Fair Value Measurements - Measured Under Certain Conditions (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2013	Dec. 31, 2012
Financing Receivable, Impaired [Line Items]
Realized investment losses on impaired commercial mortage loans and partnership entities	$ 12	$ 7
Maximum [Member]
Financing Receivable, Impaired [Line Items]
Impaired commercial mortgage loans and partnership entities as a percent of total investments	1.00%	1.00%

The percentage of total investments represented by impaired commercial mortgage loans and partnership entities written down to fair value.

No definition available.

Name:	ci_PercentageOfImpairedCommercialMortgageLoansAndPartnershipEntitiesOfTotalInvestments
Namespace Prefix:	ci_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant