Document and Entity Information	6 Months Ended
	Sep. 30, 2018 shares
Document And Entity Information [Abstract]
Entity Registrant Name	MCKESSON CORP
Entity Central Index Key	0000927653
Current Fiscal Year End Date	--03-31
Entity Filer Category	Large Accelerated Filer
Document Type	10-Q
Document Period End Date	Sep. 30, 2018
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q2
Amendment Flag	false
Entity Common Stock, Shares Outstanding (Cover)	195,376,222