Reinsurance - Reinsurance Recoverables (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Ceded Credit Risk [Line Items]
Reinsurance recoverables	$ 7,098us-gaap_ReinsuranceRecoverables	$ 7,080us-gaap_ReinsuranceRecoverables
Reserve netted against reinsurance recoverables	4
Minimum [Member] \| Standard Poors A Rating Or Better [Member]
Ceded Credit Risk [Line Items]
Reinsurance recoverable percent secured	90.00%
Guaranteed Minimum Income Benefit [Member]
Ceded Credit Risk [Line Items]
Number of external reinsurers	3	3
Berkshire Hathway Life Insurance Company Of Nebraska [Member] \| Guaranteed Minimum Death Benefits [Member]
Ceded Credit Risk [Line Items]
Reinsurance recoverables	1,125	1,147
Berkshire Hathway Life Insurance Company Of Nebraska [Member] \| Guaranteed Minimum Death Benefits [Member] \| Ceded Credit Risk Secured [Member]
Ceded Credit Risk [Line Items]
Reinsurance recoverables percentage of total	100.00%
The Lincoln National Life Insurance Company And Lincoln Life And Annuity Of New York [Member] \| Individual Life Insurance And Annuity [Member]
Ceded Credit Risk [Line Items]
Reinsurance recoverables	3,846	3,817
Prudential Retirement Insurance And Annuity Company [Member] \| Retirement Benefits [Member]
Ceded Credit Risk [Line Items]
Reinsurance recoverables	1,070	1,092
Prudential Retirement Insurance And Annuity Company [Member] \| Retirement Benefits [Member] \| Ceded Credit Risk Secured [Member]
Ceded Credit Risk [Line Items]
Reinsurance recoverables percentage of total	100.00%
Great American Life Insurance Company [Member] \| Supplemental Benefits business (resulting from the acquistion) [Member]
Ceded Credit Risk [Line Items]
Reinsurance recoverables	331	336
Great American Life Insurance Company [Member] \| Supplemental Benefits business (resulting from the acquistion) [Member] \| Ceded Credit Risk Secured [Member]
Ceded Credit Risk [Line Items]
Reinsurance recoverables percentage of total	99.00%
Other Retrocessionaires [Member] \| Guaranteed Minimum Death Benefits [Member]
Ceded Credit Risk [Line Items]
Reinsurance recoverables	38	39
Other Retrocessionaires [Member] \| Guaranteed Minimum Death Benefits [Member] \| Ceded Credit Risk Secured [Member]
Ceded Credit Risk [Line Items]
Reinsurance recoverables percentage of total	99.00%
Other Retrocessionaires [Member] \| Ongoing Operations [Member]
Ceded Credit Risk [Line Items]
Reinsurance recoverables	600	561
Maximum reinsurance recoverable from a single reinsurer	191
Other Retrocessionaires [Member] \| Ongoing Operations [Member] \| Maximum [Member]
Ceded Credit Risk [Line Items]
Minimum reinsurance recoverable balance from a single reinsurer	1
Other Retrocessionaires [Member] \| Ongoing Operations [Member] \| Minimum [Member]
Ceded Credit Risk [Line Items]
Number of external reinsurers	80
Other Retrocessionaires [Member] \| Ongoing Operations [Member] \| Ceded Credit Risk Secured [Member]
Ceded Credit Risk [Line Items]
Reinsurance recoverables percentage of total	9.00%
Other Retrocessionaires [Member] \| Other run-off reinsurance [Member]
Ceded Credit Risk [Line Items]
Reinsurance recoverables	$ 88	$ 88
Other Retrocessionaires [Member] \| Other run-off reinsurance [Member] \| Ceded Credit Risk Secured [Member]
Ceded Credit Risk [Line Items]
Reinsurance recoverables percentage of total	100.00%

The number of external reinsurers underwriting credit risk ceded by the Company.

No definition available.

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- Definition

The carrying value as of the balance sheet date of the estimated valuation allowance to reduce gross reinsurance premiums receivable to net realizable value.

+ References

No definition available.

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Out of a specified group or category, the maximum reinsurance recoverable from a single reinsurer.

+ References

No definition available.

+ Details

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

- Definition

Percentage of reinsurance recoverables secured by assets in trust or letters of credit.

+ References

No definition available.

+ Details

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- Definition

Out of a specified group or category, the minimum reinsurance recoverable balance from a single reinsurer.

+ References

No definition available.

+ Details

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- Details

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Period Type:	duration

- Definition

Amount after valuation allowance recoverable including premium paid under reinsurance contracts. Examples include, but are not limited to, settled and unsettled claims, incurred but not reported losses, loss adjustment expense, premium paid, policy benefits and policy reserves.

+ References

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 6

-Article 7

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 20

-Section 50

-Paragraph 5

-URI http://asc.fasb.org/extlink&oid=6480758&loc=d3e6824-158387

Reference 3: 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.(a),6)

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

+ Details

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- Definition

Percentage of total reinsurance recoverables.

+ References

No definition available.

+ Details

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- Details

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- Details

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- Details

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- Details

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- Details

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- Details

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