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

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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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Hedging Activities - Narrative (Details) € in Millions, $ in Millions	12 Months Ended
	Mar. 31, 2019 USD ($)	Mar. 31, 2018 USD ($)	Mar. 31, 2017 USD ($)	Mar. 31, 2019 CAD ($)	Mar. 31, 2019 EUR (€)	Nov. 30, 2018 CAD ($)	Nov. 30, 2018 GBP (£)	Mar. 31, 2018 GBP (£)
Derivative [Line Items]
Total debt outstanding	$ 7,595	$ 7,880
Gains (losses) from net investment hedges	259	(268)	$ (13)
Gains (losses) recorded in other comprehensive income	24	(30)	(19)
Derivatives Designated for Hedge Accounting
Derivative [Line Items]
Gains (losses) recorded in other comprehensive income	28	(30)	$ (19)
Forward Contracts \| Derivatives Designated for Hedge Accounting
Derivative [Line Items]
Derivative, notional amount	81	162
Foreign Exchange Contract \| Derivatives Not Designated for Hedge Accounting \| United Kingdom, Pounds
Derivative [Line Items]
Derivative, notional amount	28	29
Currency Swap \| Derivatives Designated for Hedge Accounting
Derivative [Line Items]
Derivative, notional amount	2,908	3,412
Net Investment Hedging
Derivative [Line Items]
Gains (losses) recorded in other comprehensive income	$ 53	$ (7)
Net Investment Hedging \| Cross Currency Swap
Derivative [Line Items]
Derivative, notional amount				$ 499,000,000				£ 432,000,000
Net Investment Hedging \| November 2018 Cross Currency Swaps \| Derivatives Designated for Hedge Accounting
Derivative [Line Items]
Derivative, notional amount						$ 1,000,000,000	£ 500,000,000
Euro Denominated Notes \| Notes
Derivative [Line Items]
Total debt outstanding \| €					€ 1,950
British Pound Sterling Denominated Notes \| Notes
Derivative [Line Items]
Total debt outstanding \| £								£ 450,000,000