Commitments and Contingent Liabilities	9 Months Ended
Dec. 31, 2019
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingent Liabilities	Commitments and Contingent Liabilities In addition to commitments and obligations incurred in the ordinary course of business, the Company is subject to a variety of claims and legal proceedings, including claims from customers and vendors, pending and potential legal actions for damages, governmental investigations and other matters. The Company and its affiliates are parties to the legal claims and proceedings described below and in Financial Note 24 to the Company’s 2019 Annual Report on Form 10-K as it was updated by Financial Note 15 to the Company’s Quarterly Report on Form 10-Q for the quarter ending June 30, 2019 and Financial Note 15 to the Company’s Quarterly Report on Form 10-Q for the quarter ended September 30, 2019, which disclosures are incorporated in this footnote by this reference. The Company is vigorously defending itself against those claims and in those proceedings. Significant developments in those matters are described below. If the Company is unsuccessful in defending, or if it determines to settle, any of these matters, it may be required to pay substantial sums, be subject to injunction and/or be forced to change how it operates its business, which could have a material adverse impact on its financial position or results of operations. Unless otherwise stated, the Company is unable to reasonably estimate the loss or a range of possible loss for the matters described below. Often, it is not reasonably possible for the Company to determine that a loss is probable for a claim, or to reasonably estimate the amount of loss or a range of loss, because of the limited information available and the potential effects of future events and decisions by third parties, such as courts and regulators, that will determine the ultimate resolution of the claim. Many of the matters described are at preliminary stages, raise novel theories of liability or seek an indeterminate amount of damages. It is not uncommon for claims to be resolved over many years. The Company reviews loss contingencies at least quarterly, to determine whether the loss probability has changed and whether it can make a reasonable estimate of the possible loss or range of loss. When the Company determines that a loss from a claim is probable and reasonably estimable, it records a liability in the amount of its estimate for the ultimate loss. The Company also provides disclosure when it is reasonably possible that a loss may be incurred or when it is reasonably possible that the amount of a loss will exceed its recorded liability. I. Litigation and Claims Involving Distribution of Controlled Substances The Company is a defendant in many cases asserting claims related to distribution of controlled substances. It is named as defendants along with other pharmaceutical wholesale distributors, pharmaceutical manufacturers and retail pharmacy chains. The plaintiffs in these actions include state attorneys general, county and municipal governments, hospitals, Indian tribes, pension funds, third-party payors and individuals. These actions have been filed in state and federal courts throughout the United States, and in Puerto Rico and Canada. They seek monetary damages and other forms of relief based on a variety of causes of action, including negligence, public nuisance, unjust enrichment, civil conspiracy, as well as alleging violations of the Racketeer Influenced and Corrupt Organizations Act (“RICO”), state and federal controlled substances laws and other statutes. Since December 5, 2017, nearly all such cases pending in federal district courts have been transferred for consolidated pre-trial proceedings to a multi-district litigation (“MDL”) in the United States District Court for the Northern District of Ohio captioned In re: National Prescription Opiate Litigation, Case No. 17-md-28-04. At present, there are approximately 2,700 cases under the jurisdiction of the MDL court. In suits filed against the Company by Cuyahoga County, Ohio, and Summit County, Ohio, the parties finalized a settlement agreement on December 26, 2019. Under the terms of the agreement, the Company did not admit liability and expressly denied wrongdoing, and paid the counties a total of $82 million on January 9, 2020. This charge was recorded within operating expenses for the nine months ended December 31, 2019. Three cases involving McKesson that were previously part of the federal MDL have been selected for possible remand to other federal courts. On January 6, 2020, with the consent of the parties involved, the MDL court suggested remand to the Judicial Panel on Multidistrict Litigation of certain claims in the case brought against the three largest distributors by Cabell County, WV, and the City of Huntington, WV. On January 14, 2020, the Judicial Panel on Multidistrict Litigation finalized its Conditional Remand Order, ordering that the cases be remanded to the U.S. District Court for the Southern District of West Virginia. On November 19, 2019, the MDL court suggested remand in the cases of the Cherokee Nation and the City and County of San Francisco. On November 20, 2019, the Judicial Panel on Multidistrict Litigation entered a Conditional Remand Order, but stayed the order pending resolution of any objections. The defendants have objected to remand of those cases, and those objections are currently pending before the Judicial Panel for Multidistrict Litigation. The Company is also named in approximately 360 similar state court cases pending in 44 states plus Puerto Rico. These include actions filed by twenty state attorneys general, and some by or on behalf of individuals, including wrongful death lawsuits and putative class action lawsuits brought on behalf of the guardians of children with neonatal abstinence syndrome due to alleged exposure to opioids in utero. Trial dates have been set in several of these state cases. Trial is currently scheduled to begin in March in a case brought by the New York attorney general and two New York county governments. The Company has been involved in discussions with the objective of achieving broad resolution of opioids-related claims brought by governmental entities. For example, on October 21, 2019, four state attorneys general announced certain terms of a proposed framework for the potential settlement of those opioid claims that they indicated they would find acceptable. The proposed framework would have expected the three largest U.S. pharmaceutical distributors to pay an aggregate amount of up to $18.0 billion over 18 years, with up to approximately $6.9 billion over 18 years expected from the Company, with any finally-determined amount being subject to adjustment based on various contingencies, including sufficient resolution with States, political subdivisions and other governmental entities nationwide. The proposed framework also would have required the three distributors, including the Company, to adopt changes to anti-diversion programs and to participate in a program involving the distribution of certain medication used to treat opioid use disorder. Because of the novelty of the claims asserted and the complexity of litigation involving numerous parties across multiple jurisdictions, the Company has determined that liability is not probable, and is not able to reasonably estimate a loss or range of loss. To be viable, a broad settlement arrangement would require participation of numerous parties and the resolution of many complex issues. The scope and terms of any settlement framework, including the financial terms, have not been determined. Because of the many uncertainties associated with any potential settlement arrangements, the Company has not reached a point where settlement is probable, and as such has not recognized any liability related to