BASIS OF PRESENTATION - Additional Information (Detail) (New TRICARE South Region Contract, USD $) In Millions, unless otherwise specified	3 Months Ended
Jun. 30, 2012
New TRICARE South Region Contract
Organization, Consolidation and Presentation of Financial Statements Disclosure [Line Items]
TRICARE Health care cost payments	$ 515
TRICARE Health care cost reimbursements	459
Difference between TRICARE health care costs payments and reimbursements	$ 56

The difference between health care cost payments and reimbursements related to the TRICARE South Region contract.

No definition available.

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