Commitments and Contingent Liabilities	6 Months Ended
Sep. 30, 2018
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingent Liabilities	Commitments and Contingent Liabilities In addition to commitments and obligations in the ordinary course of business, we are subject to various claims, including claims with customers and vendors, pending and potential legal actions for damages, investigations relating to governmental laws and regulations and other matters arising out of the normal conduct of our business. As described below, many of these proceedings are at preliminary stages and many seek an indeterminate amount of damages. When a loss is considered probable and reasonably estimable, we record a liability in the amount of our best estimate for the ultimate loss. However, the likelihood of a loss with respect to a particular contingency is often difficult to predict and determining a meaningful estimate of the loss or a range of loss may not be practicable based on the information available and the potential effect of future events and decisions by third parties that will determine the ultimate resolution of the contingency. Moreover, it is not uncommon for such matters to be resolved over many years, during which time relevant developments and new information must be reevaluated at least quarterly to determine both the likelihood of potential loss and whether it is possible to reasonably estimate a range of possible loss. When a loss is probable but a reasonable estimate cannot be made, disclosure of the proceeding is provided. Disclosure is also provided when it is reasonably possible that a loss will be incurred or when it is reasonably possible that the amount of a loss will exceed the recorded provision. We review all contingencies at least quarterly to determine whether the likelihood of loss has changed and to assess whether a reasonable estimate of the potential loss or range of loss can be made. As discussed above, development of a meaningful estimate of loss or a range of potential loss is complex when the outcome is directly dependent on negotiations with or decisions by third parties, such as regulatory agencies, the court system and other interested parties. Such factors bear directly on whether it is possible to reasonably estimate a range of potential loss and boundaries of high and low estimates. Significant developments in previously reported proceedings and in other litigation and claims, since the filing of our 2018 Annual Report and our Quarterly Report on Form 10-Q for the quarter ended June 30, 2018 are set out below. We are party to the legal proceedings described below. Unless otherwise stated, we are currently unable to estimate a range of reasonably possible losses for the unresolved proceedings described below. Should any one or a combination of more than one of these proceedings be successful, or should we determine to settle any or a combination of these matters, we may be required to pay substantial sums, become subject to the entry of an injunction or be forced to change the manner in which we operate our business, which could have a material adverse impact on our financial position or results of operations. Litigation, Government Subpoenas and Investigations As previously disclosed, the Company is a defendant in many cases alleging claims related to the distribution of controlled substances to pharmacies, often together with other pharmaceutical wholesale distributors and pharmaceutical manufacturers and retail pharmacy chains named as defendants. The plaintiffs in these actions include state attorneys general, county and city municipalities, hospitals, Indian tribes, pension funds, third-party payors and individuals. The Company has been served with more than 1,000 complaints filed in state and federal courts throughout the United States and in Puerto Rico. In September 2018, the Company and its subsidiary McKesson Canada Corporation were served with a purported class action by the Province of British Columbia, Canada relating to the manufacture and distribution of opioid products. Her Majesty the Queen in Right of the Province of British Columbia v. Apotex, Inc., et al.