Earnings 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		9 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2024	Dec. 31, 2023
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Net income	$ 928	$ 630	$ 2,175	$ 2,330
Net income attributable to noncontrolling interests	(49)	(41)	(140)	(119)
Net income attributable to McKesson Corporation	$ 879	$ 589	$ 2,035	$ 2,211
Weighted-average common shares outstanding:
Basic (in shares)	126.0	132.5	128.2	134.0
Diluted (in shares)	126.6	133.3	128.8	134.9
Earnings per common share attributable to McKesson Corporation:
Diluted (in dollars per share)	$ 6.95	$ 4.42	$ 15.80	$ 16.39
Basic (in dollars per share)	$ 6.98	$ 4.45	$ 15.88	$ 16.49
Stock options
Weighted-average common shares outstanding:
Effect of dilutive securities (in shares)	0.0	0.1	0.1	0.2
Restricted stock units
Weighted-average common shares outstanding:
Effect of dilutive securities (in shares)	0.6	0.7	0.5	0.7