Document and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2020	Feb. 17, 2021	Jun. 30, 2020
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2020
Document Transition Report	false
Entity File Number	001-07434
Entity Registrant Name	Aflac Incorporated
Entity Incorporation, State or Country Code	GA
Entity Tax Identification Number	58-1167100
Entity Address, Address Line One	1932 Wynnton Road
Entity Address, City or Town	Columbus
Entity Address, State or Province	GA
Entity Address, Postal Zip Code	31999
City Area Code	706
Local Phone Number	323.3431
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Public Float			$ 25,577,863,783
Entity Common Stock, Shares Outstanding		688,587,083
Amendment Flag	false
Entity Central Index Key	0000004977
Current Fiscal Year End Date	--12-31
Document Fiscal Period Focus	FY
Document Fiscal Year Focus	2020
ICFR Auditor Attestation Flag	true
Documents Incorporated by Reference	Certain information contained in the Notice and Proxy Statement for the Company’s 2021 Annual Meeting of Shareholders is incorporated by reference into Part III hereof.
NEW YORK STOCK EXCHANGE, INC.
Title of 12(b) Security	Common Stock, $.10 Par Value
Trading Symbol	AFL
Security Exchange Name	NYSE