¸ Supreme Court of British Columbia, Case No. S189395. The notice of civil claim against the 15 manufacturer defendants and the 11 distributor defendants contains allegations of breach of the Competition Act, fraudulent misrepresentation and deceit, negligence, unjust enrichment and waiver of tort, and fraudulent concealment, and seeks damages for the expenses incurred by the plaintiff in paying for opioid prescriptions and other healthcare costs related to opioid addiction and abuse in British Columbia. Since December 5, 2017, nearly all the cases pending in federal district courts have been transferred to a multi-district litigation proceeding 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. On August 13, 2018, the court entered a new case management order setting forth new deadlines and moving the trial date to September 3, 2019 for the three Ohio bellwether cases, The County of Summit, Ohio v. Purdue Pharma L.P., et al., Case No. 18-OP-45090 (N.D. Ohio); The County of Cuyahoga v. Purdue Pharma L.P., et al., Case No. 17-OP45004 (N.D. Ohio); and City of Cleveland v. AmerisourceBergen Drug Corp., et al., Case No. 18-OP-4532 (N.D. Ohio.) On October 5, 2018, the magistrate judge assigned to these matters issued a report and recommendation to the district court judge on the motions to dismiss filed by the defendants in these three cases. The magistrate judge recommended granting dismissal of two claims, the common law absolute public nuisance claim and the City of Akron’s public nuisance claim. The report otherwise recommended denying all the defendants’ motions to dismiss. The defendants’ objections to the magistrate judge’s report to the district court are due on November 2, 2018. As previously disclosed, the two shareholder derivative complaints filed in the United States District Court for the Northern District of California were consolidated under the caption In re McKesson Corporation Derivative Litigation, No. 4:17-cv-1850. On September 17, 2018, a Special Litigation Committee established by the Board of Directors of the Company moved to stay the litigation while the Special Litigation Committee conducts an independent investigation concerning the plaintiffs’ allegations. As previously disclosed, on June 15, 2018, an amended complaint was filed in the United States District Court for the Southern District of Illinois alleging that McKesson Medical-Surgical Inc., among others, violated the Sherman Act by restraining trade in the sale of safety and conventional syringes and safety IV catheters. Marion Diagnostic Center, LLC v. Becton, Dickinson, and Co., No. 18:1059. On July 20, 2018, the defendants filed a motion to dismiss and a hearing was held on October 17, 2018. On September 25, 2018, the same plaintiff filed a complaint in the Eastern District of Pennsylvania alleging that the Company and McKesson Medical-Surgical Inc., among others, violated the Sherman Act by restraining trade in the sale of generic drugs. Marion Diagnostic Center, LLC v. McKesson Corporation, et al., No. 2:18-cv-4137. As previously disclosed, on April 16, 2013, the Company’s wholly-owned subsidiary, U.S. Oncology, Inc. (“USON”) was served with a third amended qui tam complaint filed in the United States District Court for the Eastern District of New York alleging that USON solicited and received illegal “kickbacks” from Amgen in violation of the Anti-Kickback Statute, the False Claims Act, and various state false claims statutes, United States ex rel. Piacentile v. Amgen, Inc., et al., CV 04-3983. Previously, the United States declined to intervene in the case as to all allegations and defendants except for Amgen. On April 4, 2014, USON filed a motion to dismiss the claims against it. On September 17, 2018, the court granted USON’s motion to dismiss, and subsequently gave the relator until November 16, 2018 to amend the complaint. As previously disclosed, on June 17, 2014, the Company’s subsidiary, U.S. Oncology Specialty, LP (“USOS”) was served with a fifth amended qui tam complaint filed in the United States District Court for the Eastern District of New York alleging that USOS solicited and received illegal “kickback” from Amgen in violation of the Anti-Kickback Statute, the False Claims Act, and various state false claims statutes, United States ex rel. Hanks v. Amgen, Inc., et al., CV 08-03096. Previously, the United States declined to intervene in the case as to all allegations and defendants except for Amgen. On August 1, 2014, USOS filed a motion to dismiss the claims against it. On September 17, 2018, the court granted USOS’s motion to dismiss and gave the relator leave to file another action after the Piacentile action is no longer pending. As previously disclosed, on March 5, 2018, the Company’s subsidiary, RxC Acquisition Company (doing business as RxCrossroads) was served with a qui tam complaint filed in the United States District Court for the Southern District of Illinois alleging that UCB, Inc. provided illegal “kickbacks’ to providers, including services provided through Rxc Acquisition Company, in violation of the Anti-kickback statute, the False Claims Act, and various state false claims statutes. United States ex rel. CIMZHNCA, LLC v. UCB, Inc., et al., No. 17-cv-00765. On April 26, 2018, the defendants filed a motion to transfer the suit to the United States District Court for the District of New Jersey. As