Fair Value - Other Fair Value Disclosures (Details) $ in Millions	3 Months Ended	6 Months Ended
Sep. 30, 2017 USD ($) counterparty	Sep. 30, 2016 USD ($)	Sep. 30, 2017 USD ($) counterparty	Sep. 30, 2016 USD ($)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Goodwill impairment	$ 0	$ 0	$ 0	$ 0
Tangible asset impairment charges	0	0	0	0
Impairment of intangible assets	0	0	0	0
Impairment of other intangible assets	$ 0	$ 0	$ 0	$ 0
Number of counterparties with concentration of credit risk \| counterparty	8		8
Foreign currency forward contracts
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Maximum amount of loss the Company could incur			$ 30
Fair value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, net of current maturities	$ 6,000		6,000
Carrying value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, net of current maturities	$ 5,800		$ 5,800

Concentration Risk, Credit Risk, Number Of Counterparties

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Maximum amount of loss due to credit risk that, based on the gross fair value of the financial instrument, the entity would incur if parties to the financial instruments that make up the concentration failed completely to perform according to the terms of the contracts and the collateral or other security, if any, for the amount due proved to be of no value to the entity.

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Amount of loss from the write-down of an asset representing the future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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The amount of impairment loss recognized in the period resulting from the write-down of the carrying amount of an intangible asset (excluding goodwill) to fair value.

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The aggregate amount of write-downs for impairments recognized during the period for long lived assets held for use (including those held for disposal by means other than sale).

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Amount after unamortized (discount) premium and debt issuance costs of long-term debt classified as noncurrent and excluding amounts to be repaid within one year or the normal operating cycle, if longer. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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