any potential settlement framework as of December 31, 2019. The Company believes that it has valid defenses to the claims pending against it and intends to vigorously defend against all such claims. An adverse judgment or negotiated resolution in any of these matters could have a material adverse impact on our financial position, cash flows or liquidity, or results of operations. On April 3, 2017, Eli Inzlicht, a purported shareholder, filed a shareholder derivative complaint in the United States District Court for the Northern District of California against certain officers and directors of the Company and the Company as a nominal defendant, alleging violations of fiduciary duties relating to the Company’s previously disclosed agreement with the Drug Enforcement Administration (“DEA”) and the Department of Justice and various United States Attorneys’ offices to settle all potential administrative and civil claims relating to investigations about the Company’s suspicious order reporting practices for controlled substances, and seeking restitution and disgorgement of all profits, benefits and other compensation obtained by the defendants from the Company and attorneys’ fees, Inzlicht v. McKesson Corporation, et.al., No. 5:17-cv-01850. On July 26, 2017, Vladimir Gusinsky, as trustee for the Vladimir Gusinsky Living Trust, a purported shareholder, filed a shareholder derivative complaint in the same court based on similar allegations, Vladimir Gusinsky, as Trustee for the Vladimir Gusinsky Living Trust v. McKesson Corporation, et.al., No. 5:17-cv-4248. On October 9, 2017, the court consolidated the two matters, In re McKesson Corporation Derivative Litigation, No. 4:17-cv-1850. On October 17, 2017, Chaile Steinberg, a purported shareholder, filed a shareholder derivative complaint in the Delaware Court of Chancery against certain officers and directors of the Company and the Company as a nominal defendant, alleging violations of fiduciary duties relating to the Company’s previously disclosed agreement with the DEA and the Department of Justice and various United States Attorneys’ offices to settle all potential administrative and civil claims relating to investigations about the Company’s suspicious order reporting practices for controlled substances, and seeking damages and disgorgement of all profits, benefits and other compensation obtained by the defendants from the Company and attorneys’ fees, Steinberg v. McKesson Corporation, et.al., No. 2017-0736. Three similar suits were thereafter filed by purported shareholders in the Court of Chancery of the State of Delaware, including Police & Fire Ret. Sys. of the City of Detroit v. McKesson Corporation, et al., No. 2017-0803, Amalgamated Bank v. McKesson Corporation, et al., No. 2017-0881, and Greene v. McKesson Corporation, et al., No. 2018-0042. The court ordered that all four actions be consolidated. The consolidated matter is captioned In re McKesson Corporation Stockholder Derivative Litigation, No. 2017-0736. Subject to court approval, the parties have reached an agreement to resolve the shareholder derivative lawsuits. Under that agreement: (i) insurance carriers would pay the Company $175 million, less any attorneys’ fees and expenses awarded by the court to plaintiffs’ counsel; and (ii) the Company would implement certain corporate governance enhancements that would remain in effect for four years after court approval of the agreement. The agreement does not include any admission of liability. II. Other Litigation and Claims On May 21, 2019, Jean E. Henry, a purported Company shareholder, filed a shareholder derivative complaint in the Superior Court of San Francisco, California against certain current and former officers and directors of the Company, and the Company as a nominal defendant, alleging violations of fiduciary duties and waste of corporate assets with respect to an alleged conspiracy to fix the prices of generic drugs, Henry v. Tyler, et al., CGC-19-576119. On May 23, 2019, the Company removed the case to the United States District Court for the Northern District of California, Case No. 19-cv-02869. On August 26, 2019, the plaintiff filed an amended complaint, removing all claims except for an alleged breach of fiduciary duty by the named current and former officers and directors of the Company. On January 21, 2020, the United States District Court for the Northern District of California granted the defendants’ motion to dismiss the complaint, and gave the shareholder 30 days to submit an amended complaint. In October 2019, the Company’s subsidiary RelayHealth Corporation (“RelayHealth”) was served with three purported class action complaints filed in the United States District Court for the Northern District of Illinois. The complaints allege that RelayHealth violated the Sherman Act by entering into an agreement with co-defendant Surescripts, LLC not to compete in the electronic prescription routing market, and by conspiring with Surescripts, LLC to monopolize that market, Powell Prescription Center, et al. v. Surescripts, LLC, et al., No. 1:19-cv-06627; Intergrated Pharmaceutical Solutions LLC v. Surescripts, LLC, et al., 1:19-cv-06778; Falconer Pharmacy, Inc. v. Surescripts LLC, et al., No. 1:19-cv-07035. In November 2019, three similar complaints were filed in the United States District Court for the Northern District of Illinois. 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. In December 2019, the six actions were consolidated in the Northern District of Illinois. The complaints seek relief including treble damages, attorney fees, and costs. In December 2019, the Company was served with two qui tam complaints filed by the same two relators alleging violations of the federal False Claims Act, the California False Claims Act, and the California Unfair Business Practices statute based on alleged predicate violations of the Controlled Substances Act and its implementing regulations, United States ex rel. Kelley, 19-cv-2233, and State of California ex rel. Kelley, CGC-19-576931. The complaints seek relief including treble damages, civil penalties, attorney fees, and costs in unspecified amounts. In December 2019, a group of independent pharmacies and a hospital filed a class action complaint in the United States District Court for the Eastern District of Pennsylvania alleging that various wholesalers, including McKesson Corporation, violated the Sherman Act by colluding with manufacturers to restrain trade in the sale of generic drugs. Reliable Pharmacy v. Actavis Holdco US, Inc., et al., No. 2:19-cv-6044. The complaint seeks relief including treble damages, disgorgement, attorney fees, and costs in unspecified amounts. III. Government Subpoenas and Investigations From time to time, the Company receives subpoenas or requests for information from various government agencies. The Company generally responds to such subpoenas and requests in a cooperative, thorough and timely manner. These responses sometimes require time and effort and can result in considerable costs being incurred by the Company. Such subpoenas and requests also can lead to the assertion of claims or the commencement of civil or criminal legal proceedings against the Company and other members of the health care industry, as well as to settlements. On November 12, 2019, the New York Department of Financial Services sent a Notice of Intent to Commence Enforcement Action to McKesson Corporation and PSS World Medical, Inc. for alleged violations of the New York Insurance Law and/or New York Financial Services Law, and seeking civil monetary penalties, in connection with manufacturing and distributing opioids in New York. In January 2020, the United States Attorney’s Office for the District of Massachusetts served a Civil Investigative Demand on the Company seeking documents related to certain discounts and rebates paid to physician practice customers.

In addition to commitments and obligations incurred in the ordinary course of business, the Company is subject to a variety of claims and legal proceedings, including claims from customers and vendors, pending and potential legal actions for damages, governmental investigations and other matters. The Company and its affiliates are parties to the legal claims and proceedings described below and in Financial Note 24 to the Company’s 2019 Annual Report on Form 10-K as it was updated by Financial Note 15 to the Company’s Quarterly Report on Form 10-Q for the quarter ending June 30, 2019 and Financial Note 15 to the Company’s Quarterly Report on Form 10-Q for the quarter ended September 30, 2019, which disclosures are incorporated in this footnote by this reference. The Company is vigorously defending itself against those claims and in those proceedings. Significant developments in those matters are described below. If the Company is unsuccessful in defending, or if it determines to settle, any of these matters, it may be required to pay substantial sums, be subject to injunction and/or be forced to change how it operates its business, which could have a material adverse impact on its financial position or results of operations.

Unless otherwise stated, the Company is unable to reasonably estimate the loss or a range of possible loss for the matters described below. Often, it is not reasonably possible for the Company to determine that a loss is probable for a claim, or to reasonably estimate the amount of loss or a range of loss, because of the limited information available and the potential effects of future events and decisions by third parties, such as courts and regulators, that will determine the ultimate resolution of the claim. Many of the matters described are at preliminary stages, raise novel theories of liability or seek an indeterminate amount of damages. It is not uncommon for claims to be resolved over many years. The Company reviews loss contingencies at least quarterly, to determine whether the loss probability has changed and whether it can make a reasonable estimate of the possible loss or range of loss. When the Company determines that a loss from a claim is probable and reasonably estimable, it records a liability in the amount of its estimate for the ultimate loss. The Company also provides disclosure when it is reasonably possible that a loss may be incurred or when it is reasonably possible that the amount of a loss will exceed its recorded liability.

The Company is a defendant in many cases asserting claims related to distribution of controlled substances. It is named as defendants along with other pharmaceutical wholesale distributors, pharmaceutical manufacturers and retail pharmacy chains. The plaintiffs in these actions include state attorneys general, county and municipal governments, hospitals, Indian tribes, pension funds, third-party payors and individuals. These actions have been filed in state and federal courts throughout the United States, and in Puerto Rico and Canada. They seek monetary damages and other forms of relief based on a variety of causes of action, including negligence, public nuisance, unjust enrichment, civil conspiracy, as well as alleging violations of the Racketeer Influenced and Corrupt Organizations Act (“RICO”), state and federal controlled substances laws and other statutes.

Since December 5, 2017, nearly all such cases pending in federal district courts have been transferred for consolidated pre-trial proceedings to a multi-district litigation (“MDL”) in the United States District Court for the Northern District of Ohio captioned In re: National Prescription Opiate Litigation, Case No. 17-md-28-04. At present, there are approximately 2,700 cases under the jurisdiction of the MDL court. In suits filed against the Company by Cuyahoga County, Ohio, and Summit County, Ohio, the parties finalized a settlement agreement on December 26, 2019. Under the terms of the agreement, the Company did not admit liability and expressly denied wrongdoing, and paid the counties a total of $82 million on January 9, 2020. This charge was recorded within operating expenses for the nine months ended December 31, 2019.

Three cases involving McKesson that were previously part of the federal MDL have been selected for possible remand to other federal courts. On January 6, 2020, with the consent of the parties involved, the MDL court suggested remand to the Judicial Panel on Multidistrict Litigation of certain claims in the case brought against the three largest distributors by Cabell County, WV, and the City of Huntington, WV. On January 14, 2020, the Judicial Panel on Multidistrict Litigation finalized its Conditional Remand Order, ordering that the cases be remanded to the U.S. District Court for the Southern District of West Virginia.

On November 19, 2019, the MDL court suggested remand in the cases of the Cherokee Nation and the City and County of San Francisco. On November 20, 2019, the Judicial Panel on Multidistrict Litigation entered a Conditional Remand Order, but stayed the order pending resolution of any objections. The defendants have objected to remand of those cases, and those objections are currently pending before the Judicial Panel for Multidistrict Litigation.

