Segment Information - Additional Information (Detail) (USD $)	3 Months Ended	9 Months Ended
Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014 Segment	Sep. 30, 2013
Segment Reporting [Abstract]
Number of reportable segments			3
Member co-share amounts and government subsidies	$ 2,600,000,000	$ 2,000,000,000	$ 6,800,000,000	$ 5,200,000,000
Depreciation and amortization classified as benefit expense	$ 27,000,000	$ 23,000,000	$ 79,000,000	$ 69,000,000

Depreciation and amortization expense that has been reclassified to be included with benefit expenses. The reclassification is the result of depreciation and amortization expense associated primarily from the delivery of pharmacy services by our wholly-owned pharmacy business included in our Healthcare Services segment.

No definition available.

Name:	hum_DepreciationAndAmortizationClassifiedAsBenefitExpense
Namespace Prefix:	hum_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration