Cover Page - USD ($)	12 Months Ended
	Dec. 31, 2019	Jan. 31, 2020	Jun. 30, 2019
Cover page.
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2019
Document Transition Report	false
Entity File Number	1-5975
Entity Registrant Name	HUMANA INC.
Entity Central Index Key	0000049071
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	FY
Amendment Flag	false
Entity Incorporation, State or Country Code	DE
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
Title of 12(b) Security	Common stock, $0.16 2/3 par value
Trading Symbol	HUM
Security Exchange Name	NYSE
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			$ 35,478,894,483
Entity Common Stock, Shares Outstanding		132,106,497
Documents Incorporated by Reference	Parts II and III incorporate herein by reference portions of the Registrant’s Proxy Statement to be filed pursuant to Regulation 14A with respect to the Annual Meeting of Stockholders scheduled to be held on April 23, 2020.