Consolidated Statements of Changes in Total Equity - USD ($) $ in Millions	Total	Previously Reported [Member]	Restatement Adjustment [Member]	Shareholders' Equity [Member]	Shareholders' Equity [Member] Previously Reported [Member]	Shareholders' Equity [Member] Restatement Adjustment [Member]	Common Stock [Member]	Common Stock [Member] Previously Reported [Member]	Additional Paid In Capital [Member]	Additional Paid In Capital [Member] Previously Reported [Member]	Accumulated Other Comprehensive Income [Member]	Accumulated Other Comprehensive Income [Member] Previously Reported [Member]	Retained Earnings [Member]	Retained Earnings [Member] Previously Reported [Member]	Retained Earnings [Member] Restatement Adjustment [Member]	Treasury Stock [Member]	Treasury Stock [Member] Previously Reported [Member]	Other noncontrolling interests [Member]	Other noncontrolling interests [Member] Previously Reported [Member]
Total Equity, beginning of period at Dec. 31, 2015	$ 12,020	$ 12,044	$ (24)	$ 12,011	$ 12,035	$ (24)	$ 74	$ 74	$ 2,859	$ 2,859	$ (1,250)	$ (1,250)	$ 12,097	$ 12,121	$ (24)	$ (1,769)	$ (1,769)	$ 9	$ 9
Increase (Decrease) In Stockholders Equity [Roll Forward]
Effect of issuing stock for employee benefit plans	91			91					51				(123)			163
Other comprehensive income (loss)	(132)			(132)							(132)							0
Net income (loss)	1,850			1,867									1,867					(17)
Common dividends declared (per share: $0.04)	(10)			(10)									(10)
Repurchase of common stock	(110)			(110)												(110)
Other transactions impacting noncontrolling interest	(6)			(18)					(18)									12
Total Equity, end of period at Dec. 31, 2016	13,703			13,699			74		2,892		(1,382)		13,831			(1,716)		4
Beginning Balance at Dec. 31, 2015	69	$ 69
Redeemable Noncontrolling Interests
Other comprehensive income (loss)	(10)
Net income (loss)	(7)
Other transactions impacting noncontrolling interest	6
Ending Balance at Dec. 31, 2016	58
Increase (Decrease) In Stockholders Equity [Roll Forward]
Effect of issuing stock for employee benefit plans	248			248					51				(258)			455
Other comprehensive income (loss)	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
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
Exchange of Old Cigna common stock	0			0			(58)		58
Acquisition of Express Scripts (see Note 3)	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)	(390)			(390)							(390)
Net income (loss)	2,637			2,637									2,637					0
Common dividends declared (per share: $0.04)	(10)			(10)									(10)
Repurchase of common stock	(329)			(329)												(329)
Retirement of treasury stock	0			0			(13)		(529)				(3,498)			4,040
Other transactions impacting noncontrolling interest	0			0					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