Segment Information - Retrospective Adjustment (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Total revenues	$ 61,646	$ 45,743
Revenues	61,397	45,693
Cost of products sold	37,247	37,505
Benefit Costs	13,459	1,329
Operating expenses	8,250	4,913
Operating income	2,690	1,996
Adjusted Operating Income (Loss)	3,595	2,293
Corporate / Other [Member]
Total revenues	110	48
Pharmacy Services Segment [Member]
Total revenues	33,558	32,546
Revenues	33,558	32,546
Retail Long-Term Care Segment [Member]
Total revenues	21,115	20,432
Health Care Benefits Segment [Member]
Total revenues	17,870	1,318
Intersegment Eliminations [Member]
Total revenues	(11,007)	(8,601)
Revenues	(11,007)	(8,601)
Cost of products sold		(8,318)
Benefit Costs		0
Operating expenses		(108)
Operating income		(175)
Adjusted Operating Income (Loss)	(172)	(175)
Operating Segments [Member] | Corporate / Other [Member]
Total revenues	110	48
Revenues	25	0
Cost of products sold		0
Benefit Costs		0
Operating expenses		264
Operating income		(216)
Adjusted Operating Income (Loss)	(231)	(218)
Operating Segments [Member] | Pharmacy Services Segment [Member]
Total revenues	33,558	32,546
Revenues	33,558	32,546
Cost of products sold		31,307
Benefit Costs		0
Operating expenses		338
Operating income		901
Adjusted Operating Income (Loss)	947	987
Operating Segments [Member] | Retail Long-Term Care Segment [Member]
Total revenues	21,115	20,432
Revenues	21,115	20,432
Cost of products sold		14,516
Benefit Costs		0
Operating expenses		4,292
Operating income		1,624
Adjusted Operating Income (Loss)	1,489	1,836
Operating Segments [Member] | Health Care Benefits Segment [Member]
Total revenues	17,870	1,318
Revenues	17,706	1,316
Cost of products sold		0
Benefit Costs		1,329
Operating expenses		127
Operating income		(138)
Adjusted Operating Income (Loss)	$ 1,562	(137)
Previously Reported [Member]
Total revenues		45,743
Cost of products sold		37,505
Benefit Costs		1,329
Operating expenses		4,913
Operating income		1,996
Previously Reported [Member] | Intersegment Eliminations [Member]
Total revenues		(6,957)
Cost of products sold		(6,762)
Benefit Costs		0
Operating expenses		(20)
Operating income		(175)
Previously Reported [Member] | Operating Segments [Member] | Corporate / Other [Member]
Total revenues		48
Cost of products sold		0
Benefit Costs		0
Operating expenses		264
Operating income		(216)
Previously Reported [Member] | Operating Segments [Member] | Pharmacy Services Segment [Member]
Total revenues		32,220
Cost of products sold		29,751
Benefit Costs		1,329
Operating expenses		377
Operating income		763
Previously Reported [Member] | Operating Segments [Member] | Retail Long-Term Care Segment [Member]
Total revenues		20,432
Cost of products sold		14,516
Benefit Costs		0
Operating expenses		4,292
Operating income		1,624
Previously Reported [Member] | Operating Segments [Member] | Health Care Benefits Segment [Member]
Total revenues		0
Cost of products sold		0
Benefit Costs		0
Operating expenses		0
Operating income		0
Restatement Adjustment [Member]
Total revenues		0
Cost of products sold		0
Benefit Costs		0
Operating expenses		0
Operating income		0
Adjusted Operating Income (Loss)		297
Restatement Adjustment [Member] | Intersegment Eliminations [Member]
Total revenues		(1,644)
Cost of products sold		(1,556)
Benefit Costs		0
Operating expenses		(88)
Operating income		0
Adjusted Operating Income (Loss)		0
Restatement Adjustment [Member] | Operating Segments [Member] | Corporate / Other [Member]
Total revenues		0
Cost of products sold		0
Benefit Costs		0
Operating expenses		0
Operating income		0
Adjusted Operating Income (Loss)		(2)
Restatement Adjustment [Member] | Operating Segments [Member] | Pharmacy Services Segment [Member]
Total revenues		326
Cost of products sold		1,556
Benefit Costs		(1,329)
Operating expenses		(39)
Operating income		138
Adjusted Operating Income (Loss)		86
Restatement Adjustment [Member] | Operating Segments [Member] | Retail Long-Term Care Segment [Member]
Total revenues		0
Cost of products sold		0
Benefit Costs		0
Operating expenses		0
Operating income		0
Adjusted Operating Income (Loss)		212
Restatement Adjustment [Member] | Operating Segments [Member] | Health Care Benefits Segment [Member]
Total revenues		1,318
Cost of products sold		0
Benefit Costs		1,329
Operating expenses		127
Operating income		(138)
Adjusted Operating Income (Loss)		$ 1