Healthcare Technology Net Asset Exchange	12 Months Ended
Mar. 31, 2017
Equity Method Investments and Joint Ventures [Abstract]
Healthcare Technology Net Asset Exchange	Healthcare Technology Net Asset Exchange On June 28, 2016, we entered into a contribution agreement (“Contribution Agreement”) with Change Healthcare Holdings, Inc. (“Change”), a Delaware corporation, and others including shareholders of Change to form a joint venture, Change Healthcare, LLC (“Change Healthcare”), a Delaware limited liability company. On December 21, 2016, we received notification from the Department of Justice that their review was closed and the waiting period under the Hart-Scott-Rodino Antitrust Improvements Act of 1976, as amended, was terminated. On March 1, 2017, the transaction closed upon satisfaction of all other closing conditions pursuant to the Contribution Agreement. Under the terms of the Contribution Agreement, we contributed the majority of our McKesson Technology Solutions businesses (“Core MTS Business”) to the newly formed joint venture, Change Healthcare. We retained our RelayHealth Pharmacy and Enterprise Information Solutions (“EIS”) businesses. Change contributed substantially all of its businesses to the joint venture excluding its pharmacy switch and prescription routing business. In exchange for the contribution, we own 70% of the joint venture with the remaining equity ownership held by Change shareholders. The joint venture is jointly governed by us and Change shareholders. Change Healthcare is a healthcare technology company which provides software and analytics, network solutions and technology-enabled services that will deliver wide-ranging financial, operational and clinical benefits to payers, providers and consumers. In connection with the closing of the transaction, Change Healthcare issued long-term debt of $6.1 billion, which was utilized to fund cash payments for our promissory notes (as described below) and approximately $1.75 billion to Change stockholders, to cover transaction costs and to repay approximately $2.8 billion of existing Change’s debt. McKesson and Change shareholders have agreed to take steps to launch an initial public offering of an entity which holds equity in Change Healthcare, subject to market conditions. Sometime thereafter, we expect to exit our investment in Change Healthcare through a distribution to McKesson shareholders. Gain from Healthcare Technology Net Asset Exchange We accounted for this transaction as a sale of the Core MTS Business and a subsequent purchase of a 70% interest in the newly formed joint venture. Accordingly, in the fourth quarter of 2017, we deconsolidated the Core MTS Business and recorded a pre-tax gain of $3,947 million (after-tax gain of $3,018 million). The pre-tax gain was calculated based on the difference between the fair value of our 70% equity interest in the joint venture, less the carrying amount of the contributed Core MTS Business’ net assets of $1,132 million and $1,258 million of promissory notes, a $136 million noncurrent liability associated with a tax receivable agreement (as described below) and transaction and other related expenses. The $1,258 million of promissory notes were subsequently repaid in cash from proceeds of Change Healthcare’s long term debt issuance. The gain is subject to final net working capital and other adjustments within 90 days from the transaction close date, and is included under the caption “Gain from Healthcare Technology Net Asset Exchange, net” within operating expenses in our consolidated statements of operations. This transaction did not meet the criteria to be reported as a discontinued operation since it did not constitute a significant strategic business shift for the Company. The fair value of the joint venture was determined using a combination of the income and the market valuation approaches. Under the income approach, we used a discounted cash flow model (“DCF”) in which cash flows anticipated over several periods, plus a terminal value at the end of that time horizon, are discounted to their present value using an appropriate expected rate of return. The discount rate used for cash flows reflects capital market conditions and the specific risks associated with the business. Under the market approach, valuation multiples of reasonably similar publicly traded companies or guideline companies are applied to the operating data of the subject business to derive the estimated fair value. These valuation approaches are considered a Level 3 fair value measurement. Fair value determination requires complex assumptions and judgment by management in projecting future operating results, selecting guideline companies for comparisons, determining appropriate market value multiples, selecting the discount rate to measure the risks inherent in the future cash flows and assessing the asset’s life cycle and the competitive trends impacting the assets, including considering technical, legal, regulatory, or economic barriers to entry. Any material changes in key assumptions, including failure to meet business plans, deterioration in the financial market, an increase in interest rate or an increase in the cost of equity financing by market participants within the industry or other unanticipated events and circumstances, may affect such estimates. Equity Method Investment in Change Healthcare Our investment in the joint venture is accounted for using the equity method of accounting on a one-month reporting lag. We disclose intervening events at the joint venture in the lag period that could materially affect our consolidated financial statements, if applicable. In March 2017, our proportionate share of transaction expenses incurred by the joint venture is estimated to be approximately $80 million to $120 million. However, due to the timing of the transaction and the one-month reporting lag, no net income or loss from our investment was recorded in our financial results for 2017. Commencing April 1, 2017, our proportionate share of the net income or loss from the joint venture including these transaction expenses will be recorded in “Other Income, Net” in our consolidated statement of operations. At March 31, 2017, our carrying value in our investment was $4,063 million, which exceeded our proportionate share of the joint venture’s book value of net assets by approximately $4,762 million, primarily reflecting equity method intangible and goodwill assets and other fair value adjustments including a non-cash reduction to the carrying value of deferred revenue. Agreements with Change Healthcare and Related Party Transactions At the closing of the transaction, McKesson, Change Healthcare and certain Change shareholders also entered into various ancillary agreements, including transition services agreements (“TSA”), a transaction and advisory fee agreement (“Advisory Agreement”), a tax receivable agreement (“TRA”) and certain other commercial agreements. Pursuant to the TSA, McKesson provides various transitional services to the joint venture to support certain operations including information technology, accounting and other administrative services. The total fees charged by us for such transition services were immaterial for 2017. Transition services fees are included under the caption “Selling, distribution and administrative expenses” in our consolidated statements of operations. Pursuant to the Advisory Agreement, the joint venture will pay McKesson and Change shareholders an agreed upon amount for each fiscal year on a quarterly basis. Additionally, McKesson and Change are entitled to receive transaction fees equal to 1% of the aggregate transaction value upon the consummation of any acquisition, divestiture, disposition, merger, consolidation, business combination, change of control, restructuring, reorganization or recapitalization, financing or refinancing or issuance of securities. The foregoing advisory and transaction fees are non-refundable and allocated to McKesson and Change shareholders based on their respective equity ownership percentages. In 2017, we did not earn material advisory fees and transaction fees. Pursuant to the TRA, McKesson may be required to make certain payments or may be entitled to receive certain payments related to the cash tax savings attributable to the utilization of certain tax attributes, including certain amortizable tax basis in software contributed by McKesson to Change Healthcare. At March 31, 2017, we have recorded a $136 million noncurrent liability payable to Change Healthcare shareholders associated with the TRA. The amount is based on certain estimates and could become payable in periods after a disposition of our investment in Change Healthcare. No such payments were required to be made or received for 2017. Revenues recorded and expenses incurred under commercial arrangements with Change Healthcare were not material during 2017. At March 31, 2017, receivables from and payables to the joint venture were not material.

Healthcare Technology Net Asset Exchange

On June 28, 2016, we entered into a contribution agreement (“Contribution Agreement”) with Change Healthcare Holdings, Inc. (“Change”), a Delaware corporation, and others including shareholders of Change to form a joint venture, Change Healthcare, LLC (“Change Healthcare”), a Delaware limited liability company. On December 21, 2016, we received notification from the Department of Justice that their review was closed and the waiting period under the Hart-Scott-Rodino Antitrust Improvements Act of 1976, as amended, was terminated. On March 1, 2017, the transaction closed upon satisfaction of all other closing conditions pursuant to the Contribution Agreement. Under the terms of the Contribution Agreement, we contributed the majority of our McKesson Technology Solutions businesses (“Core MTS Business”) to the newly formed joint venture, Change Healthcare. We retained our RelayHealth Pharmacy and Enterprise Information Solutions (“EIS”) businesses. Change contributed substantially all of its businesses to the joint venture excluding its pharmacy switch and prescription routing business. In exchange for the contribution, we own 70% of the joint venture with the remaining equity ownership held by Change shareholders. The joint venture is jointly governed by us and Change shareholders. Change Healthcare is a healthcare technology company which provides software and analytics, network solutions and technology-enabled services that will deliver wide-ranging financial, operational and clinical benefits to payers, providers and consumers.

In connection with the closing of the transaction, Change Healthcare issued long-term debt of $6.1 billion, which was utilized to fund cash payments for our promissory notes (as described below) and approximately $1.75 billion to Change stockholders, to cover transaction costs and to repay approximately $2.8 billion of existing Change’s debt.

McKesson and Change shareholders have agreed to take steps to launch an initial public offering of an entity which holds equity in Change Healthcare, subject to market conditions. Sometime thereafter, we expect to exit our investment in Change Healthcare through a distribution to McKesson shareholders.

Gain from Healthcare Technology Net Asset Exchange

We accounted for this transaction as a sale of the Core MTS Business and a subsequent purchase of a 70% interest in the newly formed joint venture. Accordingly, in the fourth quarter of 2017, we deconsolidated the Core MTS Business and recorded a pre-tax gain of $3,947 million (after-tax gain of $3,018 million). The pre-tax gain was calculated based on the difference between the fair value of our 70% equity interest in the joint venture, less the carrying amount of the contributed Core MTS Business’ net assets of $1,132 million and $1,258 million of promissory notes, a $136 million noncurrent liability associated with a tax receivable agreement (as described below) and transaction and other related expenses. The $1,258 million of promissory notes were subsequently repaid in cash from proceeds of Change Healthcare’s long term debt issuance. The gain is subject to final net working capital and other adjustments within 90 days from the transaction close date, and is included under the caption “Gain from Healthcare Technology Net Asset Exchange, net” within operating expenses in our consolidated statements of operations. This transaction did not meet the criteria to be reported as a discontinued operation since it did not constitute a significant strategic business shift for the Company.

The fair value of the joint venture was determined using a combination of the income and the market valuation approaches. Under the income approach, we used a discounted cash flow model (“DCF”) in which cash flows anticipated over several periods, plus a terminal value at the end of that time horizon, are discounted to their present value using an appropriate expected rate of return. The discount rate used for cash flows reflects capital market conditions and the specific risks associated with the business. Under the market approach, valuation multiples of reasonably similar publicly traded companies or guideline companies are applied to the operating data of the subject business to derive the estimated fair value. These valuation approaches are considered a Level 3 fair value measurement. Fair value determination requires complex assumptions and judgment by management in projecting future operating results, selecting guideline companies for comparisons, determining appropriate market value multiples, selecting the discount rate to measure the risks inherent in the future cash flows and assessing the asset’s life cycle and the competitive trends impacting the assets, including considering technical, legal, regulatory, or economic barriers to entry. Any material changes in key assumptions, including failure to meet business plans, deterioration in the financial market, an increase in interest rate or an increase in the cost of equity financing by market participants within the industry or other unanticipated events and circumstances, may affect such estimates.

Equity Method Investment in Change Healthcare

Our investment in the joint venture is accounted for using the equity method of accounting on a one-month reporting lag. We disclose intervening events at the joint venture in the lag period that could materially affect our consolidated financial statements, if applicable. In March 2017, our proportionate share of transaction expenses incurred by the joint venture is estimated to be approximately $80 million to $120 million. However, due to the timing of the transaction and the one-month reporting lag, no net income or loss from our investment was recorded in our financial results for 2017. Commencing April 1, 2017, our proportionate share of the net income or loss from the joint venture including these transaction expenses will be recorded in “Other Income, Net” in our consolidated statement of operations.

At March 31, 2017, our carrying value in our investment was $4,063 million, which exceeded our proportionate share of the joint venture’s book value of net assets by approximately $4,762 million, primarily reflecting equity method intangible and goodwill assets and other fair value adjustments including a non-cash reduction to the carrying value of deferred revenue.

Agreements with Change Healthcare and Related Party Transactions

At the closing of the transaction, McKesson, Change Healthcare and certain Change shareholders also entered into various ancillary agreements, including transition services agreements (“TSA”), a transaction and advisory fee agreement (“Advisory Agreement”), a tax receivable agreement (“TRA”) and certain other commercial agreements.

Pursuant to the TSA, McKesson provides various transitional services to the joint venture to support certain operations including information technology, accounting and other administrative services. The total fees charged by us for such transition services were immaterial for 2017. Transition services fees are included under the caption “Selling, distribution and administrative expenses” in our consolidated statements of operations.

Pursuant to the Advisory Agreement, the joint venture will pay McKesson and Change shareholders an agreed upon amount for each fiscal year on a quarterly basis. Additionally, McKesson and Change are entitled to receive transaction fees equal to 1% of the aggregate transaction value upon the consummation of any acquisition, divestiture, disposition, merger, consolidation, business combination, change of control, restructuring, reorganization or recapitalization, financing or refinancing or issuance of securities. The foregoing advisory and transaction fees are non-refundable and allocated to McKesson and Change shareholders based on their respective equity ownership percentages. In 2017, we did not earn material advisory fees and transaction fees.

Pursuant to the TRA, McKesson may be required to make certain payments or may be entitled to receive certain payments related to the cash tax savings attributable to the utilization of certain tax attributes, including certain amortizable tax basis in software contributed by McKesson to Change Healthcare. At March 31, 2017, we have recorded a $136 million noncurrent liability payable to Change Healthcare shareholders associated with the TRA. The amount is based on certain estimates and could become payable in periods after a disposition of our investment in Change Healthcare. No such payments were required to be made or received for 2017.

Revenues recorded and expenses incurred under commercial arrangements with Change Healthcare were not material during 2017. At March 31, 2017, receivables from and payables to the joint venture were not material.