Earnings (Loss) Per Common Share - Schedule of Computations for Basic and Diluted Earnings per Common Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended
	Jun. 30, 2022	Jun. 30, 2021
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Income from continuing operations	$ 807	$ 536
Net income attributable to noncontrolling interests	(41)	(47)
Income from continuing operations attributable to McKesson Corporation	766	489
Income (loss) from discontinued operations, net of tax	2	(3)
Net income attributable to McKesson Corporation	$ 768	$ 486
Weighted-average common shares outstanding:
Basic (in shares)	144.2	156.2
Effect of dilutive securities:
Diluted (in shares)	145.9	158.1
Diluted
Continuing operations (in usd per share)	$ 5.25	$ 3.09
Discontinued operations (in usd per share)	0.01	(0.02)
Total (in dollars per share)	5.26	3.07
Basic
Continuing operations (in usd per share)	5.31	3.13
Discontinued operations (in usd per share)	0.01	(0.02)
Total (in dollars per share)	$ 5.32	$ 3.11
Stock options
Effect of dilutive securities:
Restricted stock units (in shares)	0.3	0.1
Restricted stock units
Effect of dilutive securities:
Restricted stock units (in shares)	1.4	1.8