Segments of Business (Details) numberOfProducts in Thousands, $ in Millions	3 Months Ended			6 Months Ended
	Sep. 30, 2020 USD ($) numberOfSegments country numberOfProducts	Sep. 30, 2019 USD ($)	Jun. 30, 2019 USD ($)	Sep. 30, 2020 USD ($) country numberOfProducts	Sep. 30, 2019 USD ($)
Segment Reporting Information [Line Items]
Number of reportable segments | numberOfSegments	4
Segment revenues
Total revenues	$ 60,808	$ 57,616		$ 116,487	$ 113,344
Segment operating profit (loss)
Total operating profit (loss)	634	626		1,312	1,260
Corporate income (expenses), net	(148)	(350)		(216)	(511)
Interest expense	(50)	(64)		(110)	(120)
Income (loss) from continuing operations before income taxes	655	(970)		1,300	(351)
Pre-tax credits related to LIFO accounting				104	48
Restructuring, impairment, and related charges	60	45		116	68
Goodwill impairment charge	69	0		69	0
Proportionate loss from investment in Change Healthcare	0	1,454		0	1,450
Joint Venture
Segment operating profit (loss)
Pre-tax dilution loss		246			246
Joint Venture | Change Healthcare JV
Segment operating profit (loss)
Impairment		1,200			1,200
Proportionate loss from investment in Change Healthcare		51			47
United States | Pension Plan
Segment operating profit (loss)
Pre-tax settlement expense		105	$ 17		122
In re: National Prescription Opioid Litigation
Segment operating profit (loss)
Corporate income (expenses), net				131
Charge in connection with State of New York's Opioid Stewardship Act	50			50
Opioid-related settlement charges		82			82
Pre-tax litigation expense	$ 41	36		84	72
United States
Segment Reporting Information [Line Items]
Number of reportable segments | numberOfSegments	3
Operating Segments
Segment operating profit (loss)
Total operating profit (loss)	$ 853	(556)		1,626	280
Corporate
Segment operating profit (loss)
Total operating profit (loss)	0	(1,454)		0	(1,450)
Restructuring, impairment, and related charges	12	27		40	44
U.S. Pharmaceutical
Segment operating profit (loss)
Pre-tax credits related to LIFO accounting	52	33		104	48
Goodwill impairment charge				0
U.S. Pharmaceutical | Operating Segments
Segment revenues
Total revenues	48,067	45,613		92,737	89,402
Segment operating profit (loss)
Total operating profit (loss)	623	641		$ 1,236	$ 1,217
Revenue derived from services, percentage (less than)				1.00%	1.00%
Restructuring, impairment, and related charges	10	3		$ 12	$ 2
International
Segment operating profit (loss)
Goodwill impairment charge	69			69
After-tax goodwill impairment	69			69
International | Strategic Growth Initiative Plan
Segment operating profit (loss)
Restructuring, impairment, and related charges	$ 27			$ 41
International | Europe
Segment Reporting Information [Line Items]
Number of countries in which entity segment operates | country	13			13
International | Operating Segments
Segment revenues
Total revenues	$ 9,540	9,321		$ 18,092	18,728
Segment operating profit (loss)
Total operating profit (loss)	(45)	30		$ (42)	$ 61
Revenue derived from services, percentage (less than)				6.00%	6.00%
Restructuring, impairment, and related charges	$ 35	12		$ 58	$ 16
Medical-Surgical Solutions
Segment Reporting Information [Line Items]
Number of national brand medical-surgical products offered (more than) | numberOfProducts	275			275
Segment operating profit (loss)
Goodwill impairment charge				$ 0
Medical-Surgical Solutions | Operating Segments
Segment revenues
Total revenues	$ 2,533	2,056		4,334	3,959
Segment operating profit (loss)
Total operating profit (loss)	187	129		$ 276	$ 254
Revenue derived from services, percentage (less than)				2.00%	2.00%
Restructuring, impairment, and related charges	3	3		$ 6	$ 6
Prescription Technology Solutions | Operating Segments
Segment revenues
Total revenues	668	626		1,324	1,255
Segment operating profit (loss)
Total operating profit (loss)	88	98		$ 156	$ 198
Revenue derived from services, percentage (less than)				40.00%	40.00%
Restructuring, impairment, and related charges	$ 0	$ 0		$ 0	$ 0