Segments of Business - Schedule of Segment Information (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Mar. 31, 2021	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2021	Mar. 31, 2020	Mar. 31, 2019
Segment revenues (1)
Revenues	$ 59,142	$ 62,599	$ 60,808	$ 55,679	$ 58,535	$ 59,172	$ 57,616	$ 55,728	$ 238,228	$ 231,051	$ 214,319
Operating profit
Operating income									3,828	2,366	1,513
Corporate Expenses, Net									(8,645)	(973)	(639)
Interest expense									(217)	(249)	(264)
Income (loss) from continuing operations before income taxes									(5,034)	1,144	610
Depreciation and amortization
Total									887	922	949
Expenditures for long-lived assets
Total									641	506	557
Corporate
Operating profit
Operating income									0	(1,113)	(104)
Depreciation and amortization
Total									125	136	122
Expenditures for long-lived assets
Total									104	120	125
U.S. Pharmaceutical
Segment revenues (1)
Revenues									189,274	181,700	166,189
U.S. Pharmaceutical | Operating Segments
Operating profit
Operating income									2,763	2,745	2,710
Depreciation and amortization
Total									211	208	227
Expenditures for long-lived assets
Total									246	109	103
International
Segment revenues (1)
Revenues									35,965	38,341	38,023
International | Operating Segments
Operating profit
Operating income									(37)	(161)	(1,903)
Depreciation and amortization
Total									334	357	392
Expenditures for long-lived assets
Total									212	218	199
Medical-Surgical Solutions
Segment revenues (1)
Revenues									10,099	8,305	7,618
Medical-Surgical Solutions | Operating Segments
Operating profit
Operating income									707	499	455
Depreciation and amortization
Total									130	136	118
Expenditures for long-lived assets
Total									57	36	116
Prescription Technology Solutions
Segment revenues (1)
Revenues									2,890	2,705	2,489
Prescription Technology Solutions | Operating Segments
Operating profit
Operating income									395	396	355
Depreciation and amortization
Total									87	85	90
Expenditures for long-lived assets
Total									$ 22	$ 23	$ 14