as unrealized gains (losses) on derivatives and net investment hedge items are recorded in the unrealized foreign currency translation gains (losses) line in the consolidated statement of comprehensive income (loss).
[2]	Impact shown net of effect of hedged items (see Fair Value Hedges section of this Note 4 for further detail)

DERIVATIVE INSTRUMENTS - Fair V

DERIVATIVE INSTRUMENTS - Fair Value and Notional Amounts of Derivatives With Counterparty Credit Risk (Details) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Derivative Instruments and Hedging Activities Disclosure [Line Items]
Notional Amount of Derivatives	$ 27,220	$ 25,751
Asset Derivatives Fair Value	797	331
Liability Derivatives Fair Value	(353)	(474)
AA
Derivative Instruments and Hedging Activities Disclosure [Line Items]
Notional Amount of Derivatives	4,685	4,708
Asset Derivatives Fair Value	123	52
Liability Derivatives Fair Value	(12)	(37)
A
Derivative Instruments and Hedging Activities Disclosure [Line Items]
Notional Amount of Derivatives	22,081	20,604
Asset Derivatives Fair Value	673	271
Liability Derivatives Fair Value	(290)	(370)
BBB
Derivative Instruments and Hedging Activities Disclosure [Line Items]
Notional Amount of Derivatives	454	439
Asset Derivatives Fair Value	1	8
Liability Derivatives Fair Value	$ (51)	$ (67)

DERIVATIVE INSTRUMENTS - Offset

DERIVATIVE INSTRUMENTS - Offsetting of Financial Assets and Derivative Assets (Details) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Offsetting Assets [Line Items]
Gross amount of recognized derivative assets	$ 556	$ 180
Gross amount of liabilities offset in balance sheet	0	0
Net amount of derivative assets presented in the balance sheet	556	180
Financial instruments, amount not offset	(116)	(82)
Derivative, collateral, obligation to return securities	(343)	0
Derivative, collateral, obligation to return cash	(67)	(98)
Derivative asset, fair value, amount offset against collateral, subject to master netting agreement	30	0
Derivative asset, not subject to master netting arrangement	241	151
Derivative asset, fair value, amount offset against collateral, not subject to master netting agreement	241	151
Derivative asset, fair value, gross asset including not subject to master netting arrangement	797	331
Net amount of derivative assets presented in balance sheet	797	331
Derivative asset, fair value, amount offset against collateral	271	151
Gross amounts of recognized financial instruments	6,046	923
Gross amounts offset in balance sheet	0	0
Net amounts of assets presented in balance sheet	6,046	923
Carrying value of financial instruments not offset in balance sheet	(116)	(82)
Securities collateral, not offset in balance sheet	(343)	0
Cash collateral, not offset in balance sheet	(5,316)	(690)
Financial instruments, amount of assets offset against collateral	271	151
Securities lending and similar arrangements
Offsetting Assets [Line Items]
Gross amounts of recognized financial instruments	5,249	592
Gross amounts offset in balance sheet	0	0
Net amounts of assets presented in balance sheet	5,249	592
Carrying value of financial instruments not offset in balance sheet	0	0
Securities collateral, not offset in balance sheet	0	0
Cash collateral, not offset in balance sheet	(5,249)	(592)
Financial instruments, amount of assets offset against collateral	$ 0	$ 0

DERIVATIVE INSTRUMENTS - Offs56

DERIVATIVE INSTRUMENTS - Offsetting of Financial Liabilities and Derivative Liabilities (Details) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Offsetting Liabilities [Line Items]
Gross amount of recognized derivative liabilities	$ (267)	$ (346)
Gross amount of assets offset in balance sheet	0	0
Derivative liability, fair value, amount not offset against collateral	(267)	(346)
Financial instruments, amount not offset	116	82
Derivative, collateral, right to reclaim securities	36	245
Derivative, collateral, right to reclaim cash	113	10
Derivative liability, fair value, amount offset against collateral, subject to master netting agreement	(2)	(9)
Derivative liability, not subject to master netting arrangement	(86)	(128)
Derivative liability, fair value, amount offset against collateral, not subject to master netting agreement	(86)	(128)
Derivative liability, fair value, gross liability including not subject to master netting arrangement	(353)	(474)
Net amount of derivative liabilities presented in balance sheet	(353)	(474)
Derivative liability, fair value, amount offset against collateral	(88)	(137)
Gross Amounts of Recognized Financial Instruments, Offsetting Liabilities	(5,721)	(1,080)
Gross Amounts Offset in Statement of Financial Position, Offsetting Liabilities	0	0
Net Amounts of Financial Instruments Presented in Balance Sheet, Offsetting Liabilities	(5,721)	(1,080)
Carrying value of financial instruments, liabilities not offset in balance sheet	5,365	674
Securities Collateral, Liabilities Not Offset in Balance Sheet	36	245
Cash Collateral, Liabilities Not Offset in Balance Sheet	113	10
Financial instruments, amount of liabilities offset against collateral	(207)	(151)
Securities lending and similar arrangements
Offsetting Liabilities [Line Items]
Gross Amounts of Recognized Financial Instruments, Offsetting Liabilities	(5,368)	(606)
Gross Amounts Offset in Statement of Financial Position, Offsetting Liabilities	0	0
Net Amounts of Financial Instruments Presented in Balance Sheet, Offsetting Liabilities	(5,368)	(606)
Carrying value of financial instruments, liabilities not offset in balance sheet	5,249	592
Securities Collateral, Liabilities Not Offset in Balance Sheet	0	0
Cash Collateral, Liabilities Not Offset in Balance Sheet	0	0
Financial instruments, amount of liabilities offset against collateral	$ (119)	$ (14)

FAIR VALUE MEASUREMENTS - Fair

FAIR VALUE MEASUREMENTS - Fair Value Hierarchy Levels of Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) - USD ($) $ in Millions		Mar. 31, 2018		Dec. 31, 2017
Assets:
Available-for-sale securities	[1]	$ 89,033	[2]	$ 84,313	[3]
Equity securities	[1],[4]	1,108
Asset derivatives		797		331
Other Investments				57
Cash and cash equivalents		4,080		3,491
Total assets		95,018		89,215
Liabilities:
Liability derivatives		353		474
Total liabilities		353		474
Foreign currency swaps
Assets:
Asset derivatives		370		296
Liabilities:
Liability derivatives		265		197
Foreign currency forwards
Assets:
Asset derivatives		426		22
Liabilities:
Liability derivatives		85		274
Foreign currency options
Assets:
Asset derivatives				12
Liabilities:
Liability derivatives		3		3
Credit default swaps
Assets:
Asset derivatives		1		1
Fixed maturities
Assets:
Available-for-sale securities	[1]	89,033		84,313
Fixed maturities | Government and agencies
Assets:
Available-for-sale securities		36,736		31,230
Fixed maturities | Municipalities
Assets:
Available-for-sale securities		1,373		1,370
Fixed maturities | Mortgage- and asset-backed securities
Assets:
Available-for-sale securities		455		444
Fixed maturities | Public utilities
Assets:
Available-for-sale securities		7,807		7,954
Fixed maturities | Sovereign and supranational
Assets:
Available-for-sale securities		1,866		1,909
Fixed maturities | Banks/financial institutions
Assets:
Available-for-sale securities		9,144		8,933
Fixed maturities | Other corporate
Assets:
Available-for-sale securities		31,652		32,473
Equity securities
Assets:
Available-for-sale securities				1,023
Level 1
Assets:
Available-for-sale securities		35,325		30,109
Equity securities		1,015
Asset derivatives		0		0
Other Investments				57
Cash and cash equivalents		4,080		3,491
Total assets		40,420		34,658
Liabilities:
Total liabilities		0		0
Level 1 | Foreign currency swaps
Assets:
Asset derivatives		0		0
Liabilities:
Liability derivatives		0		0
Level 1 | Foreign currency forwards
Assets:
Asset derivatives		0		0
Liabilities:
Liability derivatives		0		0
Level 1 | Foreign currency options
Assets:
Asset derivatives				0
Liabilities:
Liability derivatives		0		0
Level 1 | Credit default swaps
Assets:
Asset derivatives		0		0
Level 1 | Fixed maturities
Assets:
Available-for-sale securities		35,325		30,109
Level 1 | Fixed maturities | Government and agencies
Assets:
Available-for-sale securities		35,325		30,109
Level 1 | Fixed maturities | Municipalities
Assets:
Available-for-sale securities		0		0
Level 1 | Fixed maturities | Mortgage- and asset-backed securities
Assets:
Available-for-sale securities		0		0
Level 1 | Fixed maturities | Public utilities
Assets:
Available-for-sale securities		0		0
Level 1 | Fixed maturities | Sovereign and supranational
Assets:
Available-for-sale securities		0		0
Level 1 | Fixed maturities | Banks/financial institutions
Assets:
Available-for-sale securities		0		0
Level 1 | Fixed maturities | Other corporate
Assets:
Available-for-sale securities		0		0
Level 1 | Equity securities
Assets:
Available-for-sale securities				1,001
Level 2
Assets:
Available-for-sale securities		53,272		53,790
Equity securities		77
Asset derivatives		556		180
Other Investments				0
Cash and cash equivalents		0		0
Total assets		53,905		53,976
Liabilities:
Total liabilities		267		346
Level 2 | Foreign currency swaps
Assets:
Asset derivatives		130		146
Liabilities:
Liability derivatives		179		69
Level 2 | Foreign currency forwards
Assets:
Asset derivatives		426		22
Liabilities:
Liability derivatives		85		274
Level 2 | Foreign currency options
Assets:
Asset derivatives				12
Liabilities:
Liability derivatives		3		3
Level 2 | Credit default swaps
Assets:
Asset derivatives		0		0
Level 2 | Fixed maturities
Assets:
Available-for-sale securities		53,272		53,790
Level 2 | Fixed maturities | Government and agencies
Assets:
Available-for-sale securities		1,411		1,121
Level 2 | Fixed maturities | Municipalities
Assets:
Available-for-sale securities		1,373		1,370
Level 2 | Fixed maturities | Mortgage- and asset-backed securities
Assets:
Available-for-sale securities		269		269
Level 2 | Fixed maturities | Public utilities
Assets:
Available-for-sale securities		7,724		7,886
Level 2 | Fixed maturities | Sovereign and supranational
Assets:
Available-for-sale securities		1,866		1,909
Level 2 | Fixed maturities | Banks/financial institutions
Assets:
Available-for-sale securities		9,120		8,908
Level 2 | Fixed maturities | Other corporate
Assets:
Available-for-sale securities		31,509		32,327
Level 2 | Equity securities
Assets:
Available-for-sale securities				6
Level 3
Assets:
Available-for-sale securities		436		414
Equity securities		16
Asset derivatives		241		151
Other Investments				0
Cash and cash equivalents		0		0
Total assets		693		581
Liabilities:
Total liabilities		86		128
Level 3 | Foreign currency swaps
Assets:
Asset derivatives		240		150
Liabilities:
Liability derivatives		86		128
Level 3 | Foreign currency forwards
Assets:
Asset derivatives		0		0
Liabilities:
Liability derivatives		0		0
Level 3 | Foreign currency options
Assets:
Asset derivatives				0
Liabilities:
Liability derivatives		0		0
Level 3 | Credit default swaps
Assets:
Asset derivatives		1		1
Level 3 | Fixed maturities
Assets:
Available-for-sale securities		436		414
Level 3 | Fixed maturities | Government and agencies
Assets:
Available-for-sale securities		0		0
Level 3 | Fixed maturities | Municipalities
Assets:
Available-for-sale securities		0		0
Level 3 | Fixed maturities | Mortgage- and asset-backed securities
Assets:
Available-for-sale securities		186		175
Level 3 | Fixed maturities | Public utilities
Assets:
Available-for-sale securities		83		68
Level 3 | Fixed maturities | Sovereign and supranational
Assets:
Available-for-sale securities		0		0
Level 3 | Fixed maturities | Banks/financial institutions
Assets:
Available-for-sale securities		24		25
Level 3 | Fixed maturities | Other corporate
Assets:
Available-for-sale securities		$ 143		146
Level 3 | Equity securities
Assets:
Available-for-sale securities				$ 16
[1]	Includes perpetual securities
[2]	Includes perpetual securities ($1,506 at amortized cost and $1,774 at fair value)
[3]	Includes perpetual securities ($1,462 at amortized cost and $1,789 at fair value)
[4]	Includes perpetual securities ($71 at fair value)

