| Document and Entity Information Document | Jun. 15, 2020 |
| Document Type | 8-K |
| Document Period End Date | Jun. 15, 2020 |
| Entity Central Index Key | 0000004977 |
| Entity Registrant Name | Aflac Incorporated |
| Entity Incorporation, State or Country Code | GA |
| Entity File Number | 001-07434 |
| 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 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Entity Emerging Growth Company | false |
| Amendment Flag | false |
| NEW YORK STOCK EXCHANGE, INC. | |
| Title of 12(b) Security | Common Stock, $.10 Par Value |
| Trading Symbol | AFL |
| Security Exchange Name | NYSE |
