Commitments and Contingent Liabilities	6 Months Ended
Sep. 30, 2017
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 also is 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 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 2017 Annual Report and our Quarterly Report on Form 10-Q for the quarter ended June 30, 2017 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 Since July 27, 2017, the Company, in many cases together with other pharmaceutical wholesale distributors and pharmaceutical manufacturers and retail pharmacy chains, has been served with 58 complaints filed in state and federal courts in Alabama, Illinois, Kentucky, Michigan, New Hampshire, New Mexico, Ohio, Oregon and Texas alleging claims related to the distribution of controlled substances to pharmacies in these states. These complaints allege violations of controlled substance laws and various other statutes in addition to common law claims, including negligence and public nuisance, and seek monetary damages and equitable relief. On October 13, 2017, IBEW Local 38 Health and Welfare Fund, a third party payor of medical costs, filed a purported class action complaint in the United States District Court for the Northern District of Ohio against various pharmaceutical manufacturers and three pharmaceutical wholesalers, including the Company, alleging that the manufacturer defendants engaged in deceptive acts involving the marketing and sales of opioids and that the distributor defendants failed to take any action to prevent or reduce the distribution of opioids. The causes of action against the distributor defendants are unjust enrichment and negligence. The suit seeks damages, including punitive and exemplary damages, all in unspecified amounts. IBEW Local 38 Health and Welfare Fund v. Purdue Pharma L.C., et al., No. 1:17-cv-02171. On July 26, 2017, Vladimir Gusinsky, as trustee for the Vladimir Gusinsky Living Trust, 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 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, all in unspecified amounts, 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 Gusinsky matter with the previously disclosed case captioned Inzlicht v. McKesson Corporation, pursuant to a stipulation between all parties to both matters. The consolidated matter is captioned 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 Court of Chancery of the State of Delaware 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, all in unspecified amounts, Steinberg v. McKesson Corporation, et.al., No. 2017-0736. 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. For example, the Company has received a request for information and documents from the states of Connecticut, Florida, Iowa, New York, North Carolina, Rhode Island, Tennessee and the Commonwealths of Massachusetts and Pennsylvania, who are leading an investigation on behalf of a multistate group of Attorneys General consisting of Alabama, Arizona, California, Colorado, Connecticut, D.C., Florida, Hawaii, Idaho, Illinois, Iowa, Kansas, Louisiana, Maine, Maryland, Massachusetts, Michigan, Minnesota, Mississippi, Missouri, Montana, Nebraska, Nevada, New Jersey, New York, North Carolina, North Dakota, Oregon, Pennsylvania, Rhode Island, South Carolina, South Dakota, Tennessee, Texas, Utah, Vermont, Virginia, Washington, and Wyoming into the factors contributing to the increasing number of opioid-related hospitalizations and deaths in the United States.

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 also is 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 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 2017 Annual Report and our Quarterly Report on Form 10-Q for the quarter ended June 30, 2017 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

Since July 27, 2017, the Company, in many cases together with other pharmaceutical wholesale distributors and pharmaceutical manufacturers and retail pharmacy chains, has been served with 58 complaints filed in state and federal courts in Alabama, Illinois, Kentucky, Michigan, New Hampshire, New Mexico, Ohio, Oregon and Texas alleging claims related to the distribution of controlled substances to pharmacies in these states. These complaints allege violations of controlled substance laws and various other statutes in addition to common law claims, including negligence and public nuisance, and seek monetary damages and equitable relief.

On October 13, 2017, IBEW Local 38 Health and Welfare Fund, a third party payor of medical costs, filed a purported class action complaint in the United States District Court for the Northern District of Ohio against various pharmaceutical manufacturers and three pharmaceutical wholesalers, including the Company, alleging that the manufacturer defendants engaged in deceptive acts involving the marketing and sales of opioids and that the distributor defendants failed to take any action to prevent or reduce the distribution of opioids. The causes of action against the distributor defendants are unjust enrichment and negligence. The suit seeks damages, including punitive and exemplary damages, all in unspecified amounts. IBEW Local 38 Health and Welfare Fund v. Purdue Pharma L.C., et al., No. 1:17-cv-02171.

On July 26, 2017, Vladimir Gusinsky, as trustee for the Vladimir Gusinsky Living Trust, 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 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, all in unspecified amounts, 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 Gusinsky matter with the previously disclosed case captioned Inzlicht v. McKesson Corporation, pursuant to a stipulation between all parties to both matters. The consolidated matter is captioned 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 Court of Chancery of the State of Delaware 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, all in unspecified amounts, Steinberg v. McKesson Corporation, et.al., No. 2017-0736.

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. For example, the Company has received a request for information and documents from the states of Connecticut, Florida, Iowa, New York, North Carolina, Rhode Island, Tennessee and the Commonwealths of Massachusetts and Pennsylvania, who are leading an investigation on behalf of a multistate group of Attorneys General consisting of Alabama, Arizona, California, Colorado, Connecticut, D.C., Florida, Hawaii, Idaho, Illinois, Iowa, Kansas, Louisiana, Maine, Maryland, Massachusetts, Michigan, Minnesota, Mississippi, Missouri, Montana, Nebraska, Nevada, New Jersey, New York, North Carolina, North Dakota, Oregon, Pennsylvania, Rhode Island, South Carolina, South Dakota, Tennessee, Texas, Utah, Vermont, Virginia, Washington, and Wyoming into the factors contributing to the increasing number of opioid-related hospitalizations and deaths in the United States.