Goodwill Impairment Charges	12 Months Ended
Mar. 31, 2019
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill Impairment Charges	Goodwill Impairment Charges We evaluate goodwill for impairment on an annual basis as of January 1 each year and at an interim date, if indicators of potential impairment exist. Goodwill impairment testing is conducted at the reporting unit level, which is generally defined as an operating segment or one level below an operating segment (also known as a component), for which discrete financial information is available and segment management regularly reviews the operating results of that reporting unit. The fair value of the reporting unit was determined using a combination of an income approach based on a DCF model and a market approach based on appropriate valuation multiples observed for the reporting unit’s guideline public companies. Fair value estimates result from a complex series of judgments about future events and uncertainties and rely heavily on estimates and assumptions that have been deemed reasonable by management as of the measurement date. Any material changes in key assumptions, including failure to improve operations of certain retail pharmacy stores, additional government reimbursement reductions, deterioration in the financial markets, an increase in interest rates 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. The discount rates are the weighted average cost of capital measuring the reporting unit’s cost of debt and equity financing weighted by the percentage of debt and percentage of equity in a company’s target capital. The unsystematic risk premium is an input factor used in calculating discount rate that specifically addresses uncertainty related to the reporting unit’s future cash flow projections. Fair value assessments of the reporting unit are considered a Level 3 measurement due to the significance of unobservable inputs developed using company specific information. In 2019, we recorded total non-cash pre-tax goodwill impairment charges of $1,776 million ($1,756 million after-tax) for our two reporting units in our European Pharmaceutical Solutions segment. In 2018, we recorded non-cash goodwill impairment charges of $1,283 million (pre-tax and after-tax) in our European Pharmaceutical Solutions segment and $455 million (pre-tax and after-tax) for our Rexall Health reporting unit included in Other. In 2017, we recorded a non-cash pre-tax goodwill impairment charge of $290 million ($282 million after-tax) for our Enterprise Information Solutions (“EIS”) reporting unit included in Other. These charges were recorded under the caption, “Goodwill Impairment Charges” within operating expenses in the accompanying consolidated statements of operations. Most of the goodwill impairment for these reporting units were generally not deductible for income tax purposes. McKesson Europe: Fiscal 2019 In 2019, we recorded total non-cash pre-tax charges of $1,776 million ($1,756 million after-tax) to impair the carrying value of goodwill for our Consumer Solutions (“CS”) and Pharmacy Solutions (“PS”) reporting units in our European Pharmaceutical Solutions segment. Prior to implementing the new segment reporting structure in the first quarter of 2019, our European operations were considered a single reporting unit. Following the change in reportable segments, our European Pharmaceutical Solutions segment was split into two distinct reporting units, CS and PS, for the purposes of goodwill impairment testing. As a result, we were required to perform a goodwill impairment test for these two new reporting units upon the change in reportable segment. Consequently, we recorded a non-cash goodwill impairment charge of $238 million (pre-tax and after-tax) in the first quarter of 2019 because the estimated fair value of the PS reporting unit was determined to be lower than its reassigned carrying value. In the first quarter of 2019, both CS and PS reporting units projected a decline in the estimated future cash flows primarily triggered by additional U.K. government actions which were announced on June 29, 2018. Accordingly, we performed an interim goodwill impairment test for these reporting units. As a result, we determined that the carrying values of these reporting units exceeded their estimated fair value and recorded non-cash goodwill impairment charges of $332 million (pre-tax and after-tax) primarily for our CS reporting unit. The discount rate and terminal growth rate used for the CS reporting unit in the first quarter 2019 impairment test were 8.5% and 1.25%. The discount rate and terminal growth rate used for the PS reporting unit in the first quarter 2019 impairment test were 8.0% and 1.25%. In the fourth quarter of 2019, as a result of our annual goodwill impairment test, we determined that the carrying values of our CS and PS reporting units exceeded their estimated fair value and recorded non-cash charges of $465 million ($445 million after-tax) for the CS reporting unit and $741 million (pre-tax and after-tax) for the PS reporting unit. The additional impairments were primarily due to declines in the reporting units’ estimated future cash flows and the selection of higher discount rates. The declines in estimated future cash flows were primarily attributed to additional government reimbursement reductions and competitive pressures within the U.K. The risk of successfully achieving certain business initiatives was the primary factor in the use of a higher discount rate. The discount rate and terminal growth rate used for the CS reporting unit in our 2019 annual impairment test were 10.0% and 1.25%. The discount rate and terminal growth rate used for the PS reporting unit in our 2019 annual impairment test were 9.0% and 1.25%. At March 31, 2019, both CS and PS reporting units had no remaining goodwill balances. Fiscal 2018 In 2018, we recorded total non-cash charges of $1,283 million (pre-tax and after-tax) to impair the carrying value of goodwill within our European Pharmaceutical Solutions segment. During the second quarter of 2018, our former McKesson Europe reporting unit projected a decline in its estimated future cash flows primarily triggered by government reimbursement reductions in their retail business in the U.K. Accordingly, we performed an interim one-step goodwill impairment test in accordance with the amended goodwill guidance for this reporting unit prior to our annual impairment test. As a result of the interim impairment test, we determined that the carrying value of this reporting unit exceeded its estimated fair value and recorded a non-cash charge of $350 million (pre-tax and after-tax) to impair the carrying value of this reporting unit’s goodwill. The discount rate and terminal growth rate used in our 2018 second quarter impairment test were 7.5% and 1.25% compared to 7.0% and 1.5% in our 2017 annual impairment test. Additionally, as a result of our 2018 annual impairment test, we determined that the carrying value of the former McKesson Europe reporting unit further exceeded its estimated fair value and recorded a non-cash goodwill impairment charge of $933 million (pre-tax and after-tax) in the fourth quarter of 2018. This reporting unit had a further decline in its estimated future cash flows driven by weakening script growth outlook in our U.K. business and by a more competitive environment in France during the fourth quarter of 2018. The discount rate and terminal growth rate used in our 2018 annual impairment test were 8.0% and 1.25%. Rexall Health: Fiscal 2018 In 2018, as a result of our 2018 annual impairment test, we determined that the carrying value of our Rexall Health reporting unit within Other exceeded its estimated fair value and recorded a non-cash goodwill impairment charge of $455 million (pre-tax and after-tax). The impairment was the result of a decline in estimated future cash flows primarily driven by significant generics reimbursement reductions across Canada and minimum wage increases in multiple provinces which can only be partially mitigated through the business’ cost saving efforts. The discount rate and terminal growth rate used in our impairment testing for this reporting unit were 10.0% and 2.0%. At March 31, 2019 and 2018, the Rexall Health reporting unit had no remaining goodwill related to our acquisition of Rexall Health. Enterprise Information Solutions: Fiscal 2017 In conjunction with the 2017 Healthcare Technology Net Asset Exchange, we evaluated strategic options for our EIS business, which was a reporting unit within Other. In 2017, we recorded a non-cash pre-tax charge of $290 million ($282 million after-tax) to impair the carrying value of this reporting unit’s goodwill. The impairment primarily resulted from a decline in estimated cash flows. The amount of goodwill impairment for the EIS reporting unit was determined under the former accounting guidance on goodwill impairment testing, and computed as the excess of the carrying value of the reporting unit’s goodwill over its implied fair value of its goodwill. Refer to Financial Note 21, “Fair Value Measurements,” for more information on this nonrecurring fair value measurement.

