Schedule Summarizing Quarterly Operation Results (Parenthetical) (Detail) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended	12 Months Ended
Dec. 31, 2013	Dec. 31, 2013	Dec. 31, 2012
Quarterly Financial Information Disclosure [Abstract]
Charge related to closed block of long-term care policies	$ 243	$ 243	$ 29
After tax impact of charge	$ 154hum_AfterTaxImpactOfCharge
Impact on EPS of charge	$ 0.99hum_ImpactOnEPSOfCharge

Charge related to closed block of long-term care policies

No definition available.

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