Fair Value Measurements - Not Carried at Fair Value (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
Mar. 31, 2014	Dec. 31, 2013
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Commercial Mortgage Loans	$ 2,125	$ 2,252
Percentage of contractholder deposit funds that can be withdrawn at any time	60.00%
Estimate Of Fair Value Fair Value Disclosure [Member] \| Fair Value Inputs Level 2 [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Long-term debt, including current maturities, excluding capital leases	5,629	5,550
Estimate Of Fair Value Fair Value Disclosure [Member] \| Fair Value Inputs Level 3 [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Commercial Mortgage Loans	2,222	2,338
Contractholder deposit funds, excluding universal life products	1,131	1,081
Carrying Reported Amount Fair Value Disclosure [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Commercial Mortgage Loans	2,125	2,252
Contractholder deposit funds, excluding universal life products	1,119	1,072
Long-term debt, including current maturities, excluding capital leases	$ 4,981	$ 4,997

The liability as of the balance sheet date to the policyholders for deposits held under the terms of insurance contracts. This excludes universal life products.

No definition available.

+ Details

Name:	ci_ContractholderDepositFundsExcludingUniversalLifeProducts
Namespace Prefix:	ci_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Percent of contractholder deposit funds, excluding universal life product that can be withdrawn by the customer at any time without prior notice or penalty.

+ References

No definition available.

+ Details

Name:	ci_PercentUnrestrictedContractholderDepositFunds
Namespace Prefix:	ci_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The fair value amount of long-term debt whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission.

+ References

No definition available.

+ Details

Name:	us-gaap_LongTermDebtFairValue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The balance represents the amount of loans that are secured by real estate mortgages, offset by the reserve to cover probable credit losses on the loan portfolio.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.7-03.1(c))

-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 1

-Subparagraph c

-Article 7

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant