Income Taxes - Gross Unrecognized Tax Benefits (Details) - USD ($) $ in Millions	12 Months Ended
Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2018
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Unrecognized tax benefits at beginning of period	$ 1,052	$ 1,183	$ 486
Additions based on tax positions related to prior years	20	78	47
Reductions based on tax positions related to prior years	(168)	(234)	(124)
Additions based on tax positions related to current year	82	68	778
Reductions based on settlements	(8)	(13)	(7)
Reductions based on the lapse of the applicable statutes of limitations	(13)	(25)	0
Exchange rate fluctuations	(7)	(5)	3
Unrecognized tax benefits at end of period	$ 958	$ 1,052	$ 1,183

Unrecognized Tax Benefits, Increase (Decrease) Resulting from Foreign Currency Translation

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- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

+ References

No definition available.

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- Definition

Amount of unrecognized tax benefits.

+ References

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Amount of decrease in unrecognized tax benefits resulting from tax positions taken in prior period tax returns.

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Amount of decrease in unrecognized tax benefits resulting from settlements with taxing authorities.

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Amount of increase in unrecognized tax benefits resulting from tax positions that have been or will be taken in current period tax return.

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Amount of increase in unrecognized tax benefits resulting from tax positions taken in prior period tax returns.

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Amount of decrease in unrecognized tax benefits resulting from lapses of applicable statutes of limitations.

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