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Segments of Business - Schedule of Reportable Operating Segment (Details) $ in Millions	3 Months Ended			9 Months Ended
	Dec. 31, 2024 USD ($) segment	Dec. 31, 2023 USD ($)	Sep. 30, 2023 USD ($)	Dec. 31, 2024 USD ($) segment	Dec. 31, 2023 USD ($)
Segment revenues
Total revenues	$ 95,294	$ 80,898		$ 268,228	$ 232,596
Segment operating profit (loss)
Total operating profit (loss)	1,224	642		2,831	2,693
Subtotal	1,453	879		3,576	3,362
Corporate expenses, net	(160)	(203)		(512)	(571)
Interest expense	(67)	(64)		(220)	(172)
Income before income taxes	1,226	612		$ 2,844	2,619
Number of reportable segments | segment				4
Accounts receivable, credit loss expense (reversal)				$ (144)	780
Proceeds from legal settlements	31
Pre-tax credits related to LIFO accounting				85	89
Restructuring, impairment, and related charges, net	32	4		276	84
Income (loss) from equity method investments				(43)
Gains (losses) associated with equity investments	$ 6	0		101	0
Rx Savings Solutions, LLC
Segment operating profit (loss)
Fair value adjustment gain		2			78
United States
Segment operating profit (loss)
Number of reportable segments | segment	3
Corporate
Segment operating profit (loss)
Restructuring, impairment, and related charges, net	$ 10	4		34	50
Gains (losses) associated with equity investments				101
Corporate | Canadian retail disposal group
Segment operating profit (loss)
Other comprehensive loss	12			62
Corporate | National Prescription Opioid Litigation
Segment operating profit (loss)
Pre-tax expenses related to estimated litigation liability				51
U.S. Pharmaceutical
Segment revenues
Total revenues	87,110	73,023		244,551	209,949
Segment operating profit (loss)
Total operating profit (loss)	854	307		2,710	1,727
Accounts receivable, credit loss expense (reversal)		515	$ 210	203	725
Proceeds from legal settlements	31	23		184	220
U.S. Pharmaceutical | Operating Segments
Segment operating profit (loss)
Pre-tax credits related to LIFO accounting	89	2		85	89
Restructuring, impairment, and related charges, net	2	(5)		67	6
U.S. Pharmaceutical | Operating Segments | National Prescription Opioid Litigation
Segment operating profit (loss)
Pre-tax expenses related to estimated litigation liability				57
Prescription Technology Solutions
Segment revenues
Total revenues	1,371	1,205		3,877	3,589
Segment operating profit (loss)
Total operating profit (loss)	219	178		627	647
Prescription Technology Solutions | Operating Segments
Segment operating profit (loss)
Restructuring, impairment, and related charges, net	0	2		5	7
Medical-Surgical Solutions
Segment revenues
Total revenues	2,949	3,031		8,533	8,476
Segment operating profit (loss)
Total operating profit (loss)	269	268		546	739
Medical-Surgical Solutions | Operating Segments
Segment operating profit (loss)
Restructuring, impairment, and related charges, net	19	3		169	9
International
Segment revenues
Total revenues	3,860	3,639		11,260	10,582
Segment operating profit (loss)
Total operating profit (loss)	111	126		(307)	249
International | Canadian retail disposal group | Held-for-sale
Segment operating profit (loss)
Canadian businesses held for sale	11			604
International | Operating Segments
Segment operating profit (loss)
Restructuring, impairment, and related charges, net	1	0		1	12
Corporate
Segment revenues
Total revenues	$ 4	$ 0		$ 7	$ 0
Revenue from Contract with Customer, Product and Service Benchmark | Product Concentration Risk | U.S. Pharmaceutical
Segment operating profit (loss)
Revenue derived from services, percentage (approximately or less than)	1.00%
Revenue from Contract with Customer, Product and Service Benchmark | Product Concentration Risk | Prescription Technology Solutions
Segment operating profit (loss)
Revenue derived from services, percentage (approximately or less than)	38.00%
Revenue from Contract with Customer, Product and Service Benchmark | Product Concentration Risk | Medical-Surgical Solutions
Segment operating profit (loss)
Revenue derived from services, percentage (approximately or less than)	1.00%
Revenue from Contract with Customer, Product and Service Benchmark | Product Concentration Risk | International
Segment operating profit (loss)
Revenue derived from services, percentage (approximately or less than)	1.00%

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