Significant Accounting Policies	9 Months Ended
Dec. 31, 2015
Accounting Policies [Abstract]
Significant Accounting Policies	Significant Accounting Policies Basis of Presentation: The condensed consolidated financial statements of McKesson Corporation (“McKesson,” the “Company,” or “we” and other similar pronouns) include the financial statements of all wholly-owned subsidiaries and majority‑owned or controlled companies. We also evaluate our ownership, contractual and other interests in entities to determine if they are variable interest entities (“VIEs”), if we have a variable interest in those entities and the nature and extent of those variable interests. These evaluations are highly complex and involve judgment and the use of estimates and assumptions based on available historical information and management’s judgment, among other factors. Based on our evaluations, if we determine we are the primary beneficiary of such VIEs, we consolidate such entities into our financial statements. Investments in business entities in which we do not have control, but have the ability to exercise significant influence over operating and financial policies, are accounted for using the equity method and our proportionate share of income or loss is recorded in Other Income, Net. Intercompany transactions and balances have been eliminated. The condensed consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America (“GAAP”) for interim financial reporting and the rules and regulations of the U.S. Securities and Exchange Commission (“SEC”) and, therefore, do not include all information and disclosures normally included in the annual consolidated financial statements. To prepare the financial statements in conformity with GAAP, management must make estimates and assumptions that affect the reported amounts of assets and liabilities as of the date of these financial statements and income and expenses during the reporting period. Actual amounts may differ from these estimated amounts. In our opinion, the accompanying unaudited condensed consolidated financial statements include all normal recurring adjustments necessary for a fair presentation of our financial position, results of operations and cash flows for the interim periods presented. The results of operations for the quarter and nine months ended December 31, 2015 are not necessarily indicative of the results that may be expected for the entire year. These interim financial statements should be read in conjunction with the annual audited financial statements, accounting policies and financial notes included in our Annual Report on Form 10-K for the fiscal year ended March 31, 2015 previously filed with the SEC on May 12, 2015 (“2015 Annual Report”). Certain prior period amounts, which relate to our discontinued operations, have been reclassified to conform to the current period presentation. The Company’s fiscal year begins on April 1 and ends on March 31. Unless otherwise noted, all references to a particular year shall mean the Company’s fiscal year. Recently Adopted Accounting Pronouncements Discontinued Operations: In the first quarter of 2016, we adopted amended guidance for reporting of discontinued operations and disclosures of disposals of components. The amended guidance revises the criteria for disposals to qualify as discontinued operations and permits significant continuing involvement and continuing cash flows with the discontinued operation. In addition, the amended guidance requires additional disclosures for discontinued operations and new disclosures for individually material disposal transactions that do not meet the definition of a discontinued operation. Refer to Financial Notes 4 and 5, “Divestiture of Businesses” and “Discontinued Operations,” for more information regarding the impact of this amended guidance on our condensed consolidated financial statements. Recently Issued Accounting Pronouncements Not Yet Adopted Financial Instruments: In January 2016, amended guidance was issued that requires equity investments to be measured at fair value with changes in fair value recognized in net income and enhanced disclosures about those investments. This guidance also simplifies the impairment assessments of equity investments without readily determinable fair value. The investments that are accounted for under the equity method of accounting or result in consolidation of the investee are excluded from the scope of this amended guidance. The amended guidance will become effective for us commencing in the first quarter of 2019 and will be adopted through a cumulative-effect adjustment. Early adoption is not permitted except for certain provisions. We are currently evaluating the impact of this amended guidance on our consolidated financial statements. Deferred Income Taxes: In November 2015, amended guidance was issued for the balance sheet classification of deferred income taxes. The amended guidance requires the classification of all deferred tax assets and liabilities as noncurrent on the balance sheet instead of separating deferred taxes into current and noncurrent amounts. Deferred tax assets and liabilities will continue to be offset and presented as a single amount under the amended guidance. The amended guidance will become effective for us commencing in the first quarter of 2018 and will only result in a change in presentation of these deferred taxes on our consolidated balance sheets. The amended guidance can be adopted either on a prospective or retrospective basis. Early adoption is permitted. We are currently evaluating the impact of this amended guidance on our condensed consolidated financial statements. Business Combinations: In September 2015, amended guidance was issued for an acquirer’s accounting for measurement-period adjustments. The amended guidance eliminates the requirement that an acquirer in a business combination account for measurement-period adjustments retrospectively and instead requires that measurement-period adjustments be recognized during the period in which it determines the adjustment. In addition, the amended guidance requires that the acquirer record, in the same period’s financial statements, the effect on earnings of changes in depreciation, amortization, or other income effects, if any, as a result of the change to the provisional amounts, calculated as if the accounting had been completed at the acquisition date. The amended guidance is effective for us prospectively commencing in the first quarter of 2017. Early adoption is permitted. Inventory: In July 2015, amended guidance was issued for the subsequent measurement of inventory. The amended guidance requires entities to measure inventory at the lower of cost or net realizable value. Net realizable value is the estimated selling prices in the ordinary course of business, less reasonably predictable costs of completion, disposal, and transportation. The requirement would replace the current lower of cost or market evaluation. Accounting guidance is unchanged for inventory measured using last-in, first-out (“LIFO”) or the retail method. The amended guidance will become effective for us commencing in the first quarter of 2018. Early adoption is permitted. We are currently evaluating the impact of this amended guidance on our condensed consolidated financial statements. Fair Value Measurement: In May 2015, amended guidance was issued that limits disclosures and removes the requirement to categorize investments within the fair value hierarchy if the fair value of the investment is measured using the net asset value per share practical expedient. The amended guidance will become effective for us retrospectively commencing in the first quarter of 2017. Early adoption is permitted. This amended guidance is primarily expected to affect our annual disclosures related to our pension benefits. We are currently evaluating the impact of this amended guidance on our condensed consolidated financial statements. Fees Paid in a Cloud Computing Arrangement: In April 2015, amended guidance was issued for a customer’s accounting for fees paid in a cloud computing arrangement. The amended guidance requires customers to determine whether or not an arrangement contains a software license element. If the arrangement contains a software element, the related fees paid should be accounted for as an acquisition of a software license. If the arrangement does not contain a software license, it is accounted for as a service contract. The amended guidance will become effective for us commencing in the first quarter of 2017. Early adoption is permitted. We are currently evaluating the impact of this amended guidance on our condensed consolidated financial statements. Debt Issuance Costs: In April 2015, amended guidance was issued for the balance sheet presentation of debt issuance costs. The amended guidance requires debt issuance costs related to a recognized debt liability to be reported on the balance sheet as a direct deduction from the carrying amount of that debt liability. The recognition and measurement guidance for debt issuance costs is not affected by the amended guidance. In August 2015, a clarification was added to this amended guidance that debt issuance costs related to line-of-credit arrangements can continue to be deferred and presented as an asset on the balance sheet. The amended guidance will become effective for us commencing in the first quarter of 2017. Early adoption is permitted. The amended guidance will affect financial statement presentation only and therefore we do not expect the adoption of this guidance to have a material effect on our condensed consolidated financial statements. Consolidation: In February 2015, amended guidance was issued for consolidating legal entities in which a reporting entity holds a variable interest. The amended guidance modifies the evaluation of whether limited partnerships and similar legal entities are VIEs and changes the consolidation analysis of reporting entities that are involved with VIEs that have fee arrangements and related party relationships. The amended guidance will become effective for us commencing in the first quarter of 2017. Early adoption is permitted. We are currently evaluating the impact of this amended guidance on our condensed consolidated financial statements. Revenue Recognition: In May 2014, amended guidance was issued for recognizing revenue from contracts with customers. The amended guidance eliminates industry specific guidance and applies to all companies. Revenues will be recognized when an entity satisfies a performance obligation by transferring control of a promised good or service to a customer in an amount that reflects the consideration to which the entity expects to be entitled for that good or service. Revenue from a contract that contains multiple performance obligations is allocated to each performance obligation generally on a relative standalone selling price basis. The amended guidance also requires additional quantitative and qualitative disclosures. In August 2015, additional guidance was issued to defer the effective date of the amended revenue recognition guidance by one year. As a result, the amended guidance is effective for us commencing in the first quarter of 2019. The amended guidance allows for either full retrospective adoption or modified retrospective adoption. Early adoption is permitted but not prior to our first quarter of 2018. We are currently evaluating the impact of this amended guidance on our condensed consolidated financial statements.

Significant Accounting Policies

Basis of Presentation: The condensed consolidated financial statements of McKesson Corporation (“McKesson,” the “Company,” or “we” and other similar pronouns) include the financial statements of all wholly-owned subsidiaries and majority‑owned or controlled companies. We also evaluate our ownership, contractual and other interests in entities to determine if they are variable interest entities (“VIEs”), if we have a variable interest in those entities and the nature and extent of those variable interests. These evaluations are highly complex and involve judgment and the use of estimates and assumptions based on available historical information and management’s judgment, among other factors. Based on our evaluations, if we determine we are the primary beneficiary of such VIEs, we consolidate such entities into our financial statements. Investments in business entities in which we do not have control, but have the ability to exercise significant influence over operating and financial policies, are accounted for using the equity method and our proportionate share of income or loss is recorded in Other Income, Net. Intercompany transactions and balances have been eliminated. The condensed consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America (“GAAP”) for interim financial reporting and the rules and regulations of the U.S. Securities and Exchange Commission (“SEC”) and, therefore, do not include all information and disclosures normally included in the annual consolidated financial statements.

To prepare the financial statements in conformity with GAAP, management must make estimates and assumptions that affect the reported amounts of assets and liabilities as of the date of these financial statements and income and expenses during the reporting period. Actual amounts may differ from these estimated amounts. In our opinion, the accompanying unaudited condensed consolidated financial statements include all normal recurring adjustments necessary for a fair presentation of our financial position, results of operations and cash flows for the interim periods presented.

The results of operations for the quarter and nine months ended December 31, 2015 are not necessarily indicative of the results that may be expected for the entire year. These interim financial statements should be read in conjunction with the annual audited financial statements, accounting policies and financial notes included in our Annual Report on Form 10-K for the fiscal year ended March 31, 2015 previously filed with the SEC on May 12, 2015 (“2015 Annual Report”).

Certain prior period amounts, which relate to our discontinued operations, have been reclassified to conform to the current period presentation.

The Company’s fiscal year begins on April 1 and ends on March 31. Unless otherwise noted, all references to a particular year shall mean the Company’s fiscal year.

Recently Adopted Accounting Pronouncements

Discontinued Operations: In the first quarter of 2016, we adopted amended guidance for reporting of discontinued operations and disclosures of disposals of components. The amended guidance revises the criteria for disposals to qualify as discontinued operations and permits significant continuing involvement and continuing cash flows with the discontinued operation. In addition, the amended guidance requires additional disclosures for discontinued operations and new disclosures for individually material disposal transactions that do not meet the definition of a discontinued operation. Refer to Financial Notes 4 and 5, “Divestiture of Businesses” and “Discontinued Operations,” for more information regarding the impact of this amended guidance on our condensed consolidated financial statements.

Recently Issued Accounting Pronouncements Not Yet Adopted

Financial Instruments: In January 2016, amended guidance was issued that requires equity investments to be measured at fair value with changes in fair value recognized in net income and enhanced disclosures about those investments. This guidance also simplifies the impairment assessments of equity investments without readily determinable fair value. The investments that are accounted for under the equity method of accounting or result in consolidation of the investee are excluded from the scope of this amended guidance. The amended guidance will become effective for us commencing in the first quarter of 2019 and will be adopted through a cumulative-effect adjustment. Early adoption is not permitted except for certain provisions. We are currently evaluating the impact of this amended guidance on our consolidated financial statements.

Deferred Income Taxes: In November 2015, amended guidance was issued for the balance sheet classification of deferred income taxes. The amended guidance requires the classification of all deferred tax assets and liabilities as noncurrent on the balance sheet instead of separating deferred taxes into current and noncurrent amounts. Deferred tax assets and liabilities will continue to be offset and presented as a single amount under the amended guidance. The amended guidance will become effective for us commencing in the first quarter of 2018 and will only result in a change in presentation of these deferred taxes on our consolidated balance sheets. The amended guidance can be adopted either on a prospective or retrospective basis. Early adoption is permitted. We are currently evaluating the impact of this amended guidance on our condensed consolidated financial statements.

Business Combinations: In September 2015, amended guidance was issued for an acquirer’s accounting for measurement-period adjustments. The amended guidance eliminates the requirement that an acquirer in a business combination account for measurement-period adjustments retrospectively and instead requires that measurement-period adjustments be recognized during the period in which it determines the adjustment. In addition, the amended guidance requires that the acquirer record, in the same period’s financial statements, the effect on earnings of changes in depreciation, amortization, or other income effects, if any, as a result of the change to the provisional amounts, calculated as if the accounting had been completed at the acquisition date. The amended guidance is effective for us prospectively commencing in the first quarter of 2017. Early adoption is permitted.

Inventory: In July 2015, amended guidance was issued for the subsequent measurement of inventory. The amended guidance requires entities to measure inventory at the lower of cost or net realizable value. Net realizable value is the estimated selling prices in the ordinary course of business, less reasonably predictable costs of completion, disposal, and transportation. The requirement would replace the current lower of cost or market evaluation. Accounting guidance is unchanged for inventory measured using last-in, first-out (“LIFO”) or the retail method. The amended guidance will become effective for us commencing in the first quarter of 2018. Early adoption is permitted. We are currently evaluating the impact of this amended guidance on our condensed consolidated financial statements.

Fair Value Measurement: In May 2015, amended guidance was issued that limits disclosures and removes the requirement to categorize investments within the fair value hierarchy if the fair value of the investment is measured using the net asset value per share practical expedient. The amended guidance will become effective for us retrospectively commencing in the first quarter of 2017. Early adoption is permitted. This amended guidance is primarily expected to affect our annual disclosures related to our pension benefits. We are currently evaluating the impact of this amended guidance on our condensed consolidated financial statements.

Fees Paid in a Cloud Computing Arrangement: In April 2015, amended guidance was issued for a customer’s accounting for fees paid in a cloud computing arrangement. The amended guidance requires customers to determine whether or not an arrangement contains a software license element. If the arrangement contains a software element, the related fees paid should be accounted for as an acquisition of a software license. If the arrangement does not contain a software license, it is accounted for as a service contract. The amended guidance will become effective for us commencing in the first quarter of 2017. Early adoption is permitted. We are currently evaluating the impact of this amended guidance on our condensed consolidated financial statements.

Debt Issuance Costs: In April 2015, amended guidance was issued for the balance sheet presentation of debt issuance costs. The amended guidance requires debt issuance costs related to a recognized debt liability to be reported on the balance sheet as a direct deduction from the carrying amount of that debt liability. The recognition and measurement guidance for debt issuance costs is not affected by the amended guidance. In August 2015, a clarification was added to this amended guidance that debt issuance costs related to line-of-credit arrangements can continue to be deferred and presented as an asset on the balance sheet. The amended guidance will become effective for us commencing in the first quarter of 2017. Early adoption is permitted. The amended guidance will affect financial statement presentation only and therefore we do not expect the adoption of this guidance to have a material effect on our condensed consolidated financial statements.

Consolidation: In February 2015, amended guidance was issued for consolidating legal entities in which a reporting entity holds a variable interest. The amended guidance modifies the evaluation of whether limited partnerships and similar legal entities are VIEs and changes the consolidation analysis of reporting entities that are involved with VIEs that have fee arrangements and related party relationships. The amended guidance will become effective for us commencing in the first quarter of 2017. Early adoption is permitted. We are currently evaluating the impact of this amended guidance on our condensed consolidated financial statements.

Revenue Recognition: In May 2014, amended guidance was issued for recognizing revenue from contracts with customers. The amended guidance eliminates industry specific guidance and applies to all companies. Revenues will be recognized when an entity satisfies a performance obligation by transferring control of a promised good or service to a customer in an amount that reflects the consideration to which the entity expects to be entitled for that good or service. Revenue from a contract that contains multiple performance obligations is allocated to each performance obligation generally on a relative standalone selling price basis. The amended guidance also requires additional quantitative and qualitative disclosures. In August 2015, additional guidance was issued to defer the effective date of the amended revenue recognition guidance by one year. As a result, the amended guidance is effective for us commencing in the first quarter of 2019. The amended guidance allows for either full retrospective adoption or modified retrospective adoption. Early adoption is permitted but not prior to our first quarter of 2018. We are currently evaluating the impact of this amended guidance on our condensed consolidated financial statements.