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Hedging Activities - Derivative Instruments Fair Value (Details) - USD ($) $ in Millions | Sep. 30, 2018 | Mar. 31, 2018
--- | --- | ---
Derivatives designated for hedge accounting |  |
Derivatives, Fair Value [Line Items] |  |
Fair value of derivative, asset | $ 105 | $ 29
Fair value of derivative, liability | 127 | 229
Derivatives designated for hedge accounting | Foreign Exchange Contract | Prepaid expenses and other |  |
Derivatives, Fair Value [Line Items] |  |
Fair value of derivative, asset | 15 | 15
Fair value of derivative, liability | 0 | 0
U.S. Dollar notional amount, asset | 81 | 81
Derivatives designated for hedge accounting | Foreign Exchange Contract | Other noncurrent assets |  |
Derivatives, Fair Value [Line Items] |  |
Fair value of derivative, asset | 15 | 14
Fair value of derivative, liability | 0 | 0
U.S. Dollar notional amount, asset | 81 | 81
Derivatives designated for hedge accounting | Cross Currency Swap | Prepaid expenses and other |  |
Derivatives, Fair Value [Line Items] |  |
Fair value of derivative, asset | 31 | 0
Derivatives designated for hedge accounting | Cross Currency Swap | Other noncurrent assets |  |
Derivatives, Fair Value [Line Items] |  |
Fair value of derivative, asset | 44 | 0
Derivatives designated for hedge accounting | Cross Currency Swap | Prepaid expenses and other/Other accrued liabilities |  |
Derivatives, Fair Value [Line Items] |  |
U.S. Dollar notional amount, asset | 371 | 504
Derivatives designated for hedge accounting | Cross Currency Swap | Other accrued liabilities |  |
Derivatives, Fair Value [Line Items] |  |
Fair value of derivative, liability | 12 | 7
Derivatives designated for hedge accounting | Cross Currency Swap | Other noncurrent liabilities |  |
Derivatives, Fair Value [Line Items] |  |
Fair value of derivative, liability | 115 | 222
Derivatives designated for hedge accounting | Cross Currency Swap | Non-current Asset / Liability |  |
Derivatives, Fair Value [Line Items] |  |
U.S. Dollar notional amount, asset | 3,508 | 3,508
Derivatives not designated for hedge accounting |  |
Derivatives, Fair Value [Line Items] |  |
Fair value of derivative, asset | 0 | 0
Fair value of derivative, liability | 0 | 0
Derivatives not designated for hedge accounting | Foreign Exchange Contract | Prepaid expenses and other |  |
Derivatives, Fair Value [Line Items] |  |
Fair value of derivative, asset | 0 | 0
Fair value of derivative, liability | 0 | 0
U.S. Dollar notional amount, asset | 25 | 13
Derivatives not designated for hedge accounting | Foreign Exchange Contract | Other accrued liabilities |  |
Derivatives, Fair Value [Line Items] |  |
Fair value of derivative, asset | 0 | 0
Fair value of derivative, liability | 0 | 0
U.S. Dollar, notional amount, liability | $ 15 | $ 16

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- Definition Fair value, before effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes assets elected not to be offset. Excludes assets not subject to a master netting arrangement. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 20 -Section 50 -Paragraph 3 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=51824906&loc=SL20225862-175312 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4B -Subparagraph (a),(c) -URI http://asc.fasb.org/extlink&oid=84234895&loc=SL5624163-113959 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 20 -Section 55 -Paragraph 7 -URI http://asc.fasb.org/extlink&oid=82849420&loc=SL20226000-175313 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 860 -SubTopic 20 -Section 50 -Paragraph 4D -Subparagraph (c)(2) -URI http://asc.fasb.org/extlink&oid=82924980&loc=SL51823488-111719 + Details
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