Document and Entity Information	3 Months Ended
	Jun. 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	Jun. 30, 2018
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q1
Amendment Flag	false
Entity Common Stock, Shares Outstanding (Cover)	199,770,971