Fair Value Measurements - Measured Under Certain Conditions (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
Mar. 31, 2014	Mar. 31, 2013
Financing Receivable, Impaired [Line Items]
Realized investment losses on impaired commercial mortgage loans and real estate entities	$ 4	$ 0
Maximum [Member]
Financing Receivable, Impaired [Line Items]
Impaired commercial mortgage loans and real estate entities as a percent of total investments	1.00%	0.00%

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

No definition available.

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