Aggregate notional amount specified by the derivative(s). Expressed as an absolute value.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
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Amount of increase (decrease) in the fair value of derivatives recognized in the income statement.

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Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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Amount after tax and reclassification adjustments, of increase (decrease) in accumulated gain (loss) from derivative instruments designated and qualifying as the effective portion of cash flow hedges and an entity's share of an equity investee's increase (decrease) in deferred hedging gain (loss).

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Amount, before tax, of increase (decrease) in the cumulative translation adjustment from gain (loss) on foreign currency derivatives that are designated as, and are effective as, economic hedges of a net investment in a foreign entity.

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Current period adjustment in other comprehensive income reflecting gains or losses on foreign currency transactions that are designated as, and are effective as, hedges of a net investment in a foreign entity, net of tax effect.

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Hedging Activities - Narrative (Details) € in Millions, £ in Millions	12 Months Ended
	Mar. 31, 2018 USD ($)	Mar. 31, 2017 USD ($)	Mar. 31, 2016 USD ($)	Mar. 31, 2018 EUR (€)	Mar. 31, 2018 USD ($)	Mar. 31, 2018 GBP (£)
Derivative [Line Items]
Total debt outstanding		$ 8,362,000,000			$ 7,880,000,000
Losses from net investment hedges	$ 268,000,000	13,000,000
(Losses) gains recorded in other comprehensive income	(30,000,000)	(19,000,000)	$ 9,000,000
Derivatives Designated for Hedge Accounting
Derivative [Line Items]
(Losses) gains recorded in other comprehensive income	(30,000,000)	(19,000,000)	9,000,000
Forward Contracts \| Derivatives Designated for Hedge Accounting
Derivative [Line Items]
Derivative, notional amount		243,000,000			162,000,000
Foreign Exchange Contract \| Derivatives Not Designated for Hedge Accounting
Derivative [Line Items]
Net gains on derivatives	0	5,000,000	$ 60,000,000
Currency Swap \| Derivatives Designated for Hedge Accounting
Derivative [Line Items]
Derivative, notional amount		2,663,000,000			3,412,000,000
Euro Denominated Notes \| Notes
Derivative [Line Items]
Total debt outstanding \| €				€ 1,950
British Pound Sterling Denominated Notes \| Notes
Derivative [Line Items]
Total debt outstanding \| £						£ 450
Canada, Dollars \| Foreign Exchange Contract \| Derivatives Not Designated for Hedge Accounting
Derivative [Line Items]
Derivative, notional amount		173,000,000
United Kingdom, Pounds \| Foreign Exchange Contract \| Derivatives Not Designated for Hedge Accounting
Derivative [Line Items]
Derivative, notional amount		$ 62,000,000			$ 29,000,000
Net Investment Hedging
Derivative [Line Items]
Losses recorded in other comprehensive income	$ 7,000,000
Net Investment Hedging \| Cross Currency Swap
Derivative [Line Items]
Derivative, notional amount \| £						£ 432