Common and Preferred Stock (Details) - $ / shares		12 Months Ended
	Dec. 31, 2018	Dec. 20, 2018	Dec. 31, 2017	Dec. 31, 2016
Common: Old Cigna - Par value $.25, 600,000,000 shares authorized; New Cigna - Par value $.01, 600,000,000 shares authorized
Outstanding - beginning balance		0	0
Shares issued in connection with acquisition	137,337,000
Issued for stock option exercises and other benefit plans	91,000
Repurchase of common stock	(289,000)
Exchange of old Cigna shares for shares of Cigna	243,785,000
Outstanding - ending balance	380,924,000		0	0
Treasury stock	570,000		0	0
Issued - December 31	381,494,000		296,145,000	0
Common Stock, par value and shares authorized
Common stock, par value per share	$ 0.01		$ 0.25
Common stock shares authorized	600,000,000		600,000,000
Preferred Stock [Abstract]
Preferred Stock, Shares Authorized	25,000,000
Preferred Stock, Par Value Per Share	$ 1
Preferred Stock, Shares Outstanding	0
Express Scripts Holding Company [Member]
Cash consideration per share		$ 48.75
Per share exchange ratio		0.2434
Common: Old Cigna - Par value $.25, 600,000,000 shares authorized; New Cigna - Par value $.01, 600,000,000 shares authorized
Outstanding - beginning balance	564,300,000
Outstanding - ending balance		564,300,000
Old Cigna [Member]
Common: Old Cigna - Par value $.25, 600,000,000 shares authorized; New Cigna - Par value $.01, 600,000,000 shares authorized
Outstanding - beginning balance	243,785,000	243,967,000	256,869,000	256,544,000
Issued for stock option exercises and other benefit plans		1,118,000	2,761,000	1,110,000
Repurchase of common stock		(1,300,000)	(15,663,000)	(785,000)
Exchange of old Cigna shares for shares of Cigna	(243,785,000)
Outstanding - ending balance	0	243,785,000	243,967,000	256,869,000
Retirement of treasury stock	(52,358,000)
Exchange of old Cigna certificated treasury stock for new Cigna certificated treasury stock	(2,000)
Treasury stock	0		52,178,000	39,276,000
Issued - December 31	0		296,145,000	296,145,000
Common Stock, par value and shares authorized
Common stock, par value per share		$ 0.25	$ 0.25	$ 0.25
Common stock shares authorized		600,000,000	600,000,000	600,000,000
Preferred Stock [Abstract]
Preferred Stock, Shares Authorized		25,000,000	25,000,000	25,000,000
Preferred Stock, Par Value Per Share		$ 1	$ 1	$ 1
Preferred Stock, Shares Outstanding		0	0	0