The Company is also named in approximately 360 similar state court cases pending in 44 states plus Puerto Rico. These include actions filed by twenty state attorneys general, and some by or on behalf of individuals, including wrongful death lawsuits and putative class action lawsuits brought on behalf of the guardians of children with neonatal abstinence syndrome due to alleged exposure to opioids in utero. Trial dates have been set in several of these state cases. Trial is currently scheduled to begin in March in a case brought by the New York attorney general and two New York county governments.

The Company has been involved in discussions with the objective of achieving broad resolution of opioids-related claims brought by governmental entities. For example, on October 21, 2019, four state attorneys general announced certain terms of a proposed framework for the potential settlement of those opioid claims that they indicated they would find acceptable. The proposed framework would have expected the three largest U.S. pharmaceutical distributors to pay an aggregate amount of up to $18.0 billion over 18 years, with up to approximately $6.9 billion over 18 years expected from the Company, with any finally-determined amount being subject to adjustment based on various contingencies, including sufficient resolution with States, political subdivisions and other governmental entities nationwide. The proposed framework also would have required the three distributors, including the Company, to adopt changes to anti-diversion programs and to participate in a program involving the distribution of certain medication used to treat opioid use disorder.

Because of the novelty of the claims asserted and the complexity of litigation involving numerous parties across multiple jurisdictions, the Company has determined that liability is not probable, and is not able to reasonably estimate a loss or range of loss. To be viable, a broad settlement arrangement would require participation of numerous parties and the resolution of many complex issues. The scope and terms of any settlement framework, including the financial terms, have not been determined. Because of the many uncertainties associated with any potential settlement arrangements, the Company has not reached a point where settlement is probable, and as such has not recognized any liability related to any potential settlement framework as of December 31, 2019. The Company believes that it has valid defenses to the claims pending against it and intends to vigorously defend against all such claims. An adverse judgment or negotiated resolution in any of these matters could have a material adverse impact on our financial position, cash flows or liquidity, or results of operations.

On April 3, 2017, Eli Inzlicht, a purported shareholder, filed a shareholder derivative complaint in the United States District Court for the Northern District of California against certain officers and directors of the Company and the Company as a nominal defendant, alleging violations of fiduciary duties relating to the Company’s previously disclosed agreement with the Drug Enforcement Administration (“DEA”) and the Department of Justice and various United States Attorneys’ offices to settle all potential administrative and civil claims relating to investigations about the Company’s suspicious order reporting practices for controlled substances, and seeking restitution and disgorgement of all profits, benefits and other compensation obtained by the defendants from the Company and attorneys’ fees, Inzlicht v. McKesson Corporation, et.al., No. 5:17-cv-01850. On July 26, 2017, Vladimir Gusinsky, as trustee for the Vladimir Gusinsky Living Trust, a purported shareholder, filed a shareholder derivative complaint in the same court based on similar allegations, Vladimir Gusinsky, as Trustee for the Vladimir Gusinsky Living Trust v. McKesson Corporation, et.al., No. 5:17-cv-4248. On October 9, 2017, the court consolidated the two matters, In re McKesson Corporation Derivative Litigation, No. 4:17-cv-1850.

On October 17, 2017, Chaile Steinberg, a purported shareholder, filed a shareholder derivative complaint in the Delaware Court of Chancery against certain officers and directors of the Company and the Company as a nominal defendant, alleging violations of fiduciary duties relating to the Company’s previously disclosed agreement with the DEA and the Department of Justice and various United States Attorneys’ offices to settle all potential administrative and civil claims relating to investigations about the Company’s suspicious order reporting practices for controlled substances, and seeking damages and disgorgement of all profits, benefits and other compensation obtained by the defendants from the Company and attorneys’ fees, Steinberg v. McKesson Corporation, et.al., No. 2017-0736. Three similar suits were thereafter filed by purported shareholders in the Court of Chancery of the State of Delaware, including Police & Fire Ret. Sys. of the City of Detroit v. McKesson Corporation, et al., No. 2017-0803, Amalgamated Bank v. McKesson Corporation, et al., No. 2017-0881, and Greene v. McKesson Corporation, et al., No. 2018-0042. The court ordered that all four actions be consolidated. The consolidated matter is captioned In re McKesson Corporation Stockholder Derivative Litigation, No. 2017-0736.

