Document and Entity Information - $ / shares	3 Months Ended
	Mar. 31, 2018	Apr. 20, 2018	Dec. 31, 2017
Document Document And Entity Information [Abstract]
Document Type	10-Q
Document Period End Date	Mar. 31, 2018
Entity Registrant Name	CIGNA Corporation
Entity Central Index Key	0000701221
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Trading Symbol	CI
Entity Common Stock Shares Outstanding		243,268,191
Amendment Flag	false
Entity Current Reporting Status	Yes
Entity Well Known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Document Fiscal Year Focus	2018
Document Fiscal Period Focus	Q1
Common stock, par value per share	$ 0.25		$ 0.25