Document and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2021	Feb. 23, 2022	Jun. 30, 2021
Entity Information [Line Items]
Document Type	10-K
Document Annual Report	true
Amendment Flag	false
Document Period End Date	Dec. 31, 2021
Document Fiscal Year Focus	2021
Current Fiscal Year End Date	--12-31
Document Fiscal Period Focus	FY
Document Transition Report	false
Entity File Number	001-11294
Entity Registrant Name	Unum Group
Entity Central Index Key	0000005513
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	62-1598430
Entity Address, Address Line One	1 Fountain Square
Entity Address, City or Town	Chattanooga,
Entity Address, State or Province	TN
Entity Address, Postal Zip Code	37402
City Area Code	423
Local Phone Number	294-1011
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
ICFR Auditor Attestation Flag	true
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		202,563,754
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Public Float			$ 5,800,000,000
Auditor Firm ID	42
Auditor Name	Ernst & Young LLP
Auditor Location	Chattanooga, Tennessee
NEW YORK STOCK EXCHANGE, INC. | Common Class A
Entity Information [Line Items]
Title of 12(b) Security	Common stock, $0.10 par value
Trading Symbol	UNM
Security Exchange Name	NYSE
NEW YORK STOCK EXCHANGE, INC. | 6.250% Junior Subordinated Notes due 2058
Entity Information [Line Items]
Title of 12(b) Security	6.250% Junior Subordinated Notes due 2058
Trading Symbol	UNMA
Security Exchange Name	NYSE