Subject to court approval, the parties have reached an agreement to resolve the shareholder derivative lawsuits. Under that agreement: (i) insurance carriers would pay the Company $175 million, less any attorneys’ fees and expenses awarded by the court to plaintiffs’ counsel; and (ii) the Company would implement certain corporate governance enhancements that would remain in effect for four years after court approval of the agreement. The agreement does not include any admission of liability.

On May 21, 2019, Jean E. Henry, a purported Company shareholder, filed a shareholder derivative complaint in the Superior Court of San Francisco, California against certain current and former officers and directors of the Company, and the Company as a nominal defendant, alleging violations of fiduciary duties and waste of corporate assets with respect to an alleged conspiracy to fix the prices of generic drugs, Henry v. Tyler, et al., CGC-19-576119. On May 23, 2019, the Company removed the case to the United States District Court for the Northern District of California, Case No. 19-cv-02869. On August 26, 2019, the plaintiff filed an amended complaint, removing all claims except for an alleged breach of fiduciary duty by the named current and former officers and directors of the Company. On January 21, 2020, the United States District Court for the Northern District of California granted the defendants’ motion to dismiss the complaint, and gave the shareholder 30 days to submit an amended complaint.

In October 2019, the Company’s subsidiary RelayHealth Corporation (“RelayHealth”) was served with three purported class action complaints filed in the United States District Court for the Northern District of Illinois. The complaints allege that RelayHealth violated the Sherman Act by entering into an agreement with co-defendant Surescripts, LLC not to compete in the electronic prescription routing market, and by conspiring with Surescripts, LLC to monopolize that market, Powell Prescription Center, et al. v. Surescripts, LLC, et al., No. 1:19-cv-06627; Intergrated Pharmaceutical Solutions LLC v. Surescripts, LLC, et al., 1:19-cv-06778; Falconer Pharmacy, Inc. v. Surescripts LLC, et al., No. 1:19-cv-07035. In November 2019, three similar complaints were filed in the United States District Court for the Northern District of Illinois. 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. In December 2019, the six actions were consolidated in the Northern District of Illinois. The complaints seek relief including treble damages, attorney fees, and costs.

In December 2019, the Company was served with two qui tam complaints filed by the same two relators alleging violations of the federal False Claims Act, the California False Claims Act, and the California Unfair Business Practices statute based on alleged predicate violations of the Controlled Substances Act and its implementing regulations, United States ex rel. Kelley, 19-cv-2233, and State of California ex rel. Kelley, CGC-19-576931. The complaints seek relief including treble damages, civil penalties, attorney fees, and costs in unspecified amounts.

In December 2019, a group of independent pharmacies and a hospital filed a class action complaint in the United States District Court for the Eastern District of Pennsylvania alleging that various wholesalers, including McKesson Corporation, violated the Sherman Act by colluding with manufacturers to restrain trade in the sale of generic drugs. Reliable Pharmacy v. Actavis Holdco US, Inc., et al., No. 2:19-cv-6044. The complaint seeks relief including treble damages, disgorgement, attorney fees, and costs in unspecified amounts.

From time to time, the Company receives subpoenas or requests for information from various government agencies. The Company generally responds to such subpoenas and requests in a cooperative, thorough and timely manner. These responses sometimes require time and effort and can result in considerable costs being incurred by the Company. Such subpoenas and requests also can lead to the assertion of claims or the commencement of civil or criminal legal proceedings against the Company and other members of the health care industry, as well as to settlements. On November 12, 2019, the New York Department of Financial Services sent a Notice of Intent to Commence Enforcement Action to McKesson Corporation and PSS World Medical, Inc. for alleged violations of the New York Insurance Law and/or New York Financial Services Law, and seeking civil monetary penalties, in connection with manufacturing and distributing opioids in New York. In January 2020, the United States Attorney’s Office for the District of Massachusetts served a Civil Investigative Demand on the Company seeking documents related to certain discounts and rebates paid to physician practice customers.