Goodwill Impairment Charges

We evaluate goodwill for impairment on an annual basis as of January 1 each year and at an interim date, if indicators of potential impairment exist. Goodwill impairment testing is conducted at the reporting unit level, which is generally defined as an operating segment or one level below an operating segment (also known as a component), for which discrete financial information is available and segment management regularly reviews the operating results of that reporting unit.

The fair value of the reporting unit was determined using a combination of an income approach based on a DCF model and a market approach based on appropriate valuation multiples observed for the reporting unit’s guideline public companies. Fair value estimates result from a complex series of judgments about future events and uncertainties and rely heavily on estimates and assumptions that have been deemed reasonable by management as of the measurement date. Any material changes in key assumptions, including failure to improve operations of certain retail pharmacy stores, additional government reimbursement reductions, deterioration in the financial markets, an increase in interest rates 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. The discount rates are the weighted average cost of capital measuring the reporting unit’s cost of debt and equity financing weighted by the percentage of debt and percentage of equity in a company’s target capital. The unsystematic risk premium is an input factor used in calculating discount rate that specifically addresses uncertainty related to the reporting unit’s future cash flow projections. Fair value assessments of the reporting unit are considered a Level 3 measurement due to the significance of unobservable inputs developed using company specific information.

In 2019, we recorded total non-cash pre-tax goodwill impairment charges of $1,776 million ($1,756 million after-tax) for our two reporting units in our European Pharmaceutical Solutions segment. In 2018, we recorded non-cash goodwill impairment charges of $1,283 million (pre-tax and after-tax) in our European Pharmaceutical Solutions segment and $455 million (pre-tax and after-tax) for our Rexall Health reporting unit included in Other. In 2017, we recorded a non-cash pre-tax goodwill impairment charge of $290 million ($282 million after-tax) for our Enterprise Information Solutions (“EIS”) reporting unit included in Other. These charges were recorded under the caption, “Goodwill Impairment Charges” within operating expenses in the accompanying consolidated statements of operations. Most of the goodwill impairment for these reporting units were generally not deductible for income tax purposes.

McKesson Europe:

Fiscal 2019

In 2019, we recorded total non-cash pre-tax charges of $1,776 million ($1,756 million after-tax) to impair the carrying value of goodwill for our Consumer Solutions (“CS”) and Pharmacy Solutions (“PS”) reporting units in our European Pharmaceutical Solutions segment.

