Commitments and Contingent Liabilities - Narrative (Details) $ in Millions				26 Months Ended
	Jan. 21, 2020	Jan. 09, 2020 USD ($)	Oct. 21, 2019 USD ($) company state_attorney	Dec. 31, 2019 USD ($) state complaint state_attorney relator case	Jan. 06, 2020 company	Nov. 30, 2019 complaint	Oct. 31, 2019 complaint	Oct. 09, 2017 case
In re: National Prescription Opioid Litigation
Loss Contingencies [Line Items]
Complaints filed against the entity				2,700
In re McKesson Corporation Stockholder Derivative Litigation
Loss Contingencies [Line Items]
Complaints filed against the entity								2
Number of new/additional suits filed				4
Amount to be paid by insurance carriers under settlement agreement | $				$ 175
Police & Fire Ret. Sys. of the City of Detroit v. McKesson Corporation, et al., Amalgamated Bank v. McKesson Corporation, et al., and Greene v. McKesson Corporation, et al.
Loss Contingencies [Line Items]
Number of new/additional suits filed				3
Powell Prescription Center, et al. v. Surescripts, LLC, et al., and Intergrated Pharmaceutical Solutions LLC v. Surescripts, LLC
Loss Contingencies [Line Items]
Complaints filed against the entity | complaint							3
Kennebunk Village Pharmacy, Inc. v. SureScripts, LLC, et al., 1:19-cv-7445; Whitman v. SureScripts, LLC et al., No. 1:19-cv-7448; BBK Global Corp. v. SureScripts, LLC et al., 1:19-cv-7640
Loss Contingencies [Line Items]
Complaints filed against the entity | complaint						3
Consolidated Actions
Loss Contingencies [Line Items]
Complaints filed against the entity | complaint				6
United States of America, ex rel. Carl Kelley and Michael McElligott, 19-cv-2233, and State of California, ex rel. Carl Kelley and Michael McElligott, CGC-19-576931
Loss Contingencies [Line Items]
Complaints filed against the entity | complaint				2
Number of relators alleging violations | relator				2
Subsequent Event | Related to Two Counties
Loss Contingencies [Line Items]
Payments under settlement agreement | $		$ 82
Subsequent Event | United States District Court for the Northern District of California, Case No. 19-cv-02869
Loss Contingencies [Line Items]
Number of days given to file amended complaint	30 days
Pending
Loss Contingencies [Line Items]
Complaints filed against the entity				360
Number of states in which court cases are pending | state				44
Number of attorney generals that have filed claims | state_attorney				20
Pending | In re: National Prescription Opioid Litigation
Loss Contingencies [Line Items]
Number of cases selected for possible remand to other federal courts				3
Number of state attorneys general involved in resolution discussions | state_attorney			4
Award payable under proposed framework | $			$ 6,900
Period over which award would be payable under proposed framework			18 years
Number of largest pharmaceutical distributors to adopt anti-diversion programs under proposed framework | company			3
Pending | Three Largest U.S. Pharmaceutical Distributors | In re: National Prescription Opioid Litigation
Loss Contingencies [Line Items]
Award payable under proposed framework | $			$ 18,000
Period over which award would be payable under proposed framework			18 years
Number of largest pharmaceutical distributors to adopt anti-diversion programs under proposed framework | company			3
Pending | Subsequent Event | Three Largest U.S. Pharmaceutical Distributors | In re: National Prescription Opioid Litigation
Loss Contingencies [Line Items]
Number of largest pharmaceutical distributors to adopt anti-diversion programs under proposed framework | company					3