Unaudited Quarterly Results - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2013
Unaudited Quarterly Results - Additional Information [Abstract]
Unclaimed Death Benefit Reserve Increase Before Taxes	$ 95.5
Unclaimed Death Benefit Reserve Increase After Tax	62.1
Waiver of Premium Benefit Reserve Increase (Decrease) Before Tax	85.0
Waiver of Premium Benefit Reserve Decrease After Tax	$ 55.2

Unclaimed Death Benefit Reserve Increase (Decrease) - the before tax increase (decrease) adjustment to reserves for unclaimed death benefits as a result of searching the Death Master File.

No definition available.

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