Earnings 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, 2022	Mar. 31, 2021	Mar. 31, 2020
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Income (loss) from continuing operations	$ 1,292	$ (4,339)	$ 1,126
Net income attributable to noncontrolling interests	(173)	(199)	(220)
Income (loss) from continuing operations attributable to McKesson	1,119	(4,538)	906
Loss from discontinued operations, net of tax	(5)	(1)	(6)
Net income (loss) attributable to McKesson Corporation	$ 1,114	$ (4,539)	$ 900
Weighted-average common shares outstanding:
Basic (in shares)	152.3	160.6	180.6
Effect of dilutive securities (in shares)	1.6	0.0	1.0
Diluted (in shares)	154.1	160.6	181.6
Diluted
Continuing operations (in dollars per share)	$ 7.26	$ (28.26)	$ 4.99
Discontinued operations (in dollars per share)	(0.03)	0	(0.04)
Total (in dollars per share)	7.23	(28.26)	4.95
Basic
Continuing operations (in dollars per share)	7.35	(28.26)	5.01
Discontinued operations (in dollars per share)	(0.03)	0	(0.03)
Total (in dollars per share)	$ 7.32	$ (28.26)	$ 4.98
Stock options
Weighted-average common shares outstanding:
Effect of dilutive securities (in shares)	0.2	0.0	0.0