FAIR VALUE MEASUREMENTS - Fai58

FAIR VALUE MEASUREMENTS - Fair Value Hierarchy Levels of Assets and Liabilities Carried at Cost or Amortized Cost (Details) - USD ($) $ in Millions		Mar. 31, 2018		Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments	[1]	$ 5,073		$ 3,402
Assets:
Securities held to maturity, fixed maturities, amortized cost		33,377		31,430
Securities held to maturity, fixed maturities, fair value		40,468		38,072
Other investments carried at amortized cost		4,608	[2]	3,017	[3]
Other investments carried at amortized cost, fair value		4,590	[2]	3,002	[3]
Total financial instruments assets not carried at fair value		37,985		34,447
Assets fair value disclosure financial instruments carried at cost		45,058		41,074
Liabilities:
Other policyholder funds		7,417		6,939
Other policyholders' funds fair value disclosure		7,307		6,841
Notes payable		5,352		5,267
Notes payable fair value disclosure		5,427		5,553
Total financial instrument liabilities not carried at fair value		12,769		12,206
Liabilities fair value disclosure financial instruments carried at cost		12,734		12,394
Fixed maturities
Assets:
Securities held to maturity, fixed maturities, fair value		40,468		38,072
Government and agencies | Fixed maturities
Assets:
Securities held to maturity, fixed maturities, amortized cost		22,686		21,331
Securities held to maturity, fixed maturities, fair value		28,317		26,491
Municipalities | Fixed maturities
Assets:
Securities held to maturity, fixed maturities, amortized cost		379		357
Securities held to maturity, fixed maturities, fair value		493		462
Mortgage- and asset-backed securities | Fixed maturities
Assets:
Securities held to maturity, fixed maturities, amortized cost		26		26
Securities held to maturity, fixed maturities, fair value		28		27
Public utilities | Fixed maturities
Assets:
Securities held to maturity, fixed maturities, amortized cost		3,508		3,300
Securities held to maturity, fixed maturities, fair value		3,891		3,698
Sovereign and supranational | Fixed maturities
Assets:
Securities held to maturity, fixed maturities, amortized cost		1,620		1,523
Securities held to maturity, fixed maturities, fair value		1,919		1,835
Banks/financial institutions | Fixed maturities
Assets:
Securities held to maturity, fixed maturities, amortized cost		2,300		2,206
Securities held to maturity, fixed maturities, fair value		2,477		2,387
Other corporate | Fixed maturities
Assets:
Securities held to maturity, fixed maturities, amortized cost		2,858		2,687
Securities held to maturity, fixed maturities, fair value		3,343		3,172
Policy loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments		227		210
Equity method investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments		238		118
Level 1
Assets:
Other investments carried at amortized cost, fair value		0	[2]	0	[3]
Assets fair value disclosure financial instruments carried at cost		28,317		26,491
Liabilities:
Other policyholders' funds fair value disclosure		0		0
Notes payable fair value disclosure		0		0
Liabilities fair value disclosure financial instruments carried at cost		0		0
Level 1 | Fixed maturities
Assets:
Securities held to maturity, fixed maturities, fair value		28,317		26,491
Level 1 | Government and agencies | Fixed maturities
Assets:
Securities held to maturity, fixed maturities, fair value		28,317		26,491
Level 1 | Municipalities | Fixed maturities
Assets:
Securities held to maturity, fixed maturities, fair value		0		0
Level 1 | Mortgage- and asset-backed securities | Fixed maturities
Assets:
Securities held to maturity, fixed maturities, fair value		0		0
Level 1 | Public utilities | Fixed maturities
Assets:
Securities held to maturity, fixed maturities, fair value		0		0
Level 1 | Sovereign and supranational | Fixed maturities
Assets:
Securities held to maturity, fixed maturities, fair value		0		0
Level 1 | Banks/financial institutions | Fixed maturities
Assets:
Securities held to maturity, fixed maturities, fair value		0		0
Level 1 | Other corporate | Fixed maturities
Assets:
Securities held to maturity, fixed maturities, fair value		0		0
Level 2
Assets:
Other investments carried at amortized cost, fair value		15	[2]	15	[3]
Assets fair value disclosure financial instruments carried at cost		12,147		11,577
Liabilities:
Other policyholders' funds fair value disclosure		0		0
Notes payable fair value disclosure		5,146		5,288
Liabilities fair value disclosure financial instruments carried at cost		5,146		5,288
Level 2 | Fixed maturities
Assets:
Securities held to maturity, fixed maturities, fair value		12,132		11,562
Level 2 | Government and agencies | Fixed maturities
Assets:
Securities held to maturity, fixed maturities, fair value		0		0
Level 2 | Municipalities | Fixed maturities
Assets:
Securities held to maturity, fixed maturities, fair value		493		462
Level 2 | Mortgage- and asset-backed securities | Fixed maturities
Assets:
Securities held to maturity, fixed maturities, fair value		9		8
Level 2 | Public utilities | Fixed maturities
Assets:
Securities held to maturity, fixed maturities, fair value		3,891		3,698
Level 2 | Sovereign and supranational | Fixed maturities
Assets:
Securities held to maturity, fixed maturities, fair value		1,919		1,835
Level 2 | Banks/financial institutions | Fixed maturities
Assets:
Securities held to maturity, fixed maturities, fair value		2,477		2,387
Level 2 | Other corporate | Fixed maturities
Assets:
Securities held to maturity, fixed maturities, fair value		3,343		3,172
Level 3
Assets:
Other investments carried at amortized cost, fair value		4,575	[2]	2,987	[3]
Assets fair value disclosure financial instruments carried at cost		4,594		3,006
Liabilities:
Other policyholders' funds fair value disclosure		7,307		6,841
Notes payable fair value disclosure		281		265
Liabilities fair value disclosure financial instruments carried at cost		7,588		7,106
Level 3 | Fixed maturities
Assets:
Securities held to maturity, fixed maturities, fair value		19		19
Level 3 | Government and agencies | Fixed maturities
Assets:
Securities held to maturity, fixed maturities, fair value		0		0
Level 3 | Municipalities | Fixed maturities
Assets:
Securities held to maturity, fixed maturities, fair value		0		0
Level 3 | Mortgage- and asset-backed securities | Fixed maturities
Assets:
Securities held to maturity, fixed maturities, fair value		19		19
Level 3 | Public utilities | Fixed maturities
Assets:
Securities held to maturity, fixed maturities, fair value		0		0
Level 3 | Sovereign and supranational | Fixed maturities
Assets:
Securities held to maturity, fixed maturities, fair value		0		0
Level 3 | Banks/financial institutions | Fixed maturities
Assets:
Securities held to maturity, fixed maturities, fair value		0		0
Level 3 | Other corporate | Fixed maturities
Assets:
Securities held to maturity, fixed maturities, fair value		$ 0		$ 0
[1]	Includes $3,994 in 2018 and $2,341 in 2017 of loan receivables and limited partnerships from consolidated variable interest entities
[2]	Excludes policy loans of $227 and equity method investments of $238, at carrying value
[3]	Excludes policy loans of $210 and equity method investments of $118, at carrying value

