Healthcare Technology Net Asset Exchange	9 Months Ended
Dec. 31, 2017
Equity Method Investments and Joint Ventures [Abstract]
Healthcare Technology Net Asset Exchange	Healthcare Technology Net Asset Exchange On March 1, 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 Holdings, Inc. (“Change”) and others including shareholders of Change. We retained our RelayHealth Pharmacy (“RHP”) and Enterprise Information Solutions (“EIS”) businesses. The EIS business was subsequently sold to a third party in the third quarter of 2018. 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. 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). Additionally, in the first quarter of 2018, we recorded a pre-tax gain of $37 million (after-tax gain of $22 million) in operating expenses in the accompanying condensed consolidated statement of operations upon the finalization of net working capital and other adjustments. During the second quarter of 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. During the third quarter and first nine months of 2018, we recorded our proportionate share of loss from Change Healthcare of $90 million and $271 million, which included transaction and integration expenses incurred by the joint venture and fair value adjustments including incremental intangible assets amortization associated with basis differences. This amount was recorded under the caption, “Loss from Equity Method Investment in Change Healthcare,” in our condensed consolidated statement of operations. As our investment is accounted for using a one-month lag, the effects of the enactment of the 2017 Tax Cuts and Jobs Act (the “2017 Tax Act”) are expected to be recognized in our condensed statement of operations in the fourth quarter of 2018. We expect our proportionate share of a provisional net benefit recognized by Change Healthcare from the enactment of the 2017 Tax Act to be approximately $70 million to $110 million primarily due to a reduction in future applicable tax rate. The impact of the 2017 Tax Act for Change Healthcare may differ materially from this provisional amount. At December 31, 2017, the carrying value of our investment was $3,704 million, which exceeded our proportionate share of the joint venture’s book value of net assets by approximately $4,526 million, primarily reflecting equity method intangible assets, goodwill and other fair value adjustments. 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”), a tax receivable agreement (“TRA”) and certain other commercial agreements. At March 31, 2017, we had a $136 million noncurrent liability payable to shareholders of Change associated with the TRA. At December 31, 2017, the amount was reduced to $90 million reflecting a reduction in future applicable tax rate under the 2017 Tax Act. The amount is based on certain estimates and could become payable in periods after a disposition of our investment in Change Healthcare. The total fees charged by us to the joint venture for various transition services under the TSA were $22 million and $69 million for the third quarter and first nine months of 2018. Transition services fees are included within operating expenses in our condensed consolidated statements of operations. During the third quarter and first nine months of 2018, we did not earn material transaction and advisory fees under the Advisory Agreement. Revenues recognized and expenses incurred under commercial arrangements with Change Healthcare were not material during the third quarter and first nine months of 2018. At December 31, 2017, receivables due from the joint venture were $54 million and at March 31, 2017, receivables due from the joint venture were not material.

Healthcare Technology Net Asset Exchange

On March 1, 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 Holdings, Inc. (“Change”) and others including shareholders of Change. We retained our RelayHealth Pharmacy (“RHP”) and Enterprise Information Solutions (“EIS”) businesses. The EIS business was subsequently sold to a third party in the third quarter of 2018. 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.

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). Additionally, in the first quarter of 2018, we recorded a pre-tax gain of $37 million (after-tax gain of $22 million) in operating expenses in the accompanying condensed consolidated statement of operations upon the finalization of net working capital and other adjustments. During the second quarter of 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. During the third quarter and first nine months of 2018, we recorded our proportionate share of loss from Change Healthcare of $90 million and $271 million, which included transaction and integration expenses incurred by the joint venture and fair value adjustments including incremental intangible assets amortization associated with basis differences. This amount was recorded under the caption, “Loss from Equity Method Investment in Change Healthcare,” in our condensed consolidated statement of operations.

As our investment is accounted for using a one-month lag, the effects of the enactment of the 2017 Tax Cuts and Jobs Act (the “2017 Tax Act”) are expected to be recognized in our condensed statement of operations in the fourth quarter of 2018. We expect our proportionate share of a provisional net benefit recognized by Change Healthcare from the enactment of the 2017 Tax Act to be approximately $70 million to $110 million primarily due to a reduction in future applicable tax rate. The impact of the 2017 Tax Act for Change Healthcare may differ materially from this provisional amount.

At December 31, 2017, the carrying value of our investment was $3,704 million, which exceeded our proportionate share of the joint venture’s book value of net assets by approximately $4,526 million, primarily reflecting equity method intangible assets, goodwill and other fair value adjustments.

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”), a tax receivable agreement (“TRA”) and certain other commercial agreements.

At March 31, 2017, we had a $136 million noncurrent liability payable to shareholders of Change associated with the TRA. At December 31, 2017, the amount was reduced to $90 million reflecting a reduction in future applicable tax rate under the 2017 Tax Act. The amount is based on certain estimates and could become payable in periods after a disposition of our investment in Change Healthcare.

The total fees charged by us to the joint venture for various transition services under the TSA were $22 million and $69 million for the third quarter and first nine months of 2018. Transition services fees are included within operating expenses in our condensed consolidated statements of operations.

During the third quarter and first nine months of 2018, we did not earn material transaction and advisory fees under the Advisory Agreement.

Revenues recognized and expenses incurred under commercial arrangements with Change Healthcare were not material during the third quarter and first nine months of 2018.

At December 31, 2017, receivables due from the joint venture were $54 million and at March 31, 2017, receivables due from the joint venture were not material.