Mergers and Acquistions (Details) $ / shares in Units, $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2016 USD ($) $ / shares	Jun. 30, 2016 USD ($) $ / shares	Jul. 28, 2016 $ / shares
Acquisitions and Dispositions [Abstract]
Cash consideration for each share of Company stock \| $ / shares	$ 103.40	$ 103.40
Shares of acquirer common stock for each share of Company stock	0.5152	0.5152
Closing price of Anthem common stock \| $ / shares			$ 132.90
Termination fee payable to Company	$ 1,850	$ 1,850
Merger-related costs	34	74
Merger-related costs, after-tax	$ 26	$ 62

Stock consideration per share of acquirer to company shareholders under the proposed merger agreement.

No definition available.

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- Definition

Merger agreement termination fee due from acquirer to the Company if regulatory approval is not attained or if closing does not occur by January 31, 2017 (subject to extension to April 30, 2017 under certain circumstances).

+ References

No definition available.

+ Details

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Data Type:	xbrli:monetaryItemType
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Period Type:	instant

- Definition

This element represents after-tax acquisition-related costs incurred to effect a business combination which costs have been expensed during the period. Such costs include finder's fees; advisory, legal, accounting, valuation, and other professional or consulting fees; general administrative costs, including the costs of maintaining an internal acquisitions department; and may include costs of registering and issuing debt and equity securities.

+ References

No definition available.

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Cash consideration per share to company stockholders under the proposed merger agreement.

+ References

No definition available.

+ Details

Name:	ci_CashConsiderationPerShareToCompanyStockholdersUnderMergerAgreement
Namespace Prefix:	ci_
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- Definition

Closing price of Anthem, Inc. common stock

+ References

No definition available.

+ Details

Name:	ci_SharePriceAnthem
Namespace Prefix:	ci_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	instant

- Definition

This element represents acquisition-related costs incurred to effect a business combination which costs have been expensed during the period. Such costs include finder's fees; advisory, legal, accounting, valuation, and other professional or consulting fees; general administrative costs, including the costs of maintaining an internal acquisitions department; and may include costs of registering and issuing debt and equity securities.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 25
-Paragraph 23
-URI http://asc.fasb.org/extlink&oid=34752592&loc=d3e1043-128460

+ Details

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- References

No definition available.

+ Details

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