previously disclosed, on April 3, 2018, a second amended qui tam complaint was filed in the United States District Court for the Eastern District of New York by a relator, purportedly on behalf of the United States, 30 states, the District of Columbia, and two cities against the Company, McKesson Specialty Care Distribution, McKesson Specialty Distribution LLC, McKesson Specialty Care Distribution Joint Venture, L.P., Oncology Therapeutics Network Corporation, Oncology Therapeutics Network Joint Venture, L.P., U.S. Oncology, Inc. and U.S. Oncology Specialty, L.P., alleging that from 2001 through 2010 the defendants repackaged and sold single-dose syringes of oncology medications in a manner that violated the federal False Claims Act and various state and local false claims statutes. United States ex rel. Omni Healthcare Inc. v. McKesson Corporation, et al., 12-cv-06440. The United States and the states have declined to intervene in the case. On October 15, 2018, the defendants filed a motion to dismiss the complaint. As previously disclosed, on December 29, 2017, two investment funds holding shares in Celesio AG filed a complaint against the Company’s wholly-owned subsidiary McKesson Europe Holdings in a German court in Stuttgart, Germany, Polygon European Equity Opportunity Master Fund et al. v. McKesson Europe Holdings GmbH & Co. KGaA, No. 18 O 455/17 (the “Polygon” matter). The complaint alleges that the public tender offer document published by McKesson Europe in its acquisition of Celesio AG incorrectly states that McKesson Europe’s acquisition of convertible bonds would not be treated as a relevant acquisition of shares for the purposes of triggering minimum pricing considerations under the German Takeover Offer Ordinance. On December 30, 2017, four additional funds filed a substantially identical claim, Davidson Kempner International (BVI) Ltd., et al. v. McKesson Europe Holdings GmbH & Co. KGaA, No. 16 O 475/17 (the “Davidson” matter.) On May 11, 2018, the court in the Polygon matter dismissed the claims against McKesson Europe. Plaintiffs appealed and McKesson Europe filed responsive appellate briefing on September 20, 2018 and a hearing is scheduled for November 21, 2018. McKesson Europe filed its statement of defense in the Davidson matter on April 21, 2018 and the hearing is scheduled to take place on January 31, 2019. 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 matter. 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 healthcare industry. As previously disclosed, in May 2017, the Company was served with a Civil Investigative Demand by the U.S. Attorney’s Office for the Eastern District of New York related to the certification it obtained for a software product under the U.S. Department of Health and Human Services’ Electronic Health Record Incentive Program. In August 2018, the Company received another Civil Investigative Demand from the same U.S. Attorney’s Office related to the certification it obtained for a different software product under the same government incentive program. New York Opioid Statute Legislative, regulatory or industry measures to address the misuse of prescription opioid medications could affect the Company’s business in ways that we may not be able to predict. For example, in April 2018, the State of New York adopted the Opioid Stewardship Act (the “OSA”) which required the creation of an aggregate $100 million annual surcharge on all manufacturers and distributors licensed to sell or distribute opioids in New York. The initial surcharge payment is due on January 1, 2019 for opioids sold or distributed during calendar year 2017. It is uncertain at this point in time what proportion of this estimated liability will be ultimately borne by the Company because the Company’s share of the surcharge depends heavily on what other licensees report. The Company has estimated and reflected a liability for the OSA surcharge in its accompanying condensed consolidated financial statements. However, it is possible that the ultimate costs may exceed or be less than the reserve. Moreover, on July 6, 2018, the Healthcare Distribution Alliance filed a lawsuit challenging the constitutionality of the law and seeking an injunction against its enforcement. We are not able to predict whether this lawsuit will be successful. In addition, other states are considering legislation that could require us to pay taxes or assessments on the distribution of opioid medications in those states. These proposed bills vary in the amounts and the means of calculation. Liabilities for taxes or assessments under any such laws will likely have an adverse impact on our results of operations, unless we are able to mitigate them through operational changes or commercial arrangements where permitted.

Commitments and Contingent Liabilities

In addition to commitments and obligations in the ordinary course of business, we are subject to various claims, including claims with customers and vendors, pending and potential legal actions for damages, investigations relating to governmental laws and regulations and other matters arising out of the normal conduct of our business. As described below, many of these proceedings are at preliminary stages and many seek an indeterminate amount of damages.

When a loss is considered probable and reasonably estimable, we record a liability in the amount of our best estimate for the ultimate loss. However, the likelihood of a loss with respect to a particular contingency is often difficult to predict and determining a meaningful estimate of the loss or a range of loss may not be practicable based on the information available and the potential effect of future events and decisions by third parties that will determine the ultimate resolution of the contingency. Moreover, it is not uncommon for such matters to be resolved over many years, during which time relevant developments and new information must be reevaluated at least quarterly to determine both the likelihood of potential loss and whether it is possible to reasonably estimate a range of possible loss. When a loss is probable but a reasonable estimate cannot be made, disclosure of the proceeding is provided.

Disclosure is also provided when it is reasonably possible that a loss will be incurred or when it is reasonably possible that the amount of a loss will exceed the recorded provision. We review all contingencies at least quarterly to determine whether the likelihood of loss has changed and to assess whether a reasonable estimate of the potential loss or range of loss can be made. As discussed above, development of a meaningful estimate of loss or a range of potential loss is complex when the outcome is directly dependent on negotiations with or decisions by third parties, such as regulatory agencies, the court system and other interested parties. Such factors bear directly on whether it is possible to reasonably estimate a range of potential loss and boundaries of high and low estimates.

Significant developments in previously reported proceedings and in other litigation and claims, since the filing of our 2018 Annual Report and our Quarterly Report on Form 10-Q for the quarter ended June 30, 2018 are set out below. We are party to the legal proceedings described below. Unless otherwise stated, we are currently unable to estimate a range of reasonably possible losses for the unresolved proceedings described below. Should any one or a combination of more than one of these proceedings be successful, or should we determine to settle any or a combination of these matters, we may be required to pay substantial sums, become subject to the entry of an injunction or be forced to change the manner in which we operate our business, which could have a material adverse impact on our financial position or results of operations.

Litigation, Government Subpoenas and Investigations

As previously disclosed, the Company is a defendant in many cases alleging claims related to the distribution of controlled substances to pharmacies, often together with other pharmaceutical wholesale distributors and pharmaceutical manufacturers and retail pharmacy chains named as defendants. The plaintiffs in these actions include state attorneys general, county and city municipalities, hospitals, Indian tribes, pension funds, third-party payors and individuals. The Company has been served with more than 1,000 complaints filed in state and federal courts throughout the United States and in Puerto Rico. In September 2018, the Company and its subsidiary McKesson Canada Corporation were served with a purported class action by the Province of British Columbia, Canada relating to the manufacture and distribution of opioid products. Her Majesty the Queen in Right of the Province of British Columbia v. Apotex, Inc., et al.¸ Supreme Court of British Columbia, Case No. S189395. The notice of civil claim against the 15 manufacturer defendants and the 11 distributor defendants contains allegations of breach of the Competition Act, fraudulent misrepresentation and deceit, negligence, unjust enrichment and waiver of tort, and fraudulent concealment, and seeks damages for the expenses incurred by the plaintiff in paying for opioid prescriptions and other healthcare costs related to opioid addiction and abuse in British Columbia. Since December 5, 2017, nearly all the cases pending in federal district courts have been transferred to a multi-district litigation proceeding 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. On August 13, 2018, the court entered a new case management order setting forth new deadlines and moving the trial date to September 3, 2019 for the three Ohio bellwether cases, The County of Summit, Ohio v. Purdue Pharma L.P., et al., Case No. 18-OP-45090 (N.D. Ohio); The County of Cuyahoga v. Purdue Pharma L.P., et al., Case No. 17-OP45004 (N.D. Ohio); and City of Cleveland v. AmerisourceBergen Drug Corp., et al., Case No. 18-OP-4532 (N.D. Ohio.) On October 5, 2018, the magistrate judge assigned to these matters issued a report and recommendation to the district court judge on the motions to dismiss filed by the defendants in these three cases. The magistrate judge recommended granting dismissal of two claims, the common law absolute public nuisance claim and the City of Akron’s public nuisance claim. The report otherwise recommended denying all the defendants’ motions to dismiss. The defendants’ objections to the magistrate judge’s report to the district court are due on November 2, 2018.

