Document and Entity Information - USD ($) $ in Billions	12 Months Ended
	Mar. 31, 2018	Apr. 30, 2018	Sep. 30, 2017
Document And Entity Information [Abstract]
Entity Registrant Name	McKESSON CORPORATION
Entity Central Index Key	0000927653
Entity Tax Identification Number	943207296
Document Type	10-K
Current Fiscal Year End Date	--03-31
Document Period End Date	Mar. 31, 2018
Document Fiscal Period Focus	FY
Document Fiscal Year Focus	2018
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Amendment Flag	false
Entity Filer Category	Large Accelerated Filer
Entity Public Float			$ 32
Entity Common Stock, Shares Outstanding		202,050,986