Healthcare Technology Net Asset Exchange	12 Months Ended
Mar. 31, 2019
Equity Method Investments and Joint Ventures [Abstract]
Healthcare Technology Net Asset Exchange	Healthcare Technology Net Asset Exchange In the fourth quarter of 2017, we contributed the majority of our McKesson Technology Solutions businesses (“Core MTS Business”) to the newly formed joint venture, Change Healthcare, under the terms of a contribution agreement previously entered into between McKesson and Change Healthcare Inc. (“Change”, formerly known as Change Healthcare Holdings, Inc.) and others including shareholders of Change. In exchange for the contribution, we own 70% of the joint venture with the remaining equity ownership held by shareholders of Change. The joint venture is jointly governed by us and shareholders of Change. Change Healthcare Inc., the entity that owns 30% of the joint venture, filed a registration statement with the Securities and Exchange Commission on March 15, 2019 and amended on April 5, 2019 regarding its intent to pursue an initial public offering. 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 2017, we deconsolidated the Core MTS Business and recorded a pre-tax gain of $3.9 billion (after-tax gain of $3.0 billion) in operating expenses. Additionally, in 2018, we recorded a pre-tax gain of $37 million (after-tax gain of $22 million) in operating expenses upon the finalization of net working capital and other adjustments. During 2018, we received $126 million in cash from Change Healthcare representing the final settlement of the net working capital and other adjustments. 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 recorded our proportionate share of loss from Change Healthcare of $194 million and $248 million in 2019 and 2018, which included transaction and integration expenses incurred by the joint venture and basis differences between the joint venture and McKesson including amortization of fair value adjustments primarily representing incremental intangible amortization and removal of profit associated with the recognition of deferred revenue. The proportionate share of loss from Change Healthcare recorded in 2018, was partially offset by a provisional tax benefit of $76 million recognized by Change Healthcare primarily due to a reduction in the future applicable tax rate related to the December 2017 enactment of the 2017 Tax Act. These amounts were recorded under the caption, “Loss from Equity Method Investment in Change Healthcare,” in our consolidated statement of operations. At March 31, 2019 and 2018, our carrying value of this equity method investment was $3,513 million and $3,728 million, which exceeded our proportionate share of the joint venture’s book value of net assets by approximately $4,158 million and $4,472 million, primarily reflecting equity method intangible assets and goodwill. Related Party Transactions In connection with the transaction, McKesson, Change Healthcare and certain shareholders of Change entered into various ancillary agreements, including transition services agreements (“TSA”), a transaction and advisory fee agreement (“Advisory Agreement”) and certain other commercial agreements. Fees incurred or earned from Advisory Agreement were not material for 2019 and 2018. Fees incurred or earned from TSA were $60 million in 2019, $91 million in 2018 and not material in 2017. Transition service fees are included within operating expenses in our consolidated statements of operations. Revenues recognized and expenses incurred under commercial arrangements with Change Healthcare were not material during 2019, 2018 and 2017. At March 31, 2019 and 2018, receivables due from the joint venture were not material. Tax Receivable Agreement In connection with the net asset exchange transaction, we also entered into a tax receivable agreement (“TRA”) with the shareholders of Change. At March 31, 2018, we had a $90 million noncurrent liability payable to the shareholders of Change. During 2019, we renegotiated the terms of the TRA which resulted in the extinguishment and derecognition of the $90 million noncurrent liability. In exchange for the shareholders of Change agreeing to extinguish the liability, we agreed to an allocation of certain tax amortization that had the effect of reducing the amount of a distribution from the Change Healthcare joint venture that would otherwise have been required to be made to the shareholders of Change. As a result of the renegotiation, McKesson was relieved from any potential future obligations associated with the noncurrent liability and recognized a pre-tax credit of $90 million ($66 million after-tax) in operating expenses in the accompanying consolidated statement of operations in 2019. We had no outstanding payable balance to the shareholders of Change at March 31, 2019.

Healthcare Technology Net Asset Exchange

In the fourth quarter of 2017, we contributed the majority of our McKesson Technology Solutions businesses (“Core MTS Business”) to the newly formed joint venture, Change Healthcare, under the terms of a contribution agreement previously entered into between McKesson and Change Healthcare Inc. (“Change”, formerly known as Change Healthcare Holdings, Inc.) and others including shareholders of Change. In exchange for the contribution, we own 70% of the joint venture with the remaining equity ownership held by shareholders of Change. The joint venture is jointly governed by us and shareholders of Change.

Change Healthcare Inc., the entity that owns 30% of the joint venture, filed a registration statement with the Securities and Exchange Commission on March 15, 2019 and amended on April 5, 2019 regarding its intent to pursue an initial public offering.

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 2017, we deconsolidated the Core MTS Business and recorded a pre-tax gain of $3.9 billion (after-tax gain of $3.0 billion) in operating expenses. Additionally, in 2018, we recorded a pre-tax gain of $37 million (after-tax gain of $22 million) in operating expenses upon the finalization of net working capital and other adjustments. During 2018, we received $126 million in cash from Change Healthcare representing the final settlement of the net working capital and other adjustments.

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 recorded our proportionate share of loss from Change Healthcare of $194 million and $248 million in 2019 and 2018, which included transaction and integration expenses incurred by the joint venture and basis differences between the joint venture and McKesson including amortization of fair value adjustments primarily representing incremental intangible amortization and removal of profit associated with the recognition of deferred revenue. The proportionate share of loss from Change Healthcare recorded in 2018, was partially offset by a provisional tax benefit of $76 million recognized by Change Healthcare primarily due to a reduction in the future applicable tax rate related to the December 2017 enactment of the 2017 Tax Act. These amounts were recorded under the caption, “Loss from Equity Method Investment in Change Healthcare,” in our consolidated statement of operations.

At March 31, 2019 and 2018, our carrying value of this equity method investment was $3,513 million and $3,728 million, which exceeded our proportionate share of the joint venture’s book value of net assets by approximately $4,158 million and $4,472 million, primarily reflecting equity method intangible assets and goodwill.

Related Party Transactions

In connection with the transaction, McKesson, Change Healthcare and certain shareholders of Change entered into various ancillary agreements, including transition services agreements (“TSA”), a transaction and advisory fee agreement (“Advisory Agreement”) and certain other commercial agreements. Fees incurred or earned from Advisory Agreement were not material for 2019 and 2018. Fees incurred or earned from TSA were $60 million in 2019, $91 million in 2018 and not material in 2017. Transition service fees are included within operating expenses in our consolidated statements of operations. Revenues recognized and expenses incurred under commercial arrangements with Change Healthcare were not material during 2019, 2018 and 2017. At March 31, 2019 and 2018, receivables due from the joint venture were not material.

Tax Receivable Agreement

In connection with the net asset exchange transaction, we also entered into a tax receivable agreement (“TRA”) with the shareholders of Change. At March 31, 2018, we had a $90 million noncurrent liability payable to the shareholders of Change. During 2019, we renegotiated the terms of the TRA which resulted in the extinguishment and derecognition of the $90 million noncurrent liability. In exchange for the shareholders of Change agreeing to extinguish the liability, we agreed to an allocation of certain tax amortization that had the effect of reducing the amount of a distribution from the Change Healthcare joint venture that would otherwise have been required to be made to the shareholders of Change. As a result of the renegotiation, McKesson was relieved from any potential future obligations associated with the noncurrent liability and recognized a pre-tax credit of $90 million ($66 million after-tax) in operating expenses in the accompanying consolidated statement of operations in 2019. We had no outstanding payable balance to the shareholders of Change at March 31, 2019.