Other Income (Details) - USD ($) $ in Millions	12 Months Ended
Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2018
Other Income and Expenses [Abstract]
Non-service cost components of net periodic pension income	$ (658)	$ (182)	$ (509)
Foreign currency (gain) loss	(25)	31	(71)
Other gain	(37)	(155)	(13)
Totals	$ (720)	$ (306)	$ (593)

Amount before tax of foreign currency transaction realized and unrealized gain (loss) recognized in the income statement.

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Amount of expense (reversal of expense) for net periodic benefit cost components, excluding service cost component, of defined benefit plan. Amount includes, but is not limited to, interest cost, expected (return) loss on plan asset, amortization of prior service cost (credit), amortization of (gain) loss, amortization of transition (asset) obligation, settlement (gain) loss, curtailment (gain) loss and certain termination benefits.

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The net amount of other operating income and expenses, the components of which are not separately disclosed on the income statement, from items that are associated with the entity's normal revenue producing operations.

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The net realized gains or losses on investments during the period, not including gains or losses on securities separately or otherwise categorized as trading, available-for-sale, or held-to-maturity.

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