| Document and Entity Information | Sep. 23, 2019 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Amendment Flag | false |
| Document Period End Date | Sep. 23, 2019 |
| Entity Registrant Name | Humana Inc. |
| Entity Incorporation, State or Country Code | DE |
| Entity File Number | 001-05975 |
| Entity Tax Identification Number | 61-0647538 |
| Entity Address, Address Line One | 500 W. 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 |
| Entity Emerging Growth Company | false |
| Entity Central Index Key | 0000049071 |