FAIR VALUE MEASUREMENTS - Fai59

FAIR VALUE MEASUREMENTS - Fair Value Hierarchy Levels of Assets by Pricing Source, Securities Carried at Fair Value (Details) - USD ($) $ in Millions		Mar. 31, 2018		Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	[1]	$ 89,033	[2]	$ 84,313	[3]
Equity securities	[1],[4]	1,108
Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities		35,325		30,109
Equity securities		1,015
Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities		53,272		53,790
Equity securities		77
Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities		436		414
Equity securities		16
Third party pricing vendor valuation technique
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities		1,092
Third party pricing vendor valuation technique | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities		1,015
Third party pricing vendor valuation technique | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities		77
Third party pricing vendor valuation technique | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities		0
Net asset value valuation technique
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities		16
Net asset value valuation technique | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities		0
Net asset value valuation technique | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities		0
Net asset value valuation technique | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities		16
Fixed maturities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	[1]	89,033		84,313
Fixed maturities | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities		35,325		30,109
Fixed maturities | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities		53,272		53,790
Fixed maturities | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities		436		414
Equity securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities				1,023
Equity securities | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities				1,001
Equity securities | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities				6
Equity securities | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities				16
Equity securities | Third party pricing vendor valuation technique
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities				1,007
Equity securities | Third party pricing vendor valuation technique | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities				1,001
Equity securities | Third party pricing vendor valuation technique | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities				6
Equity securities | Third party pricing vendor valuation technique | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities				0
Equity securities | Net asset value valuation technique
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities				16
Equity securities | Net asset value valuation technique | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities				0
Equity securities | Net asset value valuation technique | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities				0
Equity securities | Net asset value valuation technique | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities				16
Government and agencies | Fixed maturities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities		36,736		31,230
Government and agencies | Fixed maturities | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities		35,325		30,109
Government and agencies | Fixed maturities | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities		1,411		1,121
Government and agencies | Fixed maturities | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities		0		0
Government and agencies | Fixed maturities | Third party pricing vendor valuation technique
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities		36,736		31,230
Government and agencies | Fixed maturities | Third party pricing vendor valuation technique | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities		35,325		30,109
Government and agencies | Fixed maturities | Third party pricing vendor valuation technique | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities		1,411		1,121
Government and agencies | Fixed maturities | Third party pricing vendor valuation technique | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities		0		0
Municipalities | Fixed maturities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities		1,373		1,370
Municipalities | Fixed maturities | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities		0		0
Municipalities | Fixed maturities | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities		1,373		1,370
Municipalities | Fixed maturities | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities		0		0
Municipalities | Fixed maturities | Third party pricing vendor valuation technique
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities		1,373		1,370
Municipalities | Fixed maturities | Third party pricing vendor valuation technique | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities		0		0
Municipalities | Fixed maturities | Third party pricing vendor valuation technique | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities		1,373		1,370
Municipalities | Fixed maturities | Third party pricing vendor valuation technique | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities		0		0
Mortgage- and asset-backed securities | Fixed maturities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities		455		444
Mortgage- and asset-backed securities | Fixed maturities | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities		0		0
Mortgage- and asset-backed securities | Fixed maturities | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities		269		269
Mortgage- and asset-backed securities | Fixed maturities | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities		186		175
Mortgage- and asset-backed securities | Fixed maturities | Third party pricing vendor valuation technique
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities		269		269
Mortgage- and asset-backed securities | Fixed maturities | Third party pricing vendor valuation technique | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities		0		0
Mortgage- and asset-backed securities | Fixed maturities | Third party pricing vendor valuation technique | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities		269		269
Mortgage- and asset-backed securities | Fixed maturities | Third party pricing vendor valuation technique | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities		0		0
Mortgage- and asset-backed securities | Fixed maturities | Consensus pricing valuation technique
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities		186		175
Mortgage- and asset-backed securities | Fixed maturities | Consensus pricing valuation technique | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities		0		0
Mortgage- and asset-backed securities | Fixed maturities | Consensus pricing valuation technique | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities		0		0
Mortgage- and asset-backed securities | Fixed maturities | Consensus pricing valuation technique | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities		186		175
Public utilities | Fixed maturities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities		7,807		7,954
Public utilities | Fixed maturities | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities		0		0
Public utilities | Fixed maturities | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities		7,724		7,886
Public utilities | Fixed maturities | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities		83		68
Public utilities | Fixed maturities | Third party pricing vendor valuation technique
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities		7,724		7,886
Public utilities | Fixed maturities | Third party pricing vendor valuation technique | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities		0		0
Public utilities | Fixed maturities | Third party pricing vendor valuation technique | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities		7,724		7,886
Public utilities | Fixed maturities | Third party pricing vendor valuation technique | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities		0		0
Public utilities | Fixed maturities | Discounted cash flow valuation technique
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities		83		68
Public utilities | Fixed maturities | Discounted cash flow valuation technique | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities		0		0
Public utilities | Fixed maturities | Discounted cash flow valuation technique | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities		0		0
Public utilities | Fixed maturities | Discounted cash flow valuation technique | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities		83		68
Sovereign and supranational | Fixed maturities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities		1,866		1,909
Sovereign and supranational | Fixed maturities | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities		0		0
Sovereign and supranational | Fixed maturities | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities		1,866		1,909
Sovereign and supranational | Fixed maturities | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities		0		0
Sovereign and supranational | Fixed maturities | Third party pricing vendor valuation technique
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities		1,866		1,807
Sovereign and supranational | Fixed maturities | Third party pricing vendor valuation technique | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities		0		0
Sovereign and supranational | Fixed maturities | Third party pricing vendor valuation technique | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities		1,866		1,807
Sovereign and supranational | Fixed maturities | Third party pricing vendor valuation technique | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities		0		0
Sovereign and supranational | Fixed maturities | Consensus pricing valuation technique
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities				102
Sovereign and supranational | Fixed maturities | Consensus pricing valuation technique | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities				0
Sovereign and supranational | Fixed maturities | Consensus pricing valuation technique | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities				102
Sovereign and supranational | Fixed maturities | Consensus pricing valuation technique | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities				0
Banks/financial institutions | Fixed maturities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities		9,144		8,933
Banks/financial institutions | Fixed maturities | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities		0		0
Banks/financial institutions | Fixed maturities | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities		9,120		8,908
Banks/financial institutions | Fixed maturities | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities		24		25
Banks/financial institutions | Fixed maturities | Third party pricing vendor valuation technique
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities		9,120		8,908
Banks/financial institutions | Fixed maturities | Third party pricing vendor valuation technique | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities		0		0
Banks/financial institutions | Fixed maturities | Third party pricing vendor valuation technique | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities		9,120		8,908
Banks/financial institutions | Fixed maturities | Third party pricing vendor valuation technique | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities		0		0
Banks/financial institutions | Fixed maturities | Consensus pricing valuation technique
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities		24		25
Banks/financial institutions | Fixed maturities | Consensus pricing valuation technique | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities		0		0
Banks/financial institutions | Fixed maturities | Consensus pricing valuation technique | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities		0		0
Banks/financial institutions | Fixed maturities | Consensus pricing valuation technique | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities		24		25
Other corporate | Fixed maturities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities		31,652		32,473
Other corporate | Fixed maturities | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities		0		0
Other corporate | Fixed maturities | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities		31,509		32,327
Other corporate | Fixed maturities | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities		143		146
Other corporate | Fixed maturities | Third party pricing vendor valuation technique
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities		31,509		32,327
Other corporate | Fixed maturities | Third party pricing vendor valuation technique | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities		0		0
Other corporate | Fixed maturities | Third party pricing vendor valuation technique | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities		31,509		32,327
Other corporate | Fixed maturities | Third party pricing vendor valuation technique | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities		0		0
Other corporate | Fixed maturities | Discounted cash flow valuation technique
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities		143		146
Other corporate | Fixed maturities | Discounted cash flow valuation technique | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities		0		0
Other corporate | Fixed maturities | Discounted cash flow valuation technique | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities		0		0
Other corporate | Fixed maturities | Discounted cash flow valuation technique | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities		$ 143		$ 146
[1]	Includes perpetual securities
[2]	Includes perpetual securities ($1,506 at amortized cost and $1,774 at fair value)
[3]	Includes perpetual securities ($1,462 at amortized cost and $1,789 at fair value)
[4]	Includes perpetual securities ($71 at fair value)

