Segment Information Deferred Acquisition Costs by Segment (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Movement Analysis of Deferred Policy Acquisition Costs [Roll Forward]
Deferred Acquisition Costs at Beginning of Period	$ 1,755.5	$ 1,677.1	$ 1,816.1
Deferral of Acquisition Costs	466.8	467.3	442.5
Deferred Policy Acquisition Cost, Amortization Expense	(418.9)	(378.7)	(365.7)
Impairment of Deferred Acquisition Costs	0	0	(196.0)
Adjustment Related to Unrealized Investment Gain (Loss)	25.4	(12.0)	(19.6)
Deferred Policy Acquisition Costs Foreign Currency Translation Adjustment And Other	(0.4)	(1.8)	(0.2)
Deferred Acquisition Costs at End of Period	1,829.2	1,755.5	1,677.1
Unum U.S.
Movement Analysis of Deferred Policy Acquisition Costs [Roll Forward]
Deferred Acquisition Costs at Beginning of Period	1,024.3	971.8	943.7
Deferral of Acquisition Costs	252.0	249.2	220.3
Deferred Policy Acquisition Cost, Amortization Expense	(230.0)	(196.5)	(188.1)
Impairment of Deferred Acquisition Costs			0
Adjustment Related to Unrealized Investment Gain (Loss)	5.2	(0.2)	(4.1)
Deferred Policy Acquisition Costs Foreign Currency Translation Adjustment And Other	0	0	0
Deferred Acquisition Costs at End of Period	1,051.5	1,024.3	971.8
Unum U.K.
Movement Analysis of Deferred Policy Acquisition Costs [Roll Forward]
Deferred Acquisition Costs at Beginning of Period	38.8	40.9	41.0
Deferral of Acquisition Costs	9.8	11.8	15.4
Deferred Policy Acquisition Cost, Amortization Expense	(14.7)	(15.7)	(15.3)
Impairment of Deferred Acquisition Costs			0
Adjustment Related to Unrealized Investment Gain (Loss)	0	0	0
Deferred Policy Acquisition Costs Foreign Currency Translation Adjustment And Other	(0.4)	(1.8)	(0.2)
Deferred Acquisition Costs at End of Period	34.3	38.8	40.9
Colonial Life
Movement Analysis of Deferred Policy Acquisition Costs [Roll Forward]
Deferred Acquisition Costs at Beginning of Period	692.4	664.4	628.0
Deferral of Acquisition Costs	205.0	206.3	203.1
Deferred Policy Acquisition Cost, Amortization Expense	(174.2)	(166.5)	(151.2)
Impairment of Deferred Acquisition Costs			0
Adjustment Related to Unrealized Investment Gain (Loss)	20.2	(11.8)	(15.5)
Deferred Policy Acquisition Costs Foreign Currency Translation Adjustment And Other	0	0	0
Deferred Acquisition Costs at End of Period	743.4	692.4	664.4
Closed Block
Movement Analysis of Deferred Policy Acquisition Costs [Roll Forward]
Deferred Acquisition Costs at Beginning of Period	0	0	203.4
Deferral of Acquisition Costs	0	0	3.7
Deferred Policy Acquisition Cost, Amortization Expense	0	0	(11.1)
Impairment of Deferred Acquisition Costs			(196.0)
Adjustment Related to Unrealized Investment Gain (Loss)	0	0	0
Deferred Policy Acquisition Costs Foreign Currency Translation Adjustment And Other	0	0	0
Deferred Acquisition Costs at End of Period	$ 0	$ 0	$ 0