As previously disclosed, the two shareholder derivative complaints filed in the United States District Court for the Northern District of California were consolidated under the caption In re McKesson Corporation Derivative Litigation, No. 4:17-cv-1850. On September 17, 2018, a Special Litigation Committee established by the Board of Directors of the Company moved to stay the litigation while the Special Litigation Committee conducts an independent investigation concerning the plaintiffs’ allegations.

As previously disclosed, on June 15, 2018, an amended complaint was filed in the United States District Court for the Southern District of Illinois alleging that McKesson Medical-Surgical Inc., among others, violated the Sherman Act by restraining trade in the sale of safety and conventional syringes and safety IV catheters. Marion Diagnostic Center, LLC v. Becton, Dickinson, and Co., No. 18:1059. On July 20, 2018, the defendants filed a motion to dismiss and a hearing was held on October 17, 2018. On September 25, 2018, the same plaintiff filed a complaint in the Eastern District of Pennsylvania alleging that the Company and McKesson Medical-Surgical Inc., among others, violated the Sherman Act by restraining trade in the sale of generic drugs. Marion Diagnostic Center, LLC v. McKesson Corporation, et al., No. 2:18-cv-4137.

As previously disclosed, on April 16, 2013, the Company’s wholly-owned subsidiary, U.S. Oncology, Inc. (“USON”) was served with a third amended qui tam complaint filed in the United States District Court for the Eastern District of New York alleging that USON solicited and received illegal “kickbacks” from Amgen in violation of the Anti-Kickback Statute, the False Claims Act, and various state false claims statutes, United States ex rel. Piacentile v. Amgen, Inc., et al., CV 04-3983. Previously, the United States declined to intervene in the case as to all allegations and defendants except for Amgen. On April 4, 2014, USON filed a motion to dismiss the claims against it. On September 17, 2018, the court granted USON’s motion to dismiss, and subsequently gave the relator until November 16, 2018 to amend the complaint.

As previously disclosed, on June 17, 2014, the Company’s subsidiary, U.S. Oncology Specialty, LP (“USOS”) was served with a fifth amended qui tam complaint filed in the United States District Court for the Eastern District of New York alleging that USOS solicited and received illegal “kickback” from Amgen in violation of the Anti-Kickback Statute, the False Claims Act, and various state false claims statutes, United States ex rel. Hanks v. Amgen, Inc., et al., CV 08-03096. Previously, the United States declined to intervene in the case as to all allegations and defendants except for Amgen. On August 1, 2014, USOS filed a motion to dismiss the claims against it. On September 17, 2018, the court granted USOS’s motion to dismiss and gave the relator leave to file another action after the Piacentile action is no longer pending.

As previously disclosed, on March 5, 2018, the Company’s subsidiary, RxC Acquisition Company (doing business as RxCrossroads) was served with a qui tam complaint filed in the United States District Court for the Southern District of Illinois alleging that UCB, Inc. provided illegal “kickbacks’ to providers, including services provided through Rxc Acquisition Company, in violation of the Anti-kickback statute, the False Claims Act, and various state false claims statutes. United States ex rel. CIMZHNCA, LLC v. UCB, Inc., et al., No. 17-cv-00765. On April 26, 2018, the defendants filed a motion to transfer the suit to the United States District Court for the District of New Jersey.

