Recent Accounting Pronouncements - Guidance Not Yet Adopted (Details) $ in Millions	Sep. 30, 2016 USD ($)
Restatement Adjustment [Member] \| Accounting Standards Update 2016-01 [Member] \| Retained Earnings [Member]
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Impact of new guidance on equity if adopted	$ 60

Amount of cumulative effect of the change in accounting principle or new accounting pronouncement on retained earnings or other components of equity or net assets in the statement of financial position if implemented as of the implementation date.

No definition available.

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