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		6 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Net income	$ 1,163	$ 287	$ 1,994	$ 1,247
Net income attributable to noncontrolling interests	(53)	(46)	(100)	(91)
Net income attributable to McKesson Corporation	$ 1,110	$ 241	$ 1,894	$ 1,156
Weighted-average common shares outstanding:
Basic (in shares)	124.0	128.7	124.5	129.3
Diluted (in shares)	124.4	129.3	124.9	130.0
Earnings per common share attributable to McKesson Corporation:
Diluted (in dollars per share)	$ 8.92	$ 1.87	$ 15.16	$ 8.89
Basic (in dollars per share)	$ 8.95	$ 1.88	$ 15.22	$ 8.94
Stock options
Weighted-average common shares outstanding:
Effect of dilutive securities (in shares)	0.0	0.1	0.0	0.1
Restricted stock units
Weighted-average common shares outstanding:
Effect of dilutive securities (in shares)	0.4	0.5	0.4	0.6