Commitments and Contingent Liabilities (Details)										1 Months Ended			12 Months Ended	28 Months Ended
	Apr. 22, 2020 USD ($)	Jan. 09, 2020 USD ($)	Oct. 21, 2019 USD ($) state_attorney company	Feb. 25, 2019	Apr. 03, 2018 state city	Dec. 30, 2017 investment_fund	Dec. 29, 2017 investment_fund	May 17, 2013 USD ($)	Apr. 16, 2013 defendant state relator	Dec. 31, 2019 complaint relator	Sep. 30, 2017 state_attorney	Jul. 31, 2015 USD ($)	Mar. 31, 2020 USD ($) site county case	Mar. 31, 2020 USD ($) site state_attorney state county case	Jan. 14, 2020 company	Jan. 13, 2020 case	Nov. 30, 2019 complaint	Oct. 31, 2019 complaint	Aug. 13, 2019 fax fax_number	Dec. 12, 2018 officer	Aug. 31, 2018 software_product case
Investigation into Factors Contributing to Increase in Opioid-related Hospitalizations and Deaths
Loss Contingencies [Line Items]
Number of complaints served | case													385	385
Number of states filed on behalf of											40			36
Number of plaintiffs | state_attorney														27
Number of county governments that brought case | county													2	2
Environmental Litigation
Loss Contingencies [Line Items]
Number of sites | site													5	5
Remediation costs													$ 10,000,000	$ 10,000,000
Hazardous substance sites, number | site													14
Number of sites selected for preferred remediation | site													1	1
Estimated environmental assessment and cleanup costs													$ 1,380,000,000
Estimated loss													$ 22,500,000	$ 22,500,000
Environmental Litigation | Minimum
Loss Contingencies [Line Items]
Time frame of disbursements													2020-04
Environmental Litigation | Maximum
Loss Contingencies [Line Items]
Time frame of disbursements													2050-03
In re: National Prescription Opiate Litigation
Loss Contingencies [Line Items]
Number of complaints served | case													2,800	2,800
In re: National Prescription Opiate Litigation | Pending Litigation
Loss Contingencies [Line Items]
Number of cases selected for remand to other federal courts | case																3
Number of state attorneys | state_attorney			4
Aggregate amount expected to be paid			$ 6,900,000,000
Expected payment period			18 years
In re: National Prescription Opiate Litigation | Pending Litigation | Three Largest U.S. Pharmaceutical Distributors
Loss Contingencies [Line Items]
Number of largest distributors | company			3												3
Aggregate amount expected to be paid			$ 18,000,000,000.0
Expected payment period			18 years
For Two Counties In re: National Prescription Opiate Litigation
Loss Contingencies [Line Items]
Payments for legal settlements		$ 82,000,000
In re McKesson Corporation Stockholder Derivative Litigation | Subsequent Event
Loss Contingencies [Line Items]
Amount to be received from insurance carriers	$ 175,000,000
Attorney fees awarded to the plaintiffs' counsel	$ 44,000,000
Minimum effective period of governance enhancements	4 years
United States ex rel. Manchester v. Purdue Pharma, L.P., et al
Loss Contingencies [Line Items]
Period within which party can be substituted				90 days
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]
Number of complaints | complaint										2
Number of relators alleging violations | relator										2
True Health Chiropractic Inc., et al. v. McKesson Corporation, et al
Loss Contingencies [Line Items]
Number of faxes remaining in class | fax_number																			9,490
Number of faxes received | fax																			48,769
True Health Chiropractic Inc., et al. v. McKesson Corporation, et al | Minimum
Loss Contingencies [Line Items]
Damages sought per violation								$ 500
True Health Chiropractic Inc., et al. v. McKesson Corporation, et al | Maximum
Loss Contingencies [Line Items]
Damages sought per violation								$ 1,500
Polygon European Equity Opportunity Master Fund et al. v. McKesson Europe Holdings GmbH & Co. KGaA
Loss Contingencies [Line Items]
Number of plaintiffs | investment_fund							2
Davidson Kempner International (BVI) Ltd., et al. v. McKesson Europe Holdings GmbH & Co. KGaA
Loss Contingencies [Line Items]
Number of plaintiffs | investment_fund						4
United States ex rel. Piacentile v. Amgen Inc., et al.
Loss Contingencies [Line Items]
Number of states filed on behalf of | state									21
Number of relators alleging violations | relator									2
Number of other defendants in case | defendant									5
United States ex rel. Omni Healthcare Inc. v. McKesson Corporation, et al.
Loss Contingencies [Line Items]
Number of states filed on behalf of | state					30
Number of cities filed on behalf of | city					2
Evanston Police Pension Fund v. McKesson Corporation
Loss Contingencies [Line Items]
Number of former officers | officer																				2
The Great Atlantic & Pacific Tea Company, Inc., et al
Loss Contingencies [Line Items]
Amount sought to be recovered												$ 68,000,000
Powell Prescription Center, et al. v. Surescripts, LLC, et al., and Intergrated Pharmaceutical Solutions LLC v. Surescripts, LLC
Loss Contingencies [Line Items]
Number of complaints served | 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]
Number of complaints served | complaint																	3
Consolidated Actions v SureScripts, LLC
Loss Contingencies [Line Items]
Number of complaints served | complaint										6
Civil Investigative Demands by the U.S. Attorney’s Office for the Eastern District of New York
Loss Contingencies [Line Items]
Number of complaints served | case																					2
Number of software products | software_product																					2