Noncontrolling Interests and Redeemable Noncontrolling Interests - Narrative (Details) shares in Millions, $ in Millions		12 Months Ended
	Sep. 19, 2018 € / shares	Mar. 31, 2024 USD ($)	Mar. 31, 2023 USD ($)	Mar. 31, 2022 USD ($) shares	Apr. 12, 2021 € / shares	Mar. 31, 2021 USD ($)	Dec. 31, 2014 € / shares
Noncontrolling Interest [Line Items]
Noncontrolling interests		$ 372	$ 367
Net income attributable to noncontrolling interests		158	162	$ 173
Put right (in euro per share) | € / shares	€ 23.50				€ 22.99
Annual increase in interest (percent)							5.00%
Put Right increase (euros per share) | € / shares	€ 0.51
Payments to purchase shares of McKesson Europe		0	0	1,031
Exercise of put right by noncontrolling shareholders of McKesson Europe AG				8
Reclassification of McKesson Europe AG redeemable noncontrolling interests				(287)
Redeemable Noncontrolling Interests
Noncontrolling Interest [Line Items]
Net income (loss) attributable to redeemable noncontrolling interest		0	0	8
Exercise of put right				983
Reclassification of McKesson Europe AG redeemable noncontrolling interests				287
Additional Paid-in Capital
Noncontrolling Interest [Line Items]
Exercise of put right by noncontrolling shareholders of McKesson Europe AG				178
Noncontrolling Interests
Noncontrolling Interest [Line Items]
Noncontrolling interests		372	367	480		$ 196
Net income attributable to noncontrolling interests		158	162	165
Exercise of put right				0
Reclassification of McKesson Europe AG redeemable noncontrolling interests				$ (287)
McKesson Europe
Noncontrolling Interest [Line Items]
Percentage of outstanding common shares				95.00%
Net income (loss) attributable to redeemable noncontrolling interest				$ 8
Put right (in euro per share) | € / shares							€ 22.99
Payments to purchase shares of McKesson Europe				$ 1,000
Shares purchased (shares) | shares				34.5
Vantage and ClarusOne Sourcing Services LLC
Noncontrolling Interest [Line Items]
Net income attributable to noncontrolling interests		$ 158	$ 162	$ 165
McKesson Europe
Noncontrolling Interest [Line Items]
Annual recurring compensation (in euro per share) | € / shares					€ 0.83		€ 0.83