As previously disclosed, on April 3, 2018, a second amended qui tam complaint was filed in the United States District Court for the Eastern District of New York by a relator, purportedly on behalf of the United States, 30 states, the District of Columbia, and two cities against the Company, McKesson Specialty Care Distribution, McKesson Specialty Distribution LLC, McKesson Specialty Care Distribution Joint Venture, L.P., Oncology Therapeutics Network Corporation, Oncology Therapeutics Network Joint Venture, L.P., U.S. Oncology, Inc. and U.S. Oncology Specialty, L.P., alleging that from 2001 through 2010 the defendants repackaged and sold single-dose syringes of oncology medications in a manner that violated the federal False Claims Act and various state and local false claims statutes. United States ex rel. Omni Healthcare Inc. v. McKesson Corporation, et al., 12-cv-06440. The United States and the states have declined to intervene in the case. On October 15, 2018, the defendants filed a motion to dismiss the complaint.

As previously disclosed, on December 29, 2017, two investment funds holding shares in Celesio AG filed a complaint against the Company’s wholly-owned subsidiary McKesson Europe Holdings in a German court in Stuttgart, Germany, Polygon European Equity Opportunity Master Fund et al. v. McKesson Europe Holdings GmbH & Co. KGaA, No. 18 O 455/17 (the “Polygon” matter). The complaint alleges that the public tender offer document published by McKesson Europe in its acquisition of Celesio AG incorrectly states that McKesson Europe’s acquisition of convertible bonds would not be treated as a relevant acquisition of shares for the purposes of triggering minimum pricing considerations under the German Takeover Offer Ordinance. On December 30, 2017, four additional funds filed a substantially identical claim, Davidson Kempner International (BVI) Ltd., et al. v. McKesson Europe Holdings GmbH & Co. KGaA, No. 16 O 475/17 (the “Davidson” matter.) On May 11, 2018, the court in the Polygon matter dismissed the claims against McKesson Europe. Plaintiffs appealed and McKesson Europe filed responsive appellate briefing on September 20, 2018 and a hearing is scheduled for November 21, 2018. McKesson Europe filed its statement of defense in the Davidson matter on April 21, 2018 and the hearing is scheduled to take place on January 31, 2019.

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 matter. 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 healthcare industry. As previously disclosed, in May 2017, the Company was served with a Civil Investigative Demand by the U.S. Attorney’s Office for the Eastern District of New York related to the certification it obtained for a software product under the U.S. Department of Health and Human Services’ Electronic Health Record Incentive Program. In August 2018, the Company received another Civil Investigative Demand from the same U.S. Attorney’s Office related to the certification it obtained for a different software product under the same government incentive program.

New York Opioid Statute

Legislative, regulatory or industry measures to address the misuse of prescription opioid medications could affect the Company’s business in ways that we may not be able to predict. For example, in April 2018, the State of New York adopted the Opioid Stewardship Act (the “OSA”) which required the creation of an aggregate $100 million annual surcharge on all manufacturers and distributors licensed to sell or distribute opioids in New York. The initial surcharge payment is due on January 1, 2019 for opioids sold or distributed during calendar year 2017. It is uncertain at this point in time what proportion of this estimated liability will be ultimately borne by the Company because the Company’s share of the surcharge depends heavily on what other licensees report. The Company has estimated and reflected a liability for the OSA surcharge in its accompanying condensed consolidated financial statements. However, it is possible that the ultimate costs may exceed or be less than the reserve. Moreover, on July 6, 2018, the Healthcare Distribution Alliance filed a lawsuit challenging the constitutionality of the law and seeking an injunction against its enforcement. We are not able to predict whether this lawsuit will be successful. In addition, other states are considering legislation that could require us to pay taxes or assessments on the distribution of opioid medications in those states. These proposed bills vary in the amounts and the means of calculation. Liabilities for taxes or assessments under any such laws will likely have an adverse impact on our results of operations, unless we are able to mitigate them through operational changes or commercial arrangements where permitted.