Operating Revenue

No definition available.

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

- Definition

The aggregate expense recognized in the current period that allocates the cost of tangible assets, intangible assets, or depleting assets to periods that benefit from use of the assets.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 28

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585

+ Details

Name:	us-gaap_DepreciationDepletionAndAmortization
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Interest and debt related expenses associated with nonoperating financing activities of the entity.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 835

-SubTopic 20

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6450988&loc=d3e26243-108391

+ Details

Name:	us-gaap_InterestAndDebtExpense
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount, after investment expense, of income earned from investments in securities and real estate. Includes, but is not limited to, real estate investment, policy loans, dividends, and interest. Excludes realized gain (loss) on investments.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 16

-Article 12

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 225

-Section S99

-Paragraph 1

-Subparagraph (SX 210.7-04.2)

-URI http://asc.fasb.org/extlink&oid=6879464&loc=d3e573970-122913

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 04

-Paragraph 2

-Article 7

+ Details

Name:	us-gaap_NetInvestmentIncome
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The net result for the period of deducting operating expenses from operating revenues.

+ References

No definition available.

+ Details

Name:	us-gaap_OperatingIncomeLoss
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Reflects the sum of all other revenue and income recognized by the entity in the period not otherwise specified in the income statement.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 225

-Section S99

-Paragraph 1

-Subparagraph (SX 210.7-04.4)

-URI http://asc.fasb.org/extlink&oid=6879464&loc=d3e573970-122913

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 04

-Paragraph 4

-Article 7

+ Details

Name:	us-gaap_OtherIncome
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount, after premiums ceded to other entities and premiums assumed by the entity, of premiums earned.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 17

-Article 12

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 235

-Section S99

-Paragraph 2

-Subparagraph (SX 210.12-17)

-URI http://asc.fasb.org/extlink&oid=34713774&loc=d3e574992-122915

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 225

-Section S99

-Paragraph 1

-Subparagraph (SX 210.7-04.1)

-URI http://asc.fasb.org/extlink&oid=6879464&loc=d3e573970-122913

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 04

-Paragraph 1

-Article 7

Reference 5: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 605

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6486672&loc=d3e27261-158547

Reference 6: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 225

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-04.13(c))

-URI http://asc.fasb.org/extlink&oid=6879574&loc=d3e536633-122882

+ Details

Name:	us-gaap_PremiumsEarnedNet
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Details

Name:	us-gaap_SegmentReportingInformationLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_ConsolidationItemsAxis=us-gaap_OperatingSegmentsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Selected Operating Statement Data by Segment (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Segment Reporting Information
Premium Income	$ 1,967.9us-gaap_PremiumsEarnedNet	$ 1,947.2us-gaap_PremiumsEarnedNet	$ 1,943.6us-gaap_PremiumsEarnedNet	$ 1,938.5us-gaap_PremiumsEarnedNet	$ 1,890.7us-gaap_PremiumsEarnedNet	$ 1,897.3us-gaap_PremiumsEarnedNet	$ 1,905.8us-gaap_PremiumsEarnedNet	$ 1,930.9us-gaap_PremiumsEarnedNet	$ 7,797.2us-gaap_PremiumsEarnedNet	$ 7,624.7us-gaap_PremiumsEarnedNet	$ 7,716.1us-gaap_PremiumsEarnedNet
Net Investment Income	629.4us-gaap_NetInvestmentIncome	606.4us-gaap_NetInvestmentIncome	629.1us-gaap_NetInvestmentIncome	612.5us-gaap_NetInvestmentIncome	629.4us-gaap_NetInvestmentIncome	615.5us-gaap_NetInvestmentIncome	626.1us-gaap_NetInvestmentIncome	621.1us-gaap_NetInvestmentIncome	2,477.4us-gaap_NetInvestmentIncome	2,492.1us-gaap_NetInvestmentIncome	2,515.2us-gaap_NetInvestmentIncome
Other Income									219.0us-gaap_OtherIncome	230.2us-gaap_OtherIncome	227.9us-gaap_OtherIncome
Interest and Debt Expense									167.5us-gaap_InterestAndDebtExpense	149.4us-gaap_InterestAndDebtExpense	145.4us-gaap_InterestAndDebtExpense
Operating Segments
Segment Reporting Information
Premium Income									7,797.2	7,624.7	7,716.1
Net Investment Income									2,477.4	2,492.1	2,515.2
Other Income									219.0	230.2	227.9
Operating Revenue									10,493.6	10,347.0	10,459.2
Operating Income (Loss)									1,292.5	1,241.8	1,239.7
Interest and Debt Expense									154.3	149.4	145.4
Depreciation, Depletion and Amortization									534.4	509.8	468.5
Operating Segments \| Unum U.S.
Segment Reporting Information
Premium Income									4,659.7	4,517.1	4,456.5
Net Investment Income									890.3	929.6	952.3
Other Income									122.1	128.3	124.6
Operating Revenue									5,672.1	5,575.0	5,533.4
Operating Income (Loss)									856.3	859.0	847.1
Interest and Debt Expense									0	0.1	1.1
Depreciation, Depletion and Amortization									314.2	292.5	255.6
Operating Segments \| Unum U.K.
Segment Reporting Information
Premium Income									607.2	556.6	694.6
Net Investment Income									151.0	148.5	170.8
Other Income									0	0.1	0.1
Operating Revenue									758.2	705.2	865.5
Operating Income (Loss)									147.8	132.0	131.3
Interest and Debt Expense									0	0	0
Depreciation, Depletion and Amortization									19.2	22.5	27.2
Operating Segments \| Colonial Life
Segment Reporting Information
Premium Income									1,273.7	1,232.2	1,194.5
Net Investment Income									146.7	145.4	138.6
Other Income									0.1	0.2	0.3
Operating Revenue									1,420.5	1,377.8	1,333.4
Operating Income (Loss)									300.2	284.9	274.3
Interest and Debt Expense									0	0	0
Depreciation, Depletion and Amortization									194.1	188.7	181.0
Operating Segments \| Closed Block
Segment Reporting Information
Premium Income									1,256.6	1,318.8	1,370.5
Net Investment Income									1,284.1	1,272.3	1,230.5
Other Income									91.8	93.9	100.1
Operating Revenue									2,632.5	2,685.0	2,701.1
Operating Income (Loss)									122.6	109.4	95.5
Interest and Debt Expense									7.3	8.4	10.4
Depreciation, Depletion and Amortization									5.9	5.2	3.9
Operating Segments \| Corporate and Other Segment
Segment Reporting Information
Premium Income									0	0	0
Net Investment Income									5.3	(3.7)	23.0
Other Income									5.0	7.7	2.8
Operating Revenue									10.3	4.0	25.8
Operating Income (Loss)									(134.4)	(143.5)	(108.5)
Interest and Debt Expense									147.0	140.9	133.9
Depreciation, Depletion and Amortization									$ 1.0	$ 0.9	$ 0.8