FAIR VALUE MEASUREMENTS - Fai60

FAIR VALUE MEASUREMENTS - Fair Value Hierarchy Levels of Assets by Pricing Source, Securities Carried at Amortized Cost (Details) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity, fixed maturities, fair value	$ 40,468	$ 38,072
Fixed maturities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity, fixed maturities, fair value	40,468	38,072
Fixed maturities | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity, fixed maturities, fair value	28,317	26,491
Fixed maturities | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity, fixed maturities, fair value	12,132	11,562
Fixed maturities | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity, fixed maturities, fair value	19	19
Government and agencies | Fixed maturities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity, fixed maturities, fair value	28,317	26,491
Government and agencies | Fixed maturities | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity, fixed maturities, fair value	28,317	26,491
Government and agencies | Fixed maturities | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity, fixed maturities, fair value	0	0
Government and agencies | Fixed maturities | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity, fixed maturities, fair value	0	0
Government and agencies | Fixed maturities | Third party pricing vendor valuation technique
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity, fixed maturities, fair value	28,317	26,491
Government and agencies | Fixed maturities | Third party pricing vendor valuation technique | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity, fixed maturities, fair value	28,317	26,491
Government and agencies | Fixed maturities | Third party pricing vendor valuation technique | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity, fixed maturities, fair value	0	0
Government and agencies | Fixed maturities | Third party pricing vendor valuation technique | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity, fixed maturities, fair value	0	0
Municipalities | Fixed maturities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity, fixed maturities, fair value	493	462
Municipalities | Fixed maturities | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity, fixed maturities, fair value	0	0
Municipalities | Fixed maturities | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity, fixed maturities, fair value	493	462
Municipalities | Fixed maturities | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity, fixed maturities, fair value	0	0
Municipalities | Fixed maturities | Third party pricing vendor valuation technique
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity, fixed maturities, fair value	493	462
Municipalities | Fixed maturities | Third party pricing vendor valuation technique | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity, fixed maturities, fair value	0	0
Municipalities | Fixed maturities | Third party pricing vendor valuation technique | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity, fixed maturities, fair value	493	462
Municipalities | Fixed maturities | Third party pricing vendor valuation technique | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity, fixed maturities, fair value	0	0
Mortgage- and asset-backed securities | Fixed maturities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity, fixed maturities, fair value	28	27
Mortgage- and asset-backed securities | Fixed maturities | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity, fixed maturities, fair value	0	0
Mortgage- and asset-backed securities | Fixed maturities | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity, fixed maturities, fair value	9	8
Mortgage- and asset-backed securities | Fixed maturities | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity, fixed maturities, fair value	19	19
Mortgage- and asset-backed securities | Fixed maturities | Third party pricing vendor valuation technique
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity, fixed maturities, fair value	9	8
Mortgage- and asset-backed securities | Fixed maturities | Third party pricing vendor valuation technique | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity, fixed maturities, fair value	0	0
Mortgage- and asset-backed securities | Fixed maturities | Third party pricing vendor valuation technique | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity, fixed maturities, fair value	9	8
Mortgage- and asset-backed securities | Fixed maturities | Third party pricing vendor valuation technique | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity, fixed maturities, fair value	0	0
Mortgage- and asset-backed securities | Fixed maturities | Consensus pricing valuation technique
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity, fixed maturities, fair value	19	19
Mortgage- and asset-backed securities | Fixed maturities | Consensus pricing valuation technique | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity, fixed maturities, fair value	0	0
Mortgage- and asset-backed securities | Fixed maturities | Consensus pricing valuation technique | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity, fixed maturities, fair value	0	0
Mortgage- and asset-backed securities | Fixed maturities | Consensus pricing valuation technique | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity, fixed maturities, fair value	19	19
Public utilities | Fixed maturities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity, fixed maturities, fair value	3,891	3,698
Public utilities | Fixed maturities | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity, fixed maturities, fair value	0	0
Public utilities | Fixed maturities | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity, fixed maturities, fair value	3,891	3,698
Public utilities | Fixed maturities | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity, fixed maturities, fair value	0	0
Public utilities | Fixed maturities | Third party pricing vendor valuation technique
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity, fixed maturities, fair value	3,891	3,698
Public utilities | Fixed maturities | Third party pricing vendor valuation technique | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity, fixed maturities, fair value	0	0
Public utilities | Fixed maturities | Third party pricing vendor valuation technique | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity, fixed maturities, fair value	3,891	3,698
Public utilities | Fixed maturities | Third party pricing vendor valuation technique | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity, fixed maturities, fair value	0	0
Sovereign and supranational | Fixed maturities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity, fixed maturities, fair value	1,919	1,835
Sovereign and supranational | Fixed maturities | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity, fixed maturities, fair value	0	0
Sovereign and supranational | Fixed maturities | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity, fixed maturities, fair value	1,919	1,835
Sovereign and supranational | Fixed maturities | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity, fixed maturities, fair value	0	0
Sovereign and supranational | Fixed maturities | Third party pricing vendor valuation technique
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity, fixed maturities, fair value	1,919	1,835
Sovereign and supranational | Fixed maturities | Third party pricing vendor valuation technique | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity, fixed maturities, fair value	0	0
Sovereign and supranational | Fixed maturities | Third party pricing vendor valuation technique | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity, fixed maturities, fair value	1,919	1,835
Sovereign and supranational | Fixed maturities | Third party pricing vendor valuation technique | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity, fixed maturities, fair value	0	0
Banks/financial institutions | Fixed maturities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity, fixed maturities, fair value	2,477	2,387
Banks/financial institutions | Fixed maturities | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity, fixed maturities, fair value	0	0
Banks/financial institutions | Fixed maturities | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity, fixed maturities, fair value	2,477	2,387
Banks/financial institutions | Fixed maturities | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity, fixed maturities, fair value	0	0
Banks/financial institutions | Fixed maturities | Third party pricing vendor valuation technique
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity, fixed maturities, fair value	2,477	2,387
Banks/financial institutions | Fixed maturities | Third party pricing vendor valuation technique | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity, fixed maturities, fair value	0	0
Banks/financial institutions | Fixed maturities | Third party pricing vendor valuation technique | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity, fixed maturities, fair value	2,477	2,387
Banks/financial institutions | Fixed maturities | Third party pricing vendor valuation technique | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity, fixed maturities, fair value	0	0
Other corporate | Fixed maturities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity, fixed maturities, fair value	3,343	3,172
Other corporate | Fixed maturities | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity, fixed maturities, fair value	0	0
Other corporate | Fixed maturities | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity, fixed maturities, fair value	3,343	3,172
Other corporate | Fixed maturities | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity, fixed maturities, fair value	0	0
Other corporate | Fixed maturities | Third party pricing vendor valuation technique
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity, fixed maturities, fair value	3,343	3,172
Other corporate | Fixed maturities | Third party pricing vendor valuation technique | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity, fixed maturities, fair value	0	0
Other corporate | Fixed maturities | Third party pricing vendor valuation technique | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity, fixed maturities, fair value	3,343	3,172
Other corporate | Fixed maturities | Third party pricing vendor valuation technique | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity, fixed maturities, fair value	$ 0	$ 0

FAIR VALUE MEASUREMENTS - Chang

FAIR VALUE MEASUREMENTS - Changes in Investments and Derivatives Carried at Fair Value Classified as Level 3 (Detail) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2018	Mar. 31, 2017
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period		$ 453	$ 223
Realized investment gains (losses) included in earnings		126	38
Unrealized gains (losses) included in other comprehensive income (loss)		13	7
Purchases		16	37
Issuances		0	0
Sales		0	(1)
Settlements		(1)	(9)
Transfers into Level 3		0	0
Transfers out of Level 3		0	0
Balance, end of period		607	295
Change in unrealized gains (losses) still held		126	38
Foreign currency swaps
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Balance, beginning of period	[1]	22	(21)
Realized gains or losses included in earnings	[1]	126	38
Unrealized gains or losses included in other comprehensive income (loss)	[1]	6	2
Purchases	[1]	0	0
Issuances	[1]	0	0
Sales	[1]	0	0
Settlements	[1]	0	0
Transfers into Level 3	[1]	0	0
Transfers out of Level 3	[1]	0	0
Balance, end of period	[1]	154	19
Changes in unrealized gain (losses) still held	[1]	126	38
Credit default swaps
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Balance, beginning of period	[1]	1	2
Realized gains or losses included in earnings	[1]	0	0
Unrealized gains or losses included in other comprehensive income (loss)	[1]	0	0
Purchases	[1]	0	0
Issuances	[1]	0	0
Sales	[1]	0	0
Settlements	[1]	0	0
Transfers into Level 3	[1]	0	0
Transfers out of Level 3	[1]	0	0
Balance, end of period	[1]	1	2
Changes in unrealized gain (losses) still held	[1]	0	0
Fixed maturities | Mortgage- and asset-backed securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period		175	198
Realized investment gains (losses) included in earnings		0	0
Unrealized gains (losses) included in other comprehensive income (loss)		11	6
Purchases		0	0
Issuances		0	0
Sales		0	0
Settlements		0	(9)
Transfers into Level 3		0	0
Transfers out of Level 3		0	0
Balance, end of period		186	195
Change in unrealized gains (losses) still held		0	0
Fixed maturities | Public utilities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period		68	16
Realized investment gains (losses) included in earnings		0	0
Unrealized gains (losses) included in other comprehensive income (loss)		(1)	0
Purchases		16	0
Issuances		0	0
Sales		0	0
Settlements		0	0
Transfers into Level 3		0	0
Transfers out of Level 3		0	0
Balance, end of period		83	16
Change in unrealized gains (losses) still held		0	0
Fixed maturities | Banks/financial institutions
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period		25	25
Realized investment gains (losses) included in earnings		0	0
Unrealized gains (losses) included in other comprehensive income (loss)		(1)	(1)
Purchases		0	0
Issuances		0	0
Sales		0	0
Settlements		0	0
Transfers into Level 3		0	0
Transfers out of Level 3		0	0
Balance, end of period		24	24
Change in unrealized gains (losses) still held		0	0
Fixed maturities | Other corporate
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period		146	0
Realized investment gains (losses) included in earnings		0	0
Unrealized gains (losses) included in other comprehensive income (loss)		(2)	0
Purchases		0	35
Issuances		0	0
Sales		0	0
Settlements		(1)	0
Transfers into Level 3		0	0
Transfers out of Level 3		0	0
Balance, end of period		143	35
Change in unrealized gains (losses) still held		0	0
Equity securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period		16	3
Realized investment gains (losses) included in earnings		0	0
Unrealized gains (losses) included in other comprehensive income (loss)		0	0
Purchases		0	2
Issuances		0	0
Sales		0	(1)
Settlements		0	0
Transfers into Level 3		0	0
Transfers out of Level 3		0	0
Balance, end of period		16	4
Change in unrealized gains (losses) still held		$ 0	$ 0
[1]	Derivative assets and liabilities are presented net

