Cover Page - USD ($) $ in Billions	12 Months Ended
	Mar. 31, 2021	Apr. 30, 2021	Sep. 30, 2020
Entity Information [Line Items]
Document Type	10-K
Document Annual Report	true
Document Period End Date	Mar. 31, 2021
Current Fiscal Year End Date	--03-31
Document Transition Report	false
Entity File Number	1-13252
Entity Registrant Name	McKESSON CORPORATION
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	94-3207296
Entity Address, Address Line One	6555 State Hwy 161
Entity Address, City or Town	Irving
Entity Address, State or Province	TX
Entity Address, Postal Zip Code	75039
City Area Code	972
Local Phone Number	446-4800
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
ICFR Auditor Attestation Flag	true
Entity Shell Company	false
Entity Public Float			$ 23.9
Entity Common Stock, Shares Outstanding		158,186,277
Documents Incorporated by Reference	DOCUMENTS INCORPORATED BY REFERENCEPortions of the registrant’s Proxy Statement for its 2021 Annual Meeting of Stockholders are incorporated by reference into Part III of this Annual Report on Form 10-K.
Entity Central Index Key	0000927653
Document Fiscal Period Focus	FY
Document Fiscal Year Focus	2021
Amendment Flag	false
Common stock, $0.01 par value
Entity Information [Line Items]
Title of 12(b) Security	Common stock, $0.01 par value
Trading Symbol	MCK
Security Exchange Name	NYSE
0.625% Notes due 2021
Entity Information [Line Items]
Title of 12(b) Security	0.625% Notes due 2021
Trading Symbol	MCK21A
Security Exchange Name	NYSE
1.500% Notes due 2025
Entity Information [Line Items]
Title of 12(b) Security	1.500% Notes due 2025
Trading Symbol	MCK25
Security Exchange Name	NYSE
1.625% Notes due 2026
Entity Information [Line Items]
Title of 12(b) Security	1.625% Notes due 2026
Trading Symbol	MCK26
Security Exchange Name	NYSE
3.125% Notes due 2029
Entity Information [Line Items]
Title of 12(b) Security	3.125% Notes due 2029
Trading Symbol	MCK29
Security Exchange Name	NYSE