Investments - Problem and Potential Problem Commercial Mortgage Loans (Details) (Mortgage Loans on Real Estate [Member], USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013
Mortgage Loans on Real Estate [Member]
Financing Receivable, Modifications [Line Items]
Restructured problem loan, pre-modification		$ 31
Restructured problem loan, number of contracts		2
Restructured problem loan, post-modification		31
Restructured problem loan, required reserves		0
Restructured problem loan, number of contracts - post-modification		2
Maximum past due days that the mortgage loans are considered current	59 days
Debt service coverage ratio threshold, below which mortgage loans are considered potential problems	1.0
Loan-to-value ratio threshold, above which mortgage loans are considered potential problems	100.00%
Minimum past due days that mortgage loans are considered potential problems	30 days
Maximum past due days that mortgage loans are considered potential problems	60 days
Problem and potential problem mortgage loans	208	158
Loans modified but not considered troubled debt restructurings

Represents debt service coverage ratio threshold, below which mortgage loans are considered potential problems.

No definition available.

Name:	ci_DebtServiceCoverageRatioThresholdBelowWhichMortgageLoansAreConsideredPotentialProblems
Namespace Prefix:	ci_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	duration

- Definition

Number of financing receivables that have resulted from troubled debt restructurings.

+ References

No definition available.

+ Details

Name:	ci_FinancingReceivableModificationsNumberOfContractsPostmodification
Namespace Prefix:	ci_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Reflects the amount of loans modified during the reporting period other than troubled debt restructurings.

+ References

No definition available.

+ Details

Name:	ci_FinancingReceivablesModified
Namespace Prefix:	ci_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Represents loan-to-value ratio threshold, above which mortgage loans are considered potential problems.

+ References

No definition available.

+ Details

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

- Definition

Represents maximum period of time past due that the mortgage before classification of loans changes from potential problems to problem loans.

+ References

No definition available.

+ Details

Name:	ci_MaximumPeriodOfTimePastDueMortgageLoansAreConsideredPotentialProblems
Namespace Prefix:	ci_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents maximum period of time past due for classification of the mortgage loans as current.

+ References

No definition available.

+ Details

Name:	ci_MaximumPeriodOfTimePastDueThatMortgageLoansAreConsideredCurrent
Namespace Prefix:	ci_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the minimum period of time for principal and interest to be past due before classification of loans as potential problems.

+ References

No definition available.

+ Details

Name:	ci_MimimumPeriodOfTimePastDueThatMortgageLoansAreConsideredPotentialProblems
Namespace Prefix:	ci_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Problem And Potential Problem Mortgage Loans

+ References

No definition available.

+ Details

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

- Details

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

- Definition

Number of financing receivables that have been modified by troubled debt restructurings.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 50

-Paragraph 33

-URI http://asc.fasb.org/extlink&oid=28368275&loc=SL6953676-111524

+ Details

Name:	us-gaap_FinancingReceivableModificationsNumberOfContracts2
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Post-modification amount of investment in financing receivables modified by troubled debt restructurings.

+ References

+ Details

Name:	us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Pre-modification amount of investment in financing receivables modified by troubled debt restructurings.

+ References

+ Details

Name:	us-gaap_FinancingReceivableModificationsPreModificationRecordedInvestment2
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Reflects the amount of the write-down related to a troubled debt restructuring.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 40

-Section 50

-Paragraph 4

-URI http://asc.fasb.org/extlink&oid=25495931&loc=d3e18845-111554

+ Details

Name:	us-gaap_FinancingReceivablesImpairedTroubledDebtRestructuringWriteDown
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration