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Income Taxes - Narrative (Details) - USD ($) $ in Millions |  | 3 Months Ended | 12 Months Ended |
--- | --- | --- | --- | ---
Mar. 09, 2020 | Mar. 31, 2020 | Mar. 31, 2022 | Mar. 31, 2021 | Mar. 31, 2020 | Mar. 31, 2019
Income Tax Contingency [Line Items] |  |  |  |  |  |
Income tax expense (benefit) rates (percent) |  |  | 33.00% | (13.80%) | 1.60% |
Statutory federal income tax rate (percent) |  |  | 21.00% | 21.00% | 21.00% |
European businesses held for sale |  |  | $ 1,509 | $ 0 | $ 0 |
Deferred tax benefit |  |  | (34) | 908 | 342 |
Net discrete tax benefit |  |  |  | 105 |  |
Valuation allowance |  |  | 726 | 864 |  |
Increase (decrease) in valuation allowance |  |  | 138 |  |  |
Unrecognized tax benefits |  | $ 958 | 1,523 | 1,754 | 958 | $ 1,052
Unrecognized tax benefits that would Impact income tax expense and the effective tax rate |  |  | 1,300 |  |  |
Unrecognized tax benefits, reduction resulting from lapse of applicable statute of limitations |  |  | 102 | 12 | 13 |
Amount of decrease in unrecognized tax benefits that is reasonably possible in the next twelve months |  |  | 170 |  |  |
Income tax expense (benefit), before any tax effect, related to accrued interest and penalties |  |  | 8 | 9 | 23 |
Undistributed earnings of foreign operations |  |  | 5,000 |  |  |
Accrued interest and penalties on unrecognized tax benefits |  |  | 108 | 101 |  |
U.K. Businesses (Disposal Group) and Austrian Business |  |  |  |  |  |
Income Tax Contingency [Line Items] |  |  |  |  |  |
European businesses held for sale |  |  | 1,200 |  |  |
Held-for-sale | E.U. Businesses (Disposal Group) |  |  |  |  |  |
Income Tax Contingency [Line Items] |  |  |  |  |  |
European businesses held for sale |  |  | 438 |  |  |
Unrecognized tax benefits, reduction resulting from lapse of applicable statute of limitations |  |  | 23 |  |  |
Change Healthcare |  |  |  |  |  |
Income Tax Contingency [Line Items] |  |  |  |  |  |
Gain from sale of equity method investment | $ 414 | 414 |  |  |  |
Change Healthcare | Corporate Joint Venture |  |  |  |  |  |
Income Tax Contingency [Line Items] |  |  |  |  |  |
Gain from sale of equity method investment |  | $ 414 |  |  | (414) |
Federal |  |  |  |  |  |
Income Tax Contingency [Line Items] |  |  |  |  |  |
Federal, state and foreign net operating loss carryforwards |  |  | 303 |  |  |
State |  |  |  |  |  |
Income Tax Contingency [Line Items] |  |  |  |  |  |
Federal, state and foreign net operating loss carryforwards |  |  | 3,900 |  |  |
Foreign Tax Authority |  |  |  |  |  |
Income Tax Contingency [Line Items] |  |  |  |  |  |
Federal, state and foreign net operating loss carryforwards |  |  | 1,500 |  |  |
International |  |  |  |  |  |
Income Tax Contingency [Line Items] |  |  |  |  |  |
European businesses held for sale |  |  |  | 58 | $ 275 |
National Prescription Opiate Litigation |  |  |  |  |  |
Income Tax Contingency [Line Items] |  |  |  |  |  |
Loss contingency accrual, period increase (decrease) |  |  | 274 | 8,100 |  |
Loss contingency accrual, period increase (decrease), net of tax |  |  | 237 | $ 6,800 |  |
Capital Loss Carryforward | Foreign Tax Authority |  |  |  |  |  |
Income Tax Contingency [Line Items] |  |  |  |  |  |
Federal, state and foreign net operating loss carryforwards |  |  | $ 785 |  |  |

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