Name:	ci_AcquirerStockConsiderationPerShareToAcquireeStockholdersUnderMergerAgreement
Namespace Prefix:	ci_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

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

No definition available.

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

Fee the Company will be required to pay Express Scripts if the Merger Agreement is terminated (1) by Express Scripts because the board of directors of the Company has changed its recommendation prior to obtaining the required approval of the stockholders of the Company, (2) by Express Scripts or the Company if the board of directors of the Company has changed its recommendation and the stockholders of the Company have voted against adopting the Merger Agreement or (3) by the Company in order to enter into an alternative acquisition agreement with respect to a Parent Superior Proposal that did not result from a breach of the Company's non-solicitation obligations. Further, if the Merger Agreement is terminated under certain circumstances and within 12 months after the date of such termination the Company enters into an agreement regarding a sale of a majority of the Company's assets or equity or consummates such a sale, then the Company will be required to pay the Parent Termination Fee prior to or contemporaneously with such entry or consummation.

No definition available.

Name:	ci_ParentTerminationFeeExpressScriptsMerger
Namespace Prefix:	ci_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

A reverse termination fee the Company may be required to pay Express Scripts in the event that the Merger Agreement is terminated by either the Company or Express Scripts due to (1) a legal restraint relating to a regulatory law prohibiting consummation of the Merger having become final and non-appealable or (2) the Merger not having been consummated on or prior to December 8, 2018 (subject to an extension to June 8, 2019 if extended by the Company or Express Scripts under certain circumstances); and, in the case of clause (2), at the time of such termination, all of the conditions to the Company's obligation to consummate the Merger have been satisfied other than those that relate to the absence of a legal restraint relating to a regulatory law or the receipt of a regulatory approval.

No definition available.

Name:	ci_ReverseTerminationFeeExpressScriptsMerger
Namespace Prefix:	ci_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Termination fee payable to Company under specified circumstances.

No definition available.

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

Transaction-related costs primarily consisting of fees for legal, advisory and other professional services as well as employee costs.

No definition available.

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

After-tax transaction-related costs including the impact of tax benefits realized from termination of merger agreement. Transaction-related costs consist primarily of fees for legal, advisory and other professional services as well as employee costs.

No definition available.

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

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.

No definition available.