FAIR VALUE MEASUREMENTS - Addit

FAIR VALUE MEASUREMENTS - Additional Information (Detail) - USD ($) $ in Millions	Mar. 31, 2018	Mar. 31, 2017
Fair Value Disclosures [Abstract]
Fair Value, Assets, Level 1 to Level 2 Transfers, Amount	$ 0	$ 0
Fair Value, Assets, Level 2 to Level 1 Transfers, Amount	$ 0	$ 0

FAIR VALUE MEASUREMENTS - Fai63

FAIR VALUE MEASUREMENTS - Fair Value Inputs Assets Quantitative Information (Details) - USD ($) $ in Millions		3 Months Ended		12 Months Ended
		Mar. 31, 2018		Dec. 31, 2017
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Available-for-sale securities	[1]	$ 89,033	[2]	$ 84,313	[3]
Equity securities	[1],[4]	1,108
Asset derivatives		797		331
Assets, fair value		95,018		89,215
Level 3
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Available-for-sale securities		436		414
Equity securities		16
Asset derivatives		241		151
Assets, fair value		693		581
Net asset value valuation technique
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Equity securities		16
Net asset value valuation technique | Level 3
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Equity securities		16
Fixed maturities
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Available-for-sale securities	[1]	89,033		84,313
Fixed maturities | Level 3
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Available-for-sale securities		436		414
Equity securities
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Available-for-sale securities				1,023
Equity securities | Level 3
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Available-for-sale securities				16
Equity securities | Net asset value valuation technique
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Available-for-sale securities				16
Equity securities | Net asset value valuation technique | Level 3
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Available-for-sale securities				16
Mortgage- and asset-backed securities | Fixed maturities
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Available-for-sale securities		455		444
Mortgage- and asset-backed securities | Fixed maturities | Level 3
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Available-for-sale securities		186		175
Mortgage- and asset-backed securities | Fixed maturities | Consensus pricing valuation technique
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Available-for-sale securities		186		175
Mortgage- and asset-backed securities | Fixed maturities | Consensus pricing valuation technique | Level 3
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Available-for-sale securities		186		175
Public utilities | Fixed maturities
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Available-for-sale securities		7,807		7,954
Public utilities | Fixed maturities | Level 3
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Available-for-sale securities		83		68
Public utilities | Fixed maturities | Discounted cash flow valuation technique
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Available-for-sale securities		83		68
Public utilities | Fixed maturities | Discounted cash flow valuation technique | Level 3
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Available-for-sale securities		83		68
Banks/financial institutions | Fixed maturities
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Available-for-sale securities		9,144		8,933
Banks/financial institutions | Fixed maturities | Level 3
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Available-for-sale securities		24		25
Banks/financial institutions | Fixed maturities | Consensus pricing valuation technique
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Available-for-sale securities		24		25
Banks/financial institutions | Fixed maturities | Consensus pricing valuation technique | Level 3
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Available-for-sale securities		24		25
Other corporate | Fixed maturities
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Available-for-sale securities		31,652		32,473
Other corporate | Fixed maturities | Level 3
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Available-for-sale securities		143		146
Other corporate | Fixed maturities | Discounted cash flow valuation technique
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Available-for-sale securities		143		146
Other corporate | Fixed maturities | Discounted cash flow valuation technique | Level 3
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Available-for-sale securities		143		146
Foreign currency swaps
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Asset derivatives		370		296
Foreign currency swaps | Level 3
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Asset derivatives		240		150
Credit default swaps
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Asset derivatives		1		1
Credit default swaps | Level 3
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Asset derivatives		1		1
Fair Value, Unobservable Input, Interest Rates (USD), Interest Rates (JPY) and CDS Spreads | Foreign currency swaps | Discounted cash flow valuation technique | Level 3
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Asset derivatives		$ 185		$ 80
Fair Value, Unobservable Input, Interest Rates (USD), Interest Rates (JPY) and CDS Spreads | Foreign currency swaps | Assets | Lower Limit | Level 3
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value Inputs, Entity Credit Risk		0.13%		0.09%
Fair Value, Unobservable Input, Interest Rates (USD), Interest Rates (JPY) and CDS Spreads | Foreign currency swaps | Assets | Upper Limit | Level 3
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value Inputs, Entity Credit Risk		1.01%		0.90%
Fair Value, Unobservable Input, Interest Rates (USD) and Interest Rates (JPY) | Foreign currency swaps | Discounted cash flow valuation technique | Level 3
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Asset derivatives		$ 55		$ 70
Fair Value, Unobservable Input, Base Correlation, CDS Spreads, Recovery Rate | Credit default swaps | Discounted cash flow valuation technique | Level 3
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Asset derivatives		$ 1		$ 1
Fair Value, Unobservable Input, Base Correlation, CDS Spreads, Recovery Rate | Credit default swaps | Assets | Level 3
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value Inputs, Entity Credit Risk		0.15%		0.25%
Fair Value Inputs, Recovery Rate		37.24%		37.24%
Fair Value, Unobservable Input, Base Correlation, CDS Spreads, Recovery Rate | Credit default swaps | Assets | Lower Limit | Level 3
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value Inputs, Base Correlation	[5]	49.98%		46.33%
Fair Value, Unobservable Input, Base Correlation, CDS Spreads, Recovery Rate | Credit default swaps | Assets | Upper Limit | Level 3
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value Inputs, Base Correlation	[5]	54.13%		49.65%
Dollar-denominated
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Equity securities		$ 397
Dollar-denominated | Fixed maturities
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Available-for-sale securities		37,233		$ 38,703
Dollar-denominated | Equity securities
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Available-for-sale securities				328
Dollar-denominated | Mortgage- and asset-backed securities | Fixed maturities
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Available-for-sale securities		171		173
Dollar-denominated | Public utilities | Fixed maturities
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Available-for-sale securities		5,747		5,973
Dollar-denominated | Banks/financial institutions | Fixed maturities
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Available-for-sale securities		3,264		3,433
Dollar-denominated | Other corporate | Fixed maturities
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Available-for-sale securities		$ 26,561		$ 27,586
Dollar-denominated | Fair Value, Unobservable Input, Interest Rates (USD), Interest Rates (JPY) and CDS Spreads | Foreign currency swaps | Assets | Lower Limit | Level 3
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value Inputs, Discount Rate	[6]	2.78%		2.40%
Dollar-denominated | Fair Value, Unobservable Input, Interest Rates (USD), Interest Rates (JPY) and CDS Spreads | Foreign currency swaps | Assets | Upper Limit | Level 3
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value Inputs, Discount Rate	[6]	2.82%		2.54%
Dollar-denominated | Fair Value, Unobservable Input, Interest Rates (USD) and Interest Rates (JPY) | Foreign currency swaps | Assets | Lower Limit | Level 3
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value Inputs, Discount Rate	[6]	2.78%		2.40%
Dollar-denominated | Fair Value, Unobservable Input, Interest Rates (USD) and Interest Rates (JPY) | Foreign currency swaps | Assets | Upper Limit | Level 3
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value Inputs, Discount Rate	[6]	2.82%		2.54%
Yen-denominated
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Equity securities		$ 711
Yen-denominated | Fixed maturities
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Available-for-sale securities		51,800		$ 45,610
Yen-denominated | Equity securities
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Available-for-sale securities				695
Yen-denominated | Mortgage- and asset-backed securities | Fixed maturities
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Available-for-sale securities		284		271
Yen-denominated | Public utilities | Fixed maturities
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Available-for-sale securities		2,060		1,981
Yen-denominated | Banks/financial institutions | Fixed maturities
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Available-for-sale securities		5,880		5,500
Yen-denominated | Other corporate | Fixed maturities
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Available-for-sale securities		$ 5,091		$ 4,887
Yen-denominated | Fair Value, Unobservable Input, Interest Rates (USD), Interest Rates (JPY) and CDS Spreads | Foreign currency swaps | Assets | Lower Limit | Level 3
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value Inputs, Discount Rate	[7]	0.26%		0.26%
Yen-denominated | Fair Value, Unobservable Input, Interest Rates (USD), Interest Rates (JPY) and CDS Spreads | Foreign currency swaps | Assets | Upper Limit | Level 3
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value Inputs, Discount Rate	[7]	0.85%		0.85%
Yen-denominated | Fair Value, Unobservable Input, Interest Rates (USD) and Interest Rates (JPY) | Foreign currency swaps | Assets | Lower Limit | Level 3
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value Inputs, Discount Rate	[7]	0.26%		0.26%
Yen-denominated | Fair Value, Unobservable Input, Interest Rates (USD) and Interest Rates (JPY) | Foreign currency swaps | Assets | Upper Limit | Level 3
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value Inputs, Discount Rate	[7]	0.85%		0.85%
[1]	Includes perpetual securities
[2]	Includes perpetual securities ($1,506 at amortized cost and $1,774 at fair value)
[3]	Includes perpetual securities ($1,462 at amortized cost and $1,789 at fair value)
[4]	Includes perpetual securities ($71 at fair value)
[5]	Range of base correlation for the Company's bespoke tranche for attachment and detachment points corresponding to market indices
[6]	Inputs derived from U.S. long-term rates to accommodate long maturity nature of the Company's swaps
[7]	Inputs derived from Japan long-term rates to accommodate long maturity nature of the Company's swaps

