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Goodwill and Intangible Assets, Net - Goodwill Impairment Inputs (Details) - USD ($) $ in Millions | 3 Months Ended | 12 Months Ended
--- | --- | ---
Mar. 31, 2019 | Dec. 31, 2018 | Jun. 30, 2018 | Mar. 31, 2021 | Mar. 31, 2020 | Mar. 31, 2019
Goodwill [Line Items] |  |  |  |  |  |
Goodwill impairment charge |  |  |  | $ 69 | $ 2 | $ 1,797
International |  |  |  |  |  |
Goodwill [Line Items] |  |  |  |  |  |
Goodwill impairment charge |  |  |  | 69 | $ 2 | $ 1,776
International | Pharmaceutical Distribution |  |  |  |  |  |
Goodwill [Line Items] |  |  |  |  |  |
Goodwill impairment, discount rate (percent) |  |  | 8.00% |  |  |
Goodwill impairment, terminal growth rate (percent) |  |  | 1.25% |  |  |
Goodwill impairment charge |  |  | $ 238 |  |  |
International | Retail Pharmacy |  |  |  |  |  |
Goodwill [Line Items] |  |  |  |  |  |
Goodwill impairment, discount rate (percent) | 10.00% |  | 8.50% |  |  |
Goodwill impairment, terminal growth rate (percent) | 1.25% |  | 1.25% |  |  |
Goodwill impairment charge | $ 465 |  | $ 251 | $ 69 |  |
International | Pharmaceutical Distribution |  |  |  |  |  |
Goodwill [Line Items] |  |  |  |  |  |
Goodwill impairment, discount rate (percent) |  |  | 8.00% |  |  |
Goodwill impairment, terminal growth rate (percent) |  |  | 1.25% |  |  |
Goodwill impairment charge |  |  | $ 81 |  |  |
International | Pharmaceutical Distribution |  |  |  |  |  |
Goodwill [Line Items] |  |  |  |  |  |
Goodwill impairment, discount rate (percent) | 9.00% |  |  |  |  |
Goodwill impairment, terminal growth rate (percent) | 1.25% |  |  |  |  |
Goodwill impairment charge | $ 741 |  |  |  |  |
International | Rexall Health |  |  |  |  |  |
Goodwill [Line Items] |  |  |  |  |  |
Goodwill impairment charge |  | $ 21 |  |  |  |

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- Definition Amount of loss from the write-down of an asset representing the future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 20 -Section 50 -Paragraph 2 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=121556970&loc=d3e13854-109267 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=121586364&loc=d3e3602-108585 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (e) -URI http://asc.fasb.org/extlink&oid=121556970&loc=d3e13816-109267 Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 20 -Section 45 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=99380562&loc=d3e13777-109266 + Details
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