Contingencies and Other Matters - Guarantees (Details) $ in Millions	6 Months Ended
Jun. 30, 2016 USD ($)
Financial Guarantee [Member] \| Retirement And Life Insurance Contracts [Member]
Guarantee Obligations [Line Items]
Guarantee Obligations, Maximum Exposure, Undiscounted	$ 492
Guarantee Obligations, Current Carrying Value	$ 0
Percentage of benefit obligations reinsured	14.00%
Financial Guarantee [Member] \| Retirement And Life Insurance Contracts [Member] \| Minimum [Member]
Guarantee Obligations [Line Items]
Assets maintained by employers to cover benefit obligations	$ 492
Guarantee Type, Other [Member] \| Variable Annuity [Member] \| Guaranteed Minimum Income Benefit [Member]
Guarantee Obligations [Line Items]
Guarantee Obligations, Maximum Exposure, Undiscounted	$ 804
Annuitization election period	30 days
Underlying mutual fund investment values	$ 879
Guarantee Type, Other [Member] \| Variable Annuity [Member] \| Guaranteed Minimum Income Benefit [Member] \| Minimum [Member]
Guarantee Obligations [Line Items]
Guarantee Obligations, Current Carrying Value	804
Indemnification obligations to lenders [Member]
Guarantee Obligations [Line Items]
Guarantee Obligations, Maximum Exposure, Undiscounted	184
Guarantee Obligations, Current Carrying Value	$ 0
Indemnification obligations in connection with acquistion, disposition and reinsurance transactions [Member]
Guarantee Obligations [Line Items]
Guarantee Obligations, Maximum Exposure Inestimable	The Company does not believe that it is possible to determine the maximum potential amount due under these obligations, because not all amounts due under these indemnification obligations are subject to limitation.
Guarantee Obligations, Current Carrying Value	$ 0
Market Value Guarantee [Member]
Guarantee Obligations [Line Items]
Guarantee Obligations, Maximum Exposure, Undiscounted	41
Guarantee Obligations, Current Carrying Value	16
Expiring In 2016 [Member]
Guarantee Obligations [Line Items]
Guarantee Obligations, Maximum Exposure, Undiscounted	16
Expiring In 2022 [Member]
Guarantee Obligations [Line Items]
Guarantee Obligations, Maximum Exposure, Undiscounted	$ 25

The period of time prior to a policy anniversary when an annuitization election must occur.

No definition available.

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- Definition

The percentage of separate account assets associated with the sold retirement benefits business that represent the fair value of contract holder funds guaranteed by the Company.

+ References

No definition available.

+ Details

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Period Type:	instant

- Definition

The value of investments in mutual funds assumed in calculating the reporting entity's maximum potential future payments for guarantees related to reinsured benefits.

+ References

No definition available.

+ Details

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Namespace Prefix:	ci_
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Balance Type:	debit
Period Type:	instant

- Definition

The current carrying amount of the liability for the freestanding or embedded guarantor's obligations under the guarantee or each group of similar guarantees.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 460
-SubTopic 10
-Section 50
-Paragraph 4
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=6851643&loc=d3e12069-110248

+ Details

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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- Definition

Indicates, if estimable, the approximate extent to which the proceeds from liquidation of any assets held either as collateral or by third parties would be expected to cover the maximum potential amount of future payments under the guarantee or each group of similar guarantees.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 460
-SubTopic 10
-Section 50
-Paragraph 4
-Subparagraph (f)
-URI http://asc.fasb.org/extlink&oid=6851643&loc=d3e12069-110248

+ Details

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Period Type:	duration

- Definition

Maximum potential amount of future payments (undiscounted) the guarantor could be required to make under the guarantee or each group of similar guarantees before reduction for potential recoveries under recourse or collateralization provisions.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 460
-SubTopic 10
-Section 50
-Paragraph 4
-Subparagraph (b)(1)
-URI http://asc.fasb.org/extlink&oid=6851643&loc=d3e12069-110248

+ Details

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- Definition

States the reasons why the guarantor is unable to develop an estimate of the maximum potential amount of future payments under its guarantee (or each group of similar guarantees).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 460
-SubTopic 10
-Section 50
-Paragraph 4
-Subparagraph (b)(3)
-URI http://asc.fasb.org/extlink&oid=6851643&loc=d3e12069-110248

+ 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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- Details

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- Details

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