Prior to implementing the new segment reporting structure in the first quarter of 2019, our European operations were considered a single reporting unit. Following the change in reportable segments, our European Pharmaceutical Solutions segment was split into two distinct reporting units, CS and PS, for the purposes of goodwill impairment testing. As a result, we were required to perform a goodwill impairment test for these two new reporting units upon the change in reportable segment. Consequently, we recorded a non-cash goodwill impairment charge of $238 million (pre-tax and after-tax) in the first quarter of 2019 because the estimated fair value of the PS reporting unit was determined to be lower than its reassigned carrying value.

In the first quarter of 2019, both CS and PS reporting units projected a decline in the estimated future cash flows primarily triggered by additional U.K. government actions which were announced on June 29, 2018. Accordingly, we performed an interim goodwill impairment test for these reporting units. As a result, we determined that the carrying values of these reporting units exceeded their estimated fair value and recorded non-cash goodwill impairment charges of $332 million (pre-tax and after-tax) primarily for our CS reporting unit. The discount rate and terminal growth rate used for the CS reporting unit in the first quarter 2019 impairment test were 8.5% and 1.25%. The discount rate and terminal growth rate used for the PS reporting unit in the first quarter 2019 impairment test were 8.0% and 1.25%.

In the fourth quarter of 2019, as a result of our annual goodwill impairment test, we determined that the carrying values of our CS and PS reporting units exceeded their estimated fair value and recorded non-cash charges of $465 million ($445 million after-tax) for the CS reporting unit and $741 million (pre-tax and after-tax) for the PS reporting unit. The additional impairments were primarily due to declines in the reporting units’ estimated future cash flows and the selection of higher discount rates. The declines in estimated future cash flows were primarily attributed to additional government reimbursement reductions and competitive pressures within the U.K. The risk of successfully achieving certain business initiatives was the primary factor in the use of a higher discount rate. The discount rate and terminal growth rate used for the CS reporting unit in our 2019 annual impairment test were 10.0% and 1.25%. The discount rate and terminal growth rate used for the PS reporting unit in our 2019 annual impairment test were 9.0% and 1.25%. At March 31, 2019, both CS and PS reporting units had no remaining goodwill balances.

Fiscal 2018

In 2018, we recorded total non-cash charges of $1,283 million (pre-tax and after-tax) to impair the carrying value of goodwill within our European Pharmaceutical Solutions segment.

During the second quarter of 2018, our former McKesson Europe reporting unit projected a decline in its estimated future cash flows primarily triggered by government reimbursement reductions in their retail business in the U.K. Accordingly, we performed an interim one-step goodwill impairment test in accordance with the amended goodwill guidance for this reporting unit prior to our annual impairment test. As a result of the interim impairment test, we determined that the carrying value of this reporting unit exceeded its estimated fair value and recorded a non-cash charge of $350 million (pre-tax and after-tax) to impair the carrying value of this reporting unit’s goodwill. The discount rate and terminal growth rate used in our 2018 second quarter impairment test were 7.5% and 1.25% compared to 7.0% and 1.5% in our 2017 annual impairment test.

Additionally, as a result of our 2018 annual impairment test, we determined that the carrying value of the former McKesson Europe reporting unit further exceeded its estimated fair value and recorded a non-cash goodwill impairment charge of $933 million (pre-tax and after-tax) in the fourth quarter of 2018. This reporting unit had a further decline in its estimated future cash flows driven by weakening script growth outlook in our U.K. business and by a more competitive environment in France during the fourth quarter of 2018. The discount rate and terminal growth rate used in our 2018 annual impairment test were 8.0% and 1.25%.

Rexall Health:

Fiscal 2018

In 2018, as a result of our 2018 annual impairment test, we determined that the carrying value of our Rexall Health reporting unit within Other exceeded its estimated fair value and recorded a non-cash goodwill impairment charge of $455 million (pre-tax and after-tax). The impairment was the result of a decline in estimated future cash flows primarily driven by significant generics reimbursement reductions across Canada and minimum wage increases in multiple provinces which can only be partially mitigated through the business’ cost saving efforts. The discount rate and terminal growth rate used in our impairment testing for this reporting unit were 10.0% and 2.0%. At March 31, 2019 and 2018, the Rexall Health reporting unit had no remaining goodwill related to our acquisition of Rexall Health.

Enterprise Information Solutions:

Fiscal 2017

In conjunction with the 2017 Healthcare Technology Net Asset Exchange, we evaluated strategic options for our EIS business, which was a reporting unit within Other. In 2017, we recorded a non-cash pre-tax charge of $290 million ($282 million after-tax) to impair the carrying value of this reporting unit’s goodwill. The impairment primarily resulted from a decline in estimated cash flows. The amount of goodwill impairment for the EIS reporting unit was determined under the former accounting guidance on goodwill impairment testing, and computed as the excess of the carrying value of the reporting unit’s goodwill over its implied fair value of its goodwill.

Refer to Financial Note 21, “Fair Value Measurements,” for more information on this nonrecurring fair value measurement.