Mergers and Acquisitions (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Business Combinations [Abstract]
Integration and transaction-related costs, pre-tax	$ 130	$ 155	$ 227	$ 291
Integration and transaction-related costs, after-tax	$ 99	$ 115	$ 173	$ 223

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