Consolidated Statements of Changes in Total Equity - USD ($) $ in Millions	Total	Shareholders' Equity [Member]	Common Stock [Member]	Additional Paid In Capital [Member]	Accumulated Other Comprehensive Income [Member]	Retained Earnings [Member]	Treasury Stock [Member]	Other noncontrolling interests [Member]
Total Equity, beginning of period at Dec. 31, 2016	$ 13,703	$ 13,699	$ 74	$ 2,892	$ (1,382)	$ 13,831	$ (1,716)	$ 4
Increase (Decrease) In Stockholders Equity [Roll Forward]
Effect of issuing stock for employee benefit plans	248	248		51		(258)	455
Other comprehensive income (loss), net of tax	300	300			300
Net income (loss)	2,232	2,237				2,237		(5)
Common dividends declared (per share: $0.04)	(10)	(10)				(10)
Repurchase of common stock	(2,760)	(2,760)					(2,760)
Other transactions impacting noncontrolling interest	(2)	(3)		(3)				1
Total Equity, end of period at Dec. 31, 2017	13,711	13,711	74	2,940	(1,082)	15,800	(4,021)	0
Beginning Balance at Dec. 31, 2016	58
Redeemable Noncontrolling Interests
Other comprehensive income (loss)	(3)
Net income (loss)	0
Other transactions impacting noncontrolling interest	(6)
Ending Balance at Dec. 31, 2017	49
Increase (Decrease) In Stockholders Equity [Roll Forward]
Reclassification adjustment related to U.S. tax reform legislation	0	0			(229)	229
Retirement of treasury stock	0	0	(13)	(529)		(3,498)	4,040
Exchange of Old Cigna common stock	0	0	(58)	58
Acquisition of Express Scripts (see Note 4)	25,231	25,224	1	25,223				7
Effect of issuing stock for employee benefit plans	127	127		59		(138)	206
Other comprehensive income (loss), net of tax	(390)	(390)			(390)
Net income (loss)	2,637	2,637				2,637
Common dividends declared (per share: $0.04)	(10)	(10)				(10)
Repurchase of common stock	(329)	(329)					(329)
Other transactions impacting noncontrolling interest	0	0
Total Equity, end of period at Dec. 31, 2018	41,035	41,028	4	27,751	(1,711)	15,088	(104)	7
Redeemable Noncontrolling Interests
Other comprehensive income (loss)	(15)
Net income (loss)	9
Other transactions impacting noncontrolling interest	(6)
Ending Balance at Dec. 31, 2018	37
Increase (Decrease) In Stockholders Equity [Roll Forward]
Effect of issuing stock for employee benefit plans	451	451		555			(104)
Other comprehensive income (loss), net of tax	770	770			770
Net income (loss)	5,109	5,104				5,104		5
Common dividends declared (per share: $0.04)	(15)	(15)				(15)
Repurchase of common stock	(1,985)	(1,985)					(1,985)
Other transactions impacting noncontrolling interest	(6)	0						(6)
Total Equity, end of period at Dec. 31, 2019	45,344	$ 45,338	$ 4	$ 28,306	$ (941)	$ 20,162	$ (2,193)	$ 6
Redeemable Noncontrolling Interests
Other comprehensive income (loss)	(5)
Net income (loss)	11
Other transactions impacting noncontrolling interest	(8)
Ending Balance at Dec. 31, 2019	$ 35