Investment Securities - Additional Information (Detail) (USD $)	12 Months Ended
Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Schedule of Available-for-sale Securities [Line Items]
Percentage of debt securities considered to be of investment-grade	94.00%
Percentage of tax-exempt municipal securities classified as pre-refunded	10.00%
General obligation bonds as percentage of tax-exempt municipal securities that were not pre-refunded	40.00%
Special revenue bonds as percentage of tax exempt municipal securities that were not pre-refunded	60.00%
Maximum percentage of any general obligation bonds in one state	11.00%
Percentage of tax-exempt securities insured by bond insurers	20.00%
Residential and commercial mortgage-backed securities, percentage of collateral consisting of prime loans	99.00%
Percentage of corporate securities associated with financial services industry	22.80%	19.30%
Other-than-temporary impairments	$ 0	$ 0	$ 0

General Obligation Bonds As Percentage Of Tax Exempt Municipal Securities That Were Not Pre Refunded

No definition available.

Name:	hum_GeneralObligationBondsAsPercentageOfTaxExemptMunicipalSecuritiesThatWereNotPreRefunded
Namespace Prefix:	hum_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Maximum percentage of any general obligation bonds in one state

+ References

No definition available.

+ Details

Name:	hum_MaximumPercentageOfAnyGeneralObligationBondsInOneState
Namespace Prefix:	hum_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage of collateral related to prime loans

+ References

No definition available.

+ Details

Name:	hum_PercentageOfCollateralRelatedToPrimeLoan
Namespace Prefix:	hum_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Percentage of corporate securities associated with financial services industry.

+ References

No definition available.

+ Details

Name:	hum_PercentageOfCorporateSecuritiesAssociatedWithFinancialServicesIndustry
Namespace Prefix:	hum_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Percentage of tax exempt securities

+ References

No definition available.

+ Details

Name:	hum_PercentageOfTaxExemptSecurities
Namespace Prefix:	hum_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Percentage Of tax-exempt to municipal securities classified as pre-refunded

+ References

No definition available.

+ Details

Name:	hum_PercentageOfTaxExemptToMunicipalSecuritiesClassifiedAsPreRefunded
Namespace Prefix:	hum_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Percentage of Total Debt Securities

+ References

No definition available.

+ Details

Name:	hum_PercentageOfTotalDebtSecurities
Namespace Prefix:	hum_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Special Revenue Bonds As Percentage Of Tax Exempt Municipal Securities That Were Not Pre Refunded

+ References

No definition available.

+ Details

Name:	hum_SpecialRevenueBondsAsPercentageOfTaxExemptMunicipalSecuritiesThatWereNotPreRefunded
Namespace Prefix:	hum_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

The amount by which the fair value of an investment is less than the amortized cost basis or carrying amount of that investment at the balance sheet date and the decline in fair value is deemed to be other than temporary, before considering whether or not such amount is recognized in earnings or other comprehensive income.

+ References

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

-Publisher FASB

-Name FASB Staff Position (FSP)

-Number FAS115-1/124-1

-Paragraph 15C

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 35

-Paragraph 34

-URI http://asc.fasb.org/extlink&oid=16383099&loc=d3e25351-111560

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 115

-Paragraph 16

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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

-Publisher FASB

-Name FASB Staff Position (FSP)

-Number FAS115-1/124-1

-Paragraph 16B

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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

-Publisher FASB

-Name FASB Staff Position (FSP)

-Number FAS115-1/124-1

-Paragraph 15D

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 6: 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=6943989&loc=d3e3602-108585

Reference 7: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name FASB Staff Position (FSP)

-Number FAS115-2/124-2

-Paragraph 22

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

+ Details

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

- Details

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