Segments of Business (Details) $ in Millions, $ in Millions			3 Months Ended			6 Months Ended
	May 23, 2018 USD ($)	May 23, 2018 CAD ($)	Sep. 30, 2019 USD ($) country	Jun. 30, 2019 USD ($)	Sep. 30, 2018 USD ($)	Sep. 30, 2019 USD ($) segment country	Sep. 30, 2018 USD ($)
Segment Reporting Information [Line Items]
Number of reportable segments | segment						3
Revenues
Total Revenues			$ 57,616		$ 53,075	$ 113,344	$ 105,682
Operating profit
Total operating profit			626		689	1,260	772
Corporate Expenses, Net			(364)		(167)	(539)	(290)
Interest Expense			(64)		(66)	(120)	(127)
Income (Loss) from Continuing Operations Before Income Taxes			(970)		587	(351)	593
Pre-tax credits related to LIFO accounting						48	43
Proceeds from legal settlements							35
Pretax goodwill impairment charges			0		0	0	570
Net restructuring charges recognized			45		82	68	178
Net restructuring charges recognized, after tax			35		67	52	152
Loss from investment in Change Healthcare Joint Venture			1,454		56	1,450	112
U.S. Pharmaceutical and Specialty Solutions
Operating profit
Pre-tax credits related to LIFO accounting			$ 33		22	$ 48	43
European Pharmaceutical Solutions
Segment Reporting Information [Line Items]
Number of countries in which entity segment operates | country			13			13
Operating profit
Pretax goodwill impairment charges							570
After-tax goodwill impairment							570
Operating Segments
Revenues
Total Revenues			$ 57,616		53,075	$ 113,344	105,682
Operating profit
Total operating profit			(542)		820	308	1,010
Operating Segments | U.S. Pharmaceutical and Specialty Solutions
Revenues
Total Revenues			45,979		41,610	90,144	82,587
Operating profit
Total operating profit			$ 639		$ 610	$ 1,218	$ 1,153
Revenue derived from services, percentage (less than)			1.00%		1.00%	1.00%	1.00%
Operating Segments | European Pharmaceutical Solutions
Revenues
Total Revenues			$ 6,598		$ 6,639	$ 13,308	$ 13,574
Operating profit
Total operating profit			$ 1		$ 10	$ 6	$ (550)
Revenue derived from services, percentage (less than)			10.00%		10.00%	10.00%	10.00%
Operating Segments | Medical-Surgical Solutions
Revenues
Total Revenues			$ 2,056		$ 1,948	$ 3,959	$ 3,651
Operating profit
Total operating profit			$ 129		$ 105	$ 254	$ 198
Revenue derived from services, percentage (less than)			2.00%		2.00%	2.00%	2.00%
Operating Segments | Other
Revenues
Total Revenues			$ 2,983		$ 2,878	$ 5,933	$ 5,870
Operating profit
Total operating profit			(1,311)		95	(1,170)	209
Joint Venture
Operating profit
Pre-tax credit recognized on relief from potential future obligations					90		90
Pre-tax dilution loss from reduction of ownership			(246)
After-tax dilution loss from reduction of ownership			(184)
Gain on escrow settlement							66
Joint Venture | Change Healthcare JV
Operating profit
Pre-tax impairment charge			1,157
Loss from investment in Change Healthcare Joint Venture			51		56	47	112
United States
Revenues
Total Revenues			48,292		43,774	94,614	86,664
Foreign
Revenues
Total Revenues			9,324		9,301	18,730	19,018
Canada | Other
Operating profit
Net restructuring charges recognized					42		80
Third Party Seller of Rexall Health | Rexall Health | Canada
Operating profit
Escrow settlement gain, pre-tax	$ 97	$ 125					97
Escrow settlement gain, net of tax							97
United States | Pension Plan
Operating profit
Pre-tax settlement expense			105			122
After-tax settlement expense			78	$ 12
Pre-tax litigation and other-related expenses			36		$ 43	72	$ 59
In re: National Prescription Opioid Litigation
Operating profit
Pre-tax litigation and other-related expenses						(82)
After-tax litigation and other-related expenses			$ (82)			$ (82)