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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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- Definition Amount after tax, before reclassification adjustments of other comprehensive income (loss). + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 55 -Paragraph 15 -URI http://asc.fasb.org/extlink&oid=84158357&loc=d3e1436-108581 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 14A -URI http://asc.fasb.org/extlink&oid=84228862&loc=SL7669686-108580 + Details
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- Definition Amount of tax expense (benefit) allocated to other comprehensive income (loss) before reclassification adjustment from accumulated other comprehensive income (loss). + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 20 -Section 45 -Paragraph 11 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=79507043&loc=d3e39076-109324 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 12 -URI http://asc.fasb.org/extlink&oid=84228862&loc=d3e640-108580 + Details
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