FAIR VALUE MEASUREMENTS - Fai64

FAIR VALUE MEASUREMENTS - Fair Value Inputs Liabilities Quantitative Information (Details) - USD ($) $ in Millions		3 Months Ended	12 Months Ended
		Mar. 31, 2018	Dec. 31, 2017
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Liability derivatives		$ 353	$ 474
Liabilities, fair value disclosure		353	474
Level 3
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Liabilities, fair value disclosure		86	128
Foreign currency swaps
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Liability derivatives		265	197
Foreign currency swaps | Level 3
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Liability derivatives		86	128
Fair Value, Unobservable Input, Interest Rates (USD), Interest Rates (JPY) and CDS Spreads | Foreign currency swaps | Discounted cash flow valuation technique | Level 3
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Liability derivatives		$ 84	$ 120
Fair Value, Unobservable Input, Interest Rates (USD), Interest Rates (JPY) and CDS Spreads | Foreign currency swaps | Liability | Lower Limit | Level 3
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Fair Value Inputs, Entity Credit Risk		0.17%	0.13%
Fair Value, Unobservable Input, Interest Rates (USD), Interest Rates (JPY) and CDS Spreads | Foreign currency swaps | Liability | Upper Limit | Level 3
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Fair Value Inputs, Entity Credit Risk		1.70%	1.57%
Fair Value, Unobservable Input, Interest Rates (USD) and Interest Rates (JPY) | Foreign currency swaps | Discounted cash flow valuation technique | Level 3
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Liability derivatives		$ 2	$ 8
Dollar-denominated | Fair Value, Unobservable Input, Interest Rates (USD), Interest Rates (JPY) and CDS Spreads | Foreign currency swaps | Liability | Lower Limit | Level 3
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Fair Value Inputs, Discount Rate	[1]	2.78%	2.40%
Dollar-denominated | Fair Value, Unobservable Input, Interest Rates (USD), Interest Rates (JPY) and CDS Spreads | Foreign currency swaps | Liability | Upper Limit | Level 3
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Fair Value Inputs, Discount Rate	[1]	2.82%	2.54%
Dollar-denominated | Fair Value, Unobservable Input, Interest Rates (USD) and Interest Rates (JPY) | Foreign currency swaps | Liability | Lower Limit | Level 3
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Fair Value Inputs, Discount Rate	[1]	2.78%	2.40%
Dollar-denominated | Fair Value, Unobservable Input, Interest Rates (USD) and Interest Rates (JPY) | Foreign currency swaps | Liability | Upper Limit | Level 3
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Fair Value Inputs, Discount Rate	[1]	2.82%	2.54%
Yen-denominated | Fair Value, Unobservable Input, Interest Rates (USD), Interest Rates (JPY) and CDS Spreads | Foreign currency swaps | Liability | Lower Limit | Level 3
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Fair Value Inputs, Discount Rate	[2]	0.26%	0.26%
Yen-denominated | Fair Value, Unobservable Input, Interest Rates (USD), Interest Rates (JPY) and CDS Spreads | Foreign currency swaps | Liability | Upper Limit | Level 3
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Fair Value Inputs, Discount Rate	[2]	0.85%	0.85%
Yen-denominated | Fair Value, Unobservable Input, Interest Rates (USD) and Interest Rates (JPY) | Foreign currency swaps | Liability | Lower Limit | Level 3
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Fair Value Inputs, Discount Rate	[2]	0.26%	0.26%
Yen-denominated | Fair Value, Unobservable Input, Interest Rates (USD) and Interest Rates (JPY) | Foreign currency swaps | Liability | Upper Limit | Level 3
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Fair Value Inputs, Discount Rate	[2]	0.85%	0.85%
[1]	Inputs derived from U.S. long-term rates to accommodate long maturity nature of the Company's swaps
[2]	Inputs derived from Japan long-term rates to accommodate long maturity nature of the Company's swaps

POLICY LIABILITIES - Changes in

POLICY LIABILITIES - Changes in Liability for Unpaid Policy Claims (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Liability for Unpaid Claims and Claims Expenses
Net balance, beginning of period	$ 4,392
Less claims paid during the period on claims incurred during:
Net balance, end of period	4,630
Total liability for unpaid policy claims	4,630	$ 4,230
Health insurance
Liability for Unpaid Claims and Claims Expenses
Unpaid supplemental health claims, beginning of period	3,884	3,707
Less reinsurance recoverables	30	27
Net balance, beginning of period	3,854	3,680
Add claims incurred during the period related to:
Current year	1,842	1,737
Prior years	(192)	(111)
Total incurred	1,650	1,626
Less claims paid during the period on claims incurred during:
Current year	518	505
Prior years	1,116	1,055
Total paid	1,634	1,560
Effect of foreign exchange rate changes on unpaid claims	142	80
Net balance, end of period	4,012	3,826
Add reinsurance recoverables	31	29
Total liability for unpaid policy claims	4,043	3,855
Life insurance
Less claims paid during the period on claims incurred during:
Total liability for unpaid policy claims	$ 587	$ 375

POLICY LIABILITIES - Additional

POLICY LIABILITIES - Additional Information (Details) - Health insurance - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Liability for Future Policy Benefit, by Product Segment [Line Items]
Prior years claims and claims adjustment expense	$ (192)	$ (111)
Aflac Japan
Liability for Future Policy Benefit, by Product Segment [Line Items]
Prior years claims and claims adjustment expense	$ (97)
Percentage of total prior year claims and claims adjustment expense	51.00%
Liability for unpaid claims and claims adjustment expense, foreign currency translation gain (loss)	$ (5)
Prior year claims and claims adjustment expense excluding effect of foreign currency	$ (92)
Percentage of total prior year claims and claims adjustment expense excluding effect of foreign currency	48.00%

REINSURANCE - Additional Infor

REINSURANCE - Additional Information (Details) $ in Millions, ¥ in Billions	3 Months Ended
	Mar. 31, 2018JPY (¥)	Mar. 31, 2018USD ($)	Dec. 31, 2017USD ($)
Effects of Reinsurance [Line Items]
Percent change in spot yen/dollar exchange rate		6.40%
Percent change in ceded reserves		0.40%
Aflac Japan
Effects of Reinsurance [Line Items]
Committed reinsurance facility | ¥	¥ 110
Aflac Japan | Closed Block
Effects of Reinsurance [Line Items]
Reinsurance deferred profit liability		$ 1,000
Reinsurance recoverable		$ 969	$ 908

REINSURANCE - Effect of Reinsu

REINSURANCE - Effect of Reinsurance on Premiums and Benefits and Claims (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Effects of Reinsurance [Line Items]
Direct premium income	$ 4,833	$ 4,724
Net premium income	4,745	4,638
Direct benefits and claims	3,119	3,129
Benefits and claims, net	3,042	3,052
All other
Effects of Reinsurance [Line Items]
Ceded premiums	(15)	(12)
Assumed premiums earned	2	2
Ceded benefits and claims	(12)	(11)
Assumed benefits and claims from other companies	0	2
Aflac Japan
Effects of Reinsurance [Line Items]
Net premium income	3,263	3,194
Aflac Japan | Closed Block
Effects of Reinsurance [Line Items]
Ceded premiums	(129)	(130)
Assumed premiums earned	54	54
Ceded benefits and claims	(117)	(122)
Assumed benefits and claims from other companies	52	54
Intercompany eliminations
Effects of Reinsurance [Line Items]
Ceded benefits and claims	12	13
Assumed benefits and claims from other companies	$ (12)	$ (13)

NOTES PAYABLE - Additional Info

NOTES PAYABLE - Additional Information (Details) $ in Millions	Mar. 31, 2018USD ($)
Lines of credit
Debt Instrument [Line Items]
Debt instrument, debt default, amount	$ 0
Notes Payable
Debt Instrument [Line Items]
Debt instrument, debt default, amount	$ 0

NOTES PAYABLE - Summary of Note

NOTES PAYABLE - Summary of Notes Payable (Details) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Notes payable	$ 5,372	$ 5,289
2.40% senior notes due March 2020
Debt Instrument [Line Items]
Notes payable	548	548
4.00% senior notes due February 2022
Debt Instrument [Line Items]
Notes payable	348	348
3.625% senior notes due June 2023
Debt Instrument [Line Items]
Notes payable	697	697
3.625% senior notes due November 2024
Debt Instrument [Line Items]
Notes payable	746	745
3.25% senior notes due March 2025
Debt Instrument [Line Items]
Notes payable	446	446
2.875% senior notes due October 2026
Debt Instrument [Line Items]
Notes payable	297	297
6.90% senior notes due December 2039
Debt Instrument [Line Items]
Notes payable	220	220
6.45% senior notes due August 2040
Debt Instrument [Line Items]
Notes payable	254	254
4.00% senior notes due October 2046
Debt Instrument [Line Items]
Notes payable	394	394
.932% senior notes due January 2027
Debt Instrument [Line Items]
Notes payable	562	528
2.108% subordinated notes due October 2047
Debt Instrument [Line Items]
Notes payable	559	526
Yen-denominated loan variable interest rate due September 2021
Debt Instrument [Line Items]
Notes payable	47	44
Yen-denominated loan variable interest rate due September 2023
Debt Instrument [Line Items]
Notes payable	234	220
Capitalized lease obligations
Debt Instrument [Line Items]
Notes payable	$ 20	$ 22

