Goodwill and Intangible Assets, Net - Narrative - Intangible Assets (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Goodwill [Line Items]
Goodwill impairment charge	$ 0	$ 69	$ 0	$ 69
Amortization expense of intangible assets	84	106	182	212
Finite-Lived Intangible Assets, Amortization Expense, Maturity Schedule [Abstract]
Estimated annual amortization expense, remainder of 2022	167		167
Estimated annual amortization expense, 2023	242		242
Estimated annual amortization expense, 2024	230		230
Estimated annual amortization expense, 2025	225		225
Estimated annual amortization expense, 2026	192		192
Estimated annual amortization expense, thereafter	$ 1,300		$ 1,300
International \| Retail Pharmacy Reporting Unit
Goodwill [Line Items]
Goodwill impairment charge		$ 69		$ 69

Finite-Lived Intangible Asset, Expected Amortization, after Year Four

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The aggregate expense charged against earnings to allocate the cost of intangible assets (nonphysical assets not used in production) in a systematic and rational manner to the periods expected to benefit from such assets. As a noncash expense, this element is added back to net income when calculating cash provided by or used in operations using the indirect method.

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Amount of amortization for assets, excluding financial assets and goodwill, lacking physical substance with finite life expected to be recognized in next fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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Amount of amortization for assets, excluding financial assets and goodwill, lacking physical substance with finite life expected to be recognized in remainder of current fiscal year.

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Amount of amortization for assets, excluding financial assets and goodwill, lacking physical substance with finite life expected to be recognized in fourth fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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Amount of amortization for assets, excluding financial assets and goodwill, lacking physical substance with finite life expected to be recognized in third fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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Amount of amortization for assets, excluding financial assets and goodwill, lacking physical substance with finite life expected to be recognized in second fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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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.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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