Fair Value Measurements	3 Months Ended
Fair Value Measurements	Jun. 30, 2018
Fair Value Disclosures [Abstract]
Fair Value Measurements	Fair Value Measurements At June 30, 2018 and March 31, 2018, the carrying amounts of cash, certain cash equivalents, restricted cash, marketable securities, receivables, drafts and accounts payable, short-term borrowings and other current liabilities approximated their estimated fair values because of the short maturity of these financial instruments. The fair value of our commercial paper was determined using quoted prices in active markets for identical liabilities, which are considered Level 1 inputs. Our long-term debt is carried at amortized cost. The carrying amounts and estimated fair values of these liabilities were $7.7 billion and $7.8 billion at June 30, 2018, and $7.9 billion and $8.1 billion at March 31, 2018. The estimated fair value of our long-term debt was determined using quoted market prices in a less active market and other observable inputs from available market information, which are considered to be Level 2 inputs, and may not be representative of actual values that could have been realized or that will be realized in the future. Assets Measured at Fair Value on a Recurring Basis Cash and cash equivalents at June 30, 2018 and March 31, 2018 included investments in money market funds of $165 million and $799 million, which are reported at fair value. The fair value of the money market funds was determined by using quoted prices for identical investments in active markets, which are considered to be Level 1 inputs under the fair value measurements and disclosure guidance. The carrying value of all other cash equivalents approximates their fair value due to their relatively short-term nature. Fair values of our forward foreign currency contracts were determined using observable inputs from available market information. Fair values of our cross-currency swaps were determined using quoted foreign currency exchange rates and other observable inputs from available market information. These inputs are considered Level 2 under the fair value measurements and disclosure guidance, and may not be representative of actual values that could have been realized or that will be realized in the future. Refer to Financial Note 12, “Hedging Activities,” for fair value and other information on our foreign currency derivatives including forward foreign currency contracts and cross-currency swaps. There were no transfers between Level 1, Level 2 or Level 3 of the fair value hierarchy during the quarter ended June 30, 2018. Assets Measured at Fair Value on a Nonrecurring Basis At June 30, 2018, assets measured at fair value on a nonrecurring basis consisted of goodwill and intangible assets for two reporting units within our European Pharmaceutical Solutions segment. Refer to Financial Note 3, “Goodwill Impairment Charges,” and Financial Note 5, “Restructuring and Asset Impairment Charges” for more information. At March 31, 2018, assets measured at fair value on a nonrecurring basis consisted of goodwill, intangible and other long-lived assets for our McKesson Europe and Rexall Health reporting units within our former Distribution Solutions segment, which existed prior to the 2019 first quarter realignment in our operating segment structure. Goodwill Fair value assessments of the reporting unit and the reporting unit's net assets, which are performed for goodwill impairment tests, are considered a Level 3 measurement due to the significance of unobservable inputs developed using company-specific information. We considered a market approach as well as an income approach using the DCF model to determine the fair value of the reporting unit. Intangible Assets We utilized a combination of an income approach and a market approach for estimating the fair value of intangible assets. The future cash flows used in the analysis are based on internal cash flow projections based on our long-range plans and include significant assumptions by management. Accordingly, the fair value assessment of the long-lived assets is considered a Level 3 fair value measurement. Liabilities Measured at Fair Value on a Nonrecurring Basis At June 30, 2018 and March 31, 2018, we remeasured the contingent consideration liability related to our April 2018 acquisition of CMM at fair value on a nonrecurring basis. Refer to Financial Note 4, “Business Combinations” for more information on the fair value of the contingent consideration liability.

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.