| Document and Entity Information | Aug. 08, 2019 |
| Cover [Abstract] | |
| Entity Registrant Name | HUMANA INC |
| Amendment Flag | false |
| Entity Central Index Key | 0000049071 |
| Document Type | 8-K |
| Document Period End Date | Aug. 8, 2019 |
| Entity Incorporation State Country Code | DE |
| Entity File Number | 1-5975 |
| Entity Tax Identification Number | 61-0647538 |
| Entity Address, Address Line One | 500 West Main Street |
| Entity Address, City or Town | Louisville |
| Entity Address, State or Province | KY |
| Entity Address, Postal Zip Code | 40202 |
| City Area Code | (502) |
| Local Phone Number | 580-1000 |
| Written Communications | false |
| Soliciting Material | false |
| Pre Commencement Tender Offer | false |
| Pre Commencement Issuer Tender Offer | false |
| Security 12b Title | Common Stock |
| Trading Symbol | HUM |
| Security Exchange Name | NYSE |
| Entity Emerging Growth Company | false |
