Common and Preferred Stock (Details) - $ / shares		12 Months Ended
	Dec. 31, 2018	Dec. 31, 2019	Dec. 20, 2018	Dec. 31, 2017
Common: Par value $.01 ($.25, Old Cigna), 600,000,000 shares authorized
Outstanding - beginning balance		380,924,000	0
Shares issued in connection with acquisition	137,337,000
Issued for stock option exercises and other benefit plans	91,000	3,413,000
Repurchase of common stock	(289,000)	(11,806,000)
Exchange of old Cigna shares for shares of Cigna	243,785,000
Outstanding - ending balance	380,924,000	372,531,000		0
Treasury stock	570,000	13,012,000
Issued - December 31	381,494,000	385,543,000
Common Stock, par value and shares authorized
Common stock, par value per share	$ 0.01	$ 0.01
Common stock shares authorized	600,000,000	600,000,000
Preferred Stock [Abstract]
Preferred Stock, Shares Authorized	25,000,000	25,000,000
Preferred Stock, Par Value Per Share	$ 1	$ 1
Preferred Stock, Shares Outstanding	0	0
Express Scripts Holding Company [Member]
Cash consideration per share			$ 48.75
Per share exchange ratio			0.2434
Common: Par value $.01 ($.25, Old Cigna), 600,000,000 shares authorized
Outstanding - beginning balance	564,300,000
Outstanding - ending balance			564,300,000
Old Cigna [Member]
Common: Par value $.01 ($.25, Old Cigna), 600,000,000 shares authorized
Outstanding - beginning balance	243,785,000	0	243,967,000	256,869,000
Issued for stock option exercises and other benefit plans			1,118,000	2,761,000
Repurchase of common stock			(1,300,000)	(15,663,000)
Exchange of old Cigna shares for shares of Cigna	(243,785,000)
Outstanding - ending balance	0		243,785,000	243,967,000
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
Issued - December 31	0			296,145,000
Common Stock, par value and shares authorized
Common stock, par value per share				$ 0.25
Common stock shares authorized				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