Liability for Unpaid Claims - Additional Information (Detail) $ in Millions	12 Months Ended
Dec. 31, 2015 USD ($)
Closed Block \| Long-term Care
Liability for Unpaid Claims and CAE Narrative Information
Reserve Increase for Long-term Care, Before Tax	$ 698.2
Claim Reserve Prior Year
Liability for Unpaid Claims and CAE Narrative Information
Reserve Increase for Long-term Care, Before Tax	$ 85.8

Reserve Increase for Long-term Care, Before Tax - This amount represents the special item long-term care reserve charge.

No definition available.

Name:	unm_ReserveIncreaseforLongtermCareBeforeTax
Namespace Prefix:	unm_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration