Fair Value Measurements - Level 2 Assets and Liabilities (Details)	3 Months Ended
Mar. 31, 2013
Fair Value Disclosures [Abstract]
Percent Level 2 Fixed Maturities Equity Securities	91.00%
Percent Level 2 Investments Foreign Bonds Broker Quote	Less than 1

Percentage of Level 2 investments representing foreign bonds priced using a single unadjusted market-observable input derived by averaging multiple broker-dealer quotes.

No definition available.

Name:	ci_PercentLevel2InvestmentsForeignBondsBrokerQuote
Namespace Prefix:	ci_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration