Equity Method Investment in Change Healthcare Joint Venture	3 Months Ended
	Jun. 30, 2019
Equity Method Investments and Joint Ventures [Abstract]
Equity Method Investment in Change Healthcare Joint Venture	Equity Method Investment in Change Healthcare Joint Venture In the fourth quarter of 2017, we contributed the majority of our McKesson Technology Solutions businesses to form a joint venture, Change Healthcare LLC (“Change Healthcare JV”), under a contribution agreement between McKesson and Change Healthcare Inc. and others, including shareholders of Change Healthcare Inc. In exchange for the contribution, we initially owned approximately 70% of the joint venture with the remaining equity ownership of approximately 30% held by Change Healthcare Inc. The Change Healthcare JV is jointly governed by McKesson and shareholders of Change Healthcare Inc. The initial investment in Change Healthcare JV represented the fair value of our 70% equity interest in the joint venture upon closing of the transaction. We account for our investment in Change Healthcare JV using the equity method of accounting with a one-month reporting lag. The Company’s accounting policy is to disclose any intervening events of the joint venture in the lag period that could materially affect our condensed consolidated financial statements. Effective April 1, 2019, Change Healthcare JV adopted the amended revenue recognition guidance. In the first quarter of 2020, we recorded our proportionate share of the joint venture’s adoption impact of the amended revenue recognition guidance of approximately $80 million, net of tax to the opening retained earnings. During the first quarters of 2020 and 2019, we recorded our proportionate share of income of $4 million and loss of $56 million from Change Healthcare JV. Our proportionate share of income or loss from this equity method investment includes integration expenses incurred by Change Healthcare JV and basis differences between the joint venture and McKesson including amortization of fair value adjustments primarily representing incremental intangible assets. These amounts were recorded under the caption, “Income (Loss) from Equity Method Investment in Change Healthcare Joint Venture,” in our condensed consolidated statements of operations. At June 30, 2019 and March 31, 2019, our carrying value of this equity method investment was $3,617 million and $3,513 million. Our carrying value included equity method intangible assets and goodwill which caused our investment basis to exceed our proportionate share of the Change Healthcare JV’s book value of net assets by approximately $4,091 million and $4,158 million at June 30, 2019 and March 31, 2019. Initial Public Offering by Change Healthcare Inc. On June 27, 2019, common stock and certain other securities of Change Healthcare Inc. began trading on the NASDAQ (“IPO”). Change Healthcare Inc. is a holding company and does not own any material assets or have any operations other than through its interest in Change Healthcare JV. On July 1, 2019, upon the completion of its IPO, Change Healthcare Inc. received net cash proceeds of approximately $888 million. Change Healthcare Inc. contributed the proceeds from its offering of common stock of $609 million to Change Healthcare JV in exchange for additional membership interests of Change Healthcare JV (“LLC Units”) at the equivalent of its offering price of $13 per share. The proceeds from the concurrent offering of other securities of $279 million were used by Change Healthcare Inc. to acquire certain securities of Change Healthcare JV that substantially mirror the terms of other securities included in the offering by Change Healthcare Inc. Change Healthcare JV, in return, used the majority of the IPO proceeds to repay a portion of the joint venture’s outstanding debt. As a result, McKesson’s equity interest in Change Healthcare JV diluted from approximately 70% to approximately 58.5% and Change Healthcare Inc. now owns approximately 41.5% of the outstanding LLC Units. Accordingly, in the second quarter of 2020, we expect to recognize a pre-tax dilution loss of approximately $246 million associated with our reduction of our ownership in the Change Healthcare JV. The loss represents the difference between our proportionate share of the IPO proceeds and the dilution effect on our investment’s carrying value. Effective with the second quarter of 2020, we will recognize our proportionate share in net income or loss based on our reduced share of equity interest in Change Healthcare JV, adjusted for the effect of basis differences and other items as applicable. Subsequent to the IPO, we now have a publicly available indication of the value of our investment in Change Healthcare JV. The fair value that was derived from trading prices of Change Healthcare Inc.’s common stock was below the carrying value of our investment in Change Healthcare JV indicating a potential impairment. Accordingly, we evaluated our equity method investment for an other-than-temporary impairment (“OTTI”). We considered various factors in determining whether an OTTI has occurred, including the limited trading history available, our ability and intent to hold the investment until its fair value recovers, the implied EBITDA valuation multiples compared to public guideline companies, the joint venture’s ability to achieve milestones and any notable operational and strategic changes by the joint venture. After the evaluation, we determined that an OTTI has not occurred as of June 30, 2019 and as of the date of this Quarterly Report on Form 10-Q. However, we may be required to recognize an impairment loss in future reporting periods if and when a decline in fair value of our investment in Change Healthcare JV below the carrying value is determined to be other than temporary. Such determination will be based on the prevailing facts and circumstances at that time, including the reported results and disclosures of Change Healthcare Inc. as well as the market price of its common stock. Related Party Transactions In connection with the formation of Change Healthcare JV, McKesson, Change Healthcare JV and certain shareholders of Change Healthcare Inc. 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 agreements. Fees incurred or earned from TSA and Advisory Agreement were not material to us during the first quarters of 2020 and 2019. At June 30, 2019 and March 31, 2019, we had no outstanding payable balance to the shareholders of Change Healthcare Inc. under the TRA. Revenues recognized, and expenses incurred under these agreements with Change Healthcare JV were not material during the first quarters of 2020 and 2019. At June 30, 2019 and March 31, 2019, receivables due from the joint venture were not material. Concurrent with the IPO, Change Healthcare Inc. appointed two of our current executive officers and our former chief executive officer to its Board of Directors. These appointments had no impact on the equity method of accounting we apply to our investment in Change Healthcare JV. There were no material transactions with Change Healthcare Inc.