Earnings (Loss) Per Common Share - Schedule of Basic and Diluted Earnings per Common Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	12 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Mar. 31, 2022
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Income from continuing operations	$ 3,160	$ 3,725	$ 1,292
Net income attributable to noncontrolling interests	(158)	(162)	(173)
Income from continuing operations attributable to McKesson Corporation	3,002	3,563	1,119
Loss from discontinued operations, net of tax	0	(3)	(5)
Net income attributable to McKesson Corporation	$ 3,002	$ 3,560	$ 1,114
Weighted-average common shares outstanding:
Basic (in shares)	133.2	141.1	152.3
Diluted (in shares)	134.1	142.2	154.1
Diluted
Continuing operations (in dollars per share)	$ 22.39	$ 25.05	$ 7.26
Discontinued operations (in dollars per share)	0	(0.02)	(0.03)
Total (in dollars per share)	22.39	25.03	7.23
Basic
Continuing operations (in dollars per share)	22.54	25.25	7.35
Discontinued operations (in dollars per share)	0	(0.02)	(0.03)
Total (in dollars per share)	$ 22.54	$ 25.23	$ 7.32
Stock options
Weighted-average common shares outstanding:
Effect of dilutive securities (in shares)	0.2	0.2	0.2
Restricted stock unit awards
Weighted-average common shares outstanding:
Effect of dilutive securities (in shares)	0.7	0.9	1.6