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Stockholders' Equity - Schedule of Other Comprehensive Income (Loss), Net of Tax (Details) - USD ($) $ in Millions	12 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2016
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss) before reclassifications	$ 604	$ (688)
Amounts reclassified to earnings	5	29
Other Comprehensive Income (Loss), Net of Tax	609	(659)	$ 172
Foreign Currency Translation Adjustments, Net of Tax
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss) before reclassifications	804	(644)	113
Amounts reclassified to earnings	0	20	0
Other Comprehensive Income (Loss), Net of Tax	804	(624)	113
Tax expense (benefit)	0	1	23
Reclassification, tax expense	0	0	0
Unrealized Losses on Net Investment Hedges, Net of Tax
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss) before reclassifications	(180)	(8)	0
Amounts reclassified to earnings	0	0	0
Other Comprehensive Income (Loss), Net of Tax	(180)	(8)	0
Tax expense (benefit)	95	5	0
Reclassification, tax expense	0	0	0
Unrealized Gains (Losses) on Cash Flow Hedges, Net of Tax
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss) before reclassifications	(30)	(19)	6
Amounts reclassified to earnings	0	0	3
Other Comprehensive Income (Loss), Net of Tax	(30)	(19)	9
Tax expense (benefit)	9	0	0
Reclassification, tax expense	0	0	0
Net actuarial gain (loss) and prior service credit (cost) arising during period, net of income tax expense (benefit) of $2, $4 and $13 (6)
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss) before reclassifications	25	(20)	23
Tax expense (benefit)	(2)	(4)	(13)
Reclassification, tax expense	2	4	18
Amortization of actuarial gain (loss), prior service cost and transition obligation, net of income tax expense (benefit) of $2, $4 and $18 (7)
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss) before reclassifications	5	9	30
Changes in Retirement-Related Benefit Plans, Foreign Currency Translation Adjustments and Other
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss) before reclassifications	(15)	3	(3)
Tax expense (benefit)	0	0	0
Reclassification, tax expense	0	0	0
Unrealized Net Gains (Losses) and Other Components of Benefit Plans, Net of Tax
Accumulated Other Comprehensive Income (Loss) [Line Items]
Amounts reclassified to earnings	0	0	0
Other Comprehensive Income (Loss), Net of Tax	$ 15	$ (8)	$ 50

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Amount after tax, before reclassification adjustments of other comprehensive income (loss).

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-Name Accounting Standards Codification
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-SubTopic 10
-Section 55
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Amount of tax expense (benefit) allocated to other comprehensive income (loss) before reclassification adjustment from accumulated other comprehensive income (loss).

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