NOTES PAYABLE - Summary of No71

NOTES PAYABLE - Summary of Notes Payable (Parenthetical) (Details) $ in Millions, ¥ in Billions	Mar. 31, 2018USD ($)	Mar. 31, 2018JPY (¥)	Dec. 31, 2017JPY (¥)
2.40% senior notes due March 2020
Debt Instrument [Line Items]
Debt instrument, interest rate	2.40%	2.40%	2.40%
Debt instrument, principal amount	$ 550
4.00% senior notes due February 2022
Debt Instrument [Line Items]
Debt instrument, interest rate	4.00%	4.00%	4.00%
Debt instrument, principal amount	$ 350
3.625% senior notes due June 2023
Debt Instrument [Line Items]
Debt instrument, interest rate	3.625%	3.625%	3.625%
Debt instrument, principal amount	$ 700
3.625% senior notes due November 2024
Debt Instrument [Line Items]
Debt instrument, interest rate	3.625%	3.625%	3.625%
Debt instrument, principal amount	$ 750
3.25% senior notes due March 2025
Debt Instrument [Line Items]
Debt instrument, interest rate	3.25%	3.25%	3.25%
Debt instrument, principal amount	$ 450
2.875% senior notes due October 2026
Debt Instrument [Line Items]
Debt instrument, interest rate	2.875%	2.875%	2.875%
6.90% senior notes due December 2039
Debt Instrument [Line Items]
Debt instrument, interest rate	6.90%	6.90%	6.90%
6.45% senior notes due August 2040
Debt Instrument [Line Items]
Debt instrument, interest rate	6.45%	6.45%	6.45%
4.00% senior notes due October 2046
Debt Instrument [Line Items]
Debt instrument, interest rate	4.00%	4.00%	4.00%
.932% senior notes due January 2027
Debt Instrument [Line Items]
Debt instrument, interest rate	0.932%	0.932%	0.932%
Debt instrument, principal amount | ¥		¥ 60	¥ 60
2.108% subordinated notes due October 2047
Debt Instrument [Line Items]
Debt instrument, interest rate	2.108%	2.108%	2.108%
Debt instrument, principal amount | ¥		¥ 60	¥ 60
Yen-denominated loan variable interest rate due September 2021
Debt Instrument [Line Items]
Debt instrument, interest rate	0.32%	0.32%	0.32%
Debt instrument, principal amount | ¥		¥ 5	¥ 5
Yen-denominated loan variable interest rate due September 2023
Debt Instrument [Line Items]
Debt instrument, interest rate	0.47%	0.47%	0.47%
Debt instrument, principal amount | ¥		¥ 25	¥ 25

NOTES PAYABLE - Summary of Line

NOTES PAYABLE - Summary of Lines of Credit (Details) - 3 months ended Mar. 31, 2018 ¥ in Millions, $ in Millions	USD ($)	JPY (¥)
$100 million line of credit
Line of Credit Facility [Line Items]
Line of credit facility, interest rate description	The rate quoted by the bank and agreed upon at the time of borrowing
Line of credit facility term	364 days
Line of credit facility, maximum borrowing capacity | $	$ 100
Line of credit facility, amount outstanding | $	$ 0
100.0 billion yen line of credit
Line of Credit Facility [Line Items]
Line of credit facility, interest rate description	A rate per annum equal to (a) Tokyo interbank market rate (TIBOR) plus, the alternative applicable TIBOR margin during the availability period from the closing date to the commitment termination date or (b) the TIBOR rate offered by the agent to major banks in yen for the applicable period plus, the applicable alternative TIBOR margin during the term out period
Line of credit facility term	3 years
Line of credit facility, maximum borrowing capacity | ¥		¥ 100,000
Line of credit facility, amount outstanding | ¥		0
55.0 billion yen line of credit
Line of Credit Facility [Line Items]
Line of credit facility, interest rate description	A rate per annum equal to, at the Company's option, either, (a) London Interbank Offered Rate (LIBOR) adjusted for certain costs or (b) a base rate determined by reference to the highest of (1) the federal funds rate plus 1/2 of 1%, (2) the rate of interest for such day announced by Mizuho Bank, Ltd. as its prime rate, or (3) the eurocurrency rate for an interest period of one month plus 1.00%, in each case plus an applicable margin
Line of credit facility term	5 years
Line of credit facility, maximum borrowing capacity | ¥		55,000
Line of credit facility, amount outstanding | ¥		0
$50 million line of credit
Line of Credit Facility [Line Items]
Line of credit facility, interest rate description	A rate per annum equal to, at the Parent Company's option, either (a) a eurocurrency rate determined by reference to the agent's LIBOR for the interest period relevant to such borrowing or (b) the base rate determined by reference to the greater of (i) the prime rate as determined by the agent, and (ii) the sum of 0.50% and the federal funds rate for such day
Line of credit facility, maximum borrowing capacity | $	$ 50
Line of credit facility, amount outstanding | $	$ 0
$250 million line of credit
Line of Credit Facility [Line Items]
Line of credit facility, interest rate description	USD three-month LIBOR plus 75 basis points per annum
Line of credit facility term	364 days
Line of credit facility, maximum borrowing capacity | $	$ 250
Line of credit facility, amount outstanding | $	$ 0
Debt instrument, term	3 months
37.5 billion yen line of credit
Line of Credit Facility [Line Items]
Line of credit facility, interest rate description	Three-month TIBOR plus 80 basis points per annum
Line of credit facility term	364 days
Line of credit facility, maximum borrowing capacity | ¥		37,500
Line of credit facility, amount outstanding | ¥		¥ 0
Debt instrument, term	3 months
Lower Limit | 100.0 billion yen line of credit
Line of Credit Facility [Line Items]
Line of credit facility, commitment fee percentage	0.30%
Lower Limit | 55.0 billion yen line of credit
Line of Credit Facility [Line Items]
Line of credit facility, commitment fee percentage	0.085%
Upper Limit | $100 million line of credit
Line of Credit Facility [Line Items]
Debt instrument, term	3 months
Upper Limit | 100.0 billion yen line of credit
Line of Credit Facility [Line Items]
Line of credit facility, commitment fee percentage	0.50%
Upper Limit | 55.0 billion yen line of credit
Line of Credit Facility [Line Items]
Line of credit facility, commitment fee percentage	0.225%
Upper Limit | $50 million line of credit
Line of Credit Facility [Line Items]
Debt instrument, term	3 months

INCOME TAXES (Details)

INCOME TAXES (Details) - USD ($) $ in Millions	1 Months Ended	3 Months Ended			12 Months Ended
	Jan. 31, 2018	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017	Dec. 31, 2017	Dec. 22, 2017
Income Taxes [Line Items]
Effective tax rate	21.00%	21.00%		35.00%	35.00%
Income Tax Expense, Gross, Continuing Operations, Adjustment of Deferred Tax Assets			$ 1,000
Income Tax Benefit, Gross, Continuing Operations, Adjustment of Deferred Tax Liabilities					$ 2,900
Income Tax Expense (Benefit), Continuing Operations, Adjustment of Deferred Tax Asset (Liability)			(1,900)		(1,900)
Deferred Tax Assets, Valuation Allowance			$ 700		$ 700
Aflac Japan
Income Taxes [Line Items]
Deferred Tax Liabilities, Net						$ 4,500

SHAREHOLDERS' EQUITY - Reconcil

SHAREHOLDERS' EQUITY - Reconciliation of Number of Shares of Common Stock (Detail) - shares shares in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Common Stock Issued [Roll Forward]
Balance, beginning of period	1,345,762	1,342,498
Exercise of stock options and issuance of restricted shares	1,014	868
Balance, end of period	1,346,776	1,343,366
Treasury Stock [Roll Forward]
Balance, beginning of period	564,852	530,877
Balance, end of period	571,019	547,361
Shares outstanding, end of period	775,757	796,005
Treasury Stock
Treasury Stock [Roll Forward]
Stock acquired in open market, shares	6,640	16,986
Other purchases	315	288
Shares issued to AFL Stock Plan	(384)	(494)
Exercise of stock options	(305)	(256)
Other dispositions	(99)	(40)

SHAREHOLDERS' EQUITY - Anti-Dil

SHAREHOLDERS' EQUITY - Anti-Dilutive Share-Based Awards Excluded from Calculation of Diluted Earnings Per Share (Detail) - shares shares in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Stockholders' Equity Note [Abstract]
Anti-dilutive share-based awards	9	642

SHAREHOLDERS' EQUITY - Addition

SHAREHOLDERS' EQUITY - Additional Information (Detail) - USD ($) shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Aug. 31, 2017
Stockholders Equity Note [Line Items]
Common stock, share repurchase, dollar amount	$ 296	$ 610
Remaining common stock available for purchase under share repurchase authorizations	91.4
Share Repurchase Program
Stockholders Equity Note [Line Items]
Stock acquired in open market, shares	6.6	17
Common stock, share repurchase, dollar amount	$ 296	$ 600
Share Repurchase Authorization 2017
Stockholders Equity Note [Line Items]
Stock Repurchase Program, Number of Shares Authorized to be Repurchased			80

