Redeemable Noncontrolling Interests and Noncontrolling Interests - Narrative (Details) shares in Millions		12 Months Ended
	Sep. 19, 2018 € / shares	Mar. 31, 2022 USD ($) shares	Mar. 31, 2021 USD ($) shares	Mar. 31, 2020 USD ($)	Apr. 12, 2021 € / shares	Mar. 31, 2019 USD ($)	Dec. 31, 2014 € / shares
Noncontrolling Interest [Line Items]
Put right (in euro per share) | € / shares	€ 23.50				€ 22.99
Annual increase in interest (percent)							5.00%
Payments to purchase shares of McKesson Europe		$ 1,031,000,000	$ 49,000,000	$ 3,000,000
Exercise of put right by noncontrolling shareholders of McKesson Europe AG		8,000,000	3,000,000
Carrying amount of redeemable noncontrolling interest		0	1,271,000,000
Put Right increase (euros per share) | € / shares	€ 0.51
Noncontrolling interests		480,000,000	196,000,000
Net income attributable to noncontrolling interests		173,000,000	199,000,000	220,000,000
Redeemable Noncontrolling Interests
Noncontrolling Interest [Line Items]
Net Income (Loss) Attributable to Redeemable Noncontrolling Interest		8,000,000	43,000,000	42,000,000
Exercises of Put Right		(983,000,000)	(49,000,000)
Carrying amount of redeemable noncontrolling interest		0	1,271,000,000	1,402,000,000		$ 1,393,000,000
Additional Paid-in Capital
Noncontrolling Interest [Line Items]
Exercise of put right by noncontrolling shareholders of McKesson Europe AG		178,000,000	3,000,000
Noncontrolling Interests
Noncontrolling Interest [Line Items]
Exercises of Put Right		0	0
Noncontrolling interests		480,000,000	196,000,000	217,000,000		$ 193,000,000
Net income attributable to noncontrolling interests		165,000,000	156,000,000	178,000,000
McKesson Europe
Noncontrolling Interest [Line Items]
Net Income (Loss) Attributable to Redeemable Noncontrolling Interest		8,000,000	43,000,000	42,000,000
Put right (in euro per share) | € / shares							€ 22.99
Payments to purchase shares of McKesson Europe		$ 1,000,000,000	$ 49,000,000
Shares purchased (shares) | shares		34.5	1.8
Maximum redemption value			$ 1,200,000,000
Percentage of outstanding common shares		95.00%	78.00%
Vantage and ClarusOne Sourcing Services LLC
Noncontrolling Interest [Line Items]
Net income attributable to noncontrolling interests		$ 165,000,000	$ 156,000,000	$ 178,000,000
McKesson Europe
Noncontrolling Interest [Line Items]
Annual recurring compensation (in euro per share) | € / shares					€ 0.83		€ 0.83