Document And Entity Information (USD $) In Billions, except Share data, unless otherwise specified	12 Months Ended
	Mar. 31, 2012	Apr. 16, 2012	Sep. 30, 2011
Document And Entity Information [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Mar. 31, 2012
Document Fiscal Year Focus	2012
Document Fiscal Period Focus	FY
Entity Registrant Name	MCKESSON CORP
Entity Central Index Key	0000927653
Current Fiscal Year End Date	--03-31
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		235,397,188
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Public Float			$ 17.8