SHAREHOLDERS' EQUITY - Changes

SHAREHOLDERS' EQUITY - Changes in Accumulated Other Comprehensive Income (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2018		Mar. 31, 2017
Accumulated Other Comprehensive Income [Roll Forward]
Balance, beginning of period	[1]	$ 4,028		$ 2,630
Other comprehensive income loss before reclassifications net of tax	[1]	(571)		(10)
Amounts reclassified from accumulated other comprehensive income net of tax	[1]	228		12
Other comprehensive income (loss), net of tax	[1]	(343)		2
Balance, end of period	[1]	3,685		2,632
Unrealized foreign currency translation gains (losses)
Accumulated Other Comprehensive Income [Roll Forward]
Balance, beginning of period	[1]	(1,750)		(1,983)
Other comprehensive income loss before reclassifications net of tax	[1]	447		333
Amounts reclassified from accumulated other comprehensive income net of tax	[1]	0		0
Other comprehensive income (loss), net of tax	[1]	447		333
Balance, end of period	[1]	(1,303)		(1,650)
Unrealized gains (losses) on investment securities
Accumulated Other Comprehensive Income [Roll Forward]
Balance, beginning of period	[1]	5,964		4,805
Other comprehensive income loss before reclassifications net of tax	[1]	(983)		(341)
Amounts reclassified from accumulated other comprehensive income net of tax	[1]	225	[2]	10
Other comprehensive income (loss), net of tax	[1]	(758)		(331)
Balance, end of period	[1]	5,206		4,474
Unrealized gains (losses) on derivatives
Accumulated Other Comprehensive Income [Roll Forward]
Balance, beginning of period	[1]	(23)		(24)
Other comprehensive income loss before reclassifications net of tax	[1]	2		2
Amounts reclassified from accumulated other comprehensive income net of tax	[1]	0		0
Other comprehensive income (loss), net of tax	[1]	2		2
Balance, end of period	[1]	(21)		(22)
Pension liability adjustment
Accumulated Other Comprehensive Income [Roll Forward]
Balance, beginning of period	[1]	(163)		(168)
Other comprehensive income loss before reclassifications net of tax	[1]	(37)		(4)
Amounts reclassified from accumulated other comprehensive income net of tax	[1]	3		2
Other comprehensive income (loss), net of tax	[1]	(34)		(2)
Balance, end of period	[1]	(197)		(170)
Accounting Standards Update 2016-01 | Accumulated other comprehensive income (loss)
Accumulated Other Comprehensive Income [Roll Forward]
Cumulative effect of change in accounting principle, net of income taxes	[3]	(148)		0
Accounting Standards Update 2018-02 | Accumulated other comprehensive income (loss)
Accumulated Other Comprehensive Income [Roll Forward]
Cumulative effect of change in accounting principle, net of income taxes	[3]	$ 374		$ 0
[1]	All amounts in the table above are net of tax.
[2]	Includes amounts reclassified due to changes in accounting principles of $(148) related to financial instruments and $374 related to tax effects from tax reform
[3]	See Note 1 of the Notes to the Consolidated Financial Statements for the adoption of accounting guidance on January 1, 2018.

SHAREHOLDERS' EQUITY - Reclassi

SHAREHOLDERS' EQUITY - Reclassifications Out of Accumulated Other Comprehensive Income (Details) - USD ($) $ in Millions		1 Months Ended	3 Months Ended				12 Months Ended
		Jan. 31, 2018	Mar. 31, 2018		Mar. 31, 2017		Dec. 31, 2017
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other than temporary impairment losses realized			$ (7)		$ (10)
Total before tax			982		898
Income tax (expense) or benefit			(265)		(306)
Net of tax			$ 717		$ 592
Blended statutory income tax rate			27.00%
Statutory U.S. tax rate		21.00%	21.00%		35.00%		35.00%
Reclassification Out Of Accumulated Other Comprehensive Income
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net of tax			$ (2)		$ (12)
Reclassification Out Of Accumulated Other Comprehensive Income | Unrealized gains (losses) on investment securities
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Sales and redemptions			2		(6)
Other than temporary impairment losses realized			0		(10)
Total before tax			2		(16)
Income tax (expense) or benefit			(1)	[1]	6	[2]
Net of tax			1		(10)
Reclassification Out Of Accumulated Other Comprehensive Income | Pension liability adjustment
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Acquisition and operating expenses, actuarial gains (losses)	[3]		(4)		(3)
Acquisition and operating expenses, prior service (cost) credit	[3]		0		0
Income tax (expense) or benefit			1	[1]	1	[2]
Net of tax			$ (3)		$ (2)
[1]	Based on 27% blended tax rate
[2]	Based on 35% tax rate
[3]	These accumulated other comprehensive income components are included in the computation of net periodic pension cost (see Note 12 for additional details)

SHARE-BASED COMPENSATION - Addi

SHARE-BASED COMPENSATION - Additional Information (Detail) - USD ($) shares in Thousands, $ in Millions	1 Months Ended	3 Months Ended
	Feb. 28, 2018	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Proceeds from stock options exercised		$ 23	$ 17
Tax benefit from exercise of stock options		$ 12	$ 14
Long-Term Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation arrangement by share-based payment award, maximum number of shares issuable		75,000
Share-based compensation arrangement by share-based payment award, maximum number of shares issuable other than options and stock appreciation rights		38,000
Shares available for future grants under the long-term incentive plan		40,500
Long-term incentive plan awards, term (in years)		10 years
Long-term incentive plan awards, vesting period		3 years
Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total compensation cost not yet recognized, restricted stock awards		$ 62
Share-based compensation arrangement by share-based payment award, equity instruments other than options, nonvested, number, shares		3,517		3,635
Employee service share-based compensation, nonvested awards, compensation cost not yet recognized, period for recognition		1 year 6 months
Restricted stock awards, grants in period		918
Performance based Vesting Condition | Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total compensation cost not yet recognized, restricted stock awards		$ 30
Share-based compensation arrangement by share-based payment award, equity instruments other than options, nonvested, number, shares		826
Restricted stock awards, grants in period	432

SHARE-BASED COMPENSATION - Stoc

SHARE-BASED COMPENSATION - Stock Options Outstanding and Exercisable (Detail) $ / shares in Units, shares in Thousands, $ in Millions	3 Months Ended
	Mar. 31, 2018USD ($)$ / sharesshares
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Options Outstanding - Stock Option Shares | shares	6,306
Options Outstanding - Weighted-Average Remaining Term (Yrs)	5 years 6 months
Options Outstanding - Aggregate Intrinsic Value | $	$ 99
Options Outstanding - Weighted-Average Exercise Price Per Share | $ / shares	$ 28.03
Options Exercisable - Stock Option Shares | shares	4,439
Options Exercisable - Weighted-Average Remaining Term (Yrs.)	4 years 4 months 24 days
Options Exercisable - Aggregate Intrinsic Value | $	$ 77
Options Exercisable - Weighted-Average Exercise Price Per Share | $ / shares	$ 26.45

SHARE-BASED COMPENSATION - Rest

SHARE-BASED COMPENSATION - Restricted Stock Activity (Details) - Restricted Stock shares in Thousands	3 Months Ended
	Mar. 31, 2018$ / sharesshares
Shares
Beginning Balance | shares	3,635
Granted | shares	918
Canceled | shares	(56)
Vested | shares	(980)
Ending Balance | shares	3,517
Weighted-Average Grant-Date Fair Value Per Share
Beginning Balance | $ / shares	$ 32.40
Granted | $ / shares	44.12
Cancelled | $ / shares	33.18
Vested | $ / shares	31.50
Ending Balance | $ / shares	$ 35.70

BENEFIT PLANS - Additional Info

BENEFIT PLANS - Additional Information (Detail) - USD ($)	1 Months Ended	3 Months Ended		12 Months Ended
	Jan. 31, 2018	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2013
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Net periodic (benefit) cost, excluding service cost		$ 5,000,000	$ 5,000,000
Amount of years active employees have left to meet rule of 80 in order to be eligible for postretirement medical benefits				5 years
Amount of years left to meet 15 year service requirement for active employees age 55 or older to be eligible for postretirement medical benefits				5 years
Defined Contribution Plan, Special Contribution, Per Employee	$ 500
Percentage of matching contributions by the Company to employee's contributions to 401(k) plan	100.00%
Lower Limit
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Health care plan, retirement age and years of service combined years for eligibility (rule of 80)				80 years
Health care plan, retirement age for eligibility, (in years)				55 years
Health care plan, number of years of service for eligibility				15 years
Upper Limit
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Percentage of matching contributions by the Company to employee's contributions to 401(k) plan	4.00%
Japan | Pension Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Employer contributions		6,000,000
U.S. | Pension Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Employer contributions		$ 10,000,000

BENEFIT PLANS - Net Periodic (B

BENEFIT PLANS - Net Periodic (Benefit) Cost Included in Acquisition and Operating Expenses (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Other Postretirement Benefit Plans, Defined Benefit
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	$ 0	$ 0
Interest cost	0	0
Expected return on plan assets	0	0
Amortization of net actuarial loss	0	0
Amortization of prior service cost (credit)	0	0
Net periodic (benefit) cost	0	0
Japan | Pension Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	5	5
Interest cost	2	1
Expected return on plan assets	(2)	(1)
Amortization of net actuarial loss	0	0
Amortization of prior service cost (credit)	0	0
Net periodic (benefit) cost	5	5
U.S. | Pension Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	7	6
Interest cost	9	8
Expected return on plan assets	(7)	(6)
Amortization of net actuarial loss	4	3
Amortization of prior service cost (credit)	0	0
Net periodic (benefit) cost	$ 13	$ 11

COMMITMENTS AND CONTINGENT LI84

COMMITMENTS AND CONTINGENT LIABILITIES - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Commitments And Contingencies Disclosure [Line Items]
Loss contingency accrual, insurance-related assessment, discount rate		4.25%
Loss contingency, discounted amount of insurance-related assessment liability		$ 62
Loss contingency, undiscounted amount of insurance-related assessment liability		94
Loss contingency, insurance-related assessment, discounted amount of premium tax offset		48
Loss contingency, insurance-related assessment, undiscounted amount of premium tax offset		74
Loss contingency, loss in period		$ 14
Loss contingency, discounted amount of insurance-related assessment liability, realization period for associated asset offsets (in years)	4