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Hedging Activities - Narrative (Details) £ in Millions | 12 Months Ended |  |  |  |  |  |  |
--- | --- | --- | --- | --- | --- | --- | --- | ---
Mar. 31, 2021 USD ($) | Mar. 31, 2020 USD ($) | Mar. 31, 2019 USD ($) | Mar. 31, 2021 EUR (€) | Mar. 31, 2021 CAD ($) | Dec. 31, 2020 EUR (€) | Apr. 27, 2020 USD ($) | Apr. 27, 2020 EUR (€) | Mar. 31, 2020 EUR (€) | Mar. 31, 2020 CAD ($) | Dec. 31, 2019 EUR (€) | Sep. 30, 2019 GBP (£) | Mar. 31, 2019 GBP (£)
Derivative [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Total debt outstanding | $ 7,148,000,000 | $ 7,387,000,000 |  |  |  |  |  |  |  |  |  |  |
Gains (losses) from net investment hedges | (118,000,000) | 39,000,000 | $ 259,000,000 |  |  |  |  |  |  |  |  |  |
Gains recorded in earnings for ineffectiveness of Company's non-derivative hedges |  | 34,000,000 |  |  |  |  |  |  |  |  |  |  |
Gains (losses) recorded in other comprehensive income | (36,000,000) | 86,000,000 | 24,000,000 |  |  |  |  |  |  |  |  |  |
Currency Swap | Derivatives Designated for Hedge Accounting |  |  |  |  |  |  |  |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Notional amounts of derivative | 2,600,000,000 | 2,900,000,000 |  |  |  |  |  |  |  |  |  |  |
Forward Contracts and Cross Currency Swaps |  |  |  |  |  |  |  |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Gains (losses) recorded in other comprehensive income | (42,000,000) | 98,000,000 | 28,000,000 |  |  |  |  |  |  |  |  |  |
Foreign Exchange Contract | Derivatives Not Designated for Hedge Accounting | United Kingdom, Pounds |  |  |  |  |  |  |  |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Notional amounts of derivative | 39,000,000 | 29,000,000 |  |  |  |  |  |  |  |  |  |  |
Forward Contracts to Offset Impact of Ineffectiveness of Net investment Hedges | Derivatives Not Designated for Hedge Accounting |  |  |  |  |  |  |  |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Notional amounts of derivative | € |  |  |  |  |  | € 250,000,000 |  |  |  |  |  |  |
Gains (losses) from contracts not designated as hedges |  | (44,000,000) |  |  |  |  |  |  |  |  |  |  |
Net Investment Hedging |  |  |  |  |  |  |  |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Gains (losses) recorded in other comprehensive income | $ (119,000,000) | 76,000,000 | $ 53,000,000 |  |  |  |  |  |  |  |  |  |
Net Investment Hedging | November 2018 Cross Currency Swaps | Derivatives Designated for Hedge Accounting |  |  |  |  |  |  |  |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Notional amounts of derivative |  |  |  |  | $ 500,000,000 |  |  |  |  | $ 1,500,000,000 |  |  | £ 932
Notional amount of derivatives that matured |  |  |  |  | $ 999,000,000 |  |  |  |  |  |  |  |
Proceeds from termination of swaps |  | 84,000,000 |  |  |  |  |  |  |  |  |  |  |
Settlement gain recorded in earnings |  | $ 34,000,000 |  |  |  |  |  |  |  |  |  |  |
Cash Flow Hedging | Interest Rate Swap | Derivatives Designated for Hedge Accounting |  |  |  |  |  |  |  |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Notional amounts of derivative |  |  |  |  |  |  | $ 500,000,000 | € 600,000,000 |  |  |  |  |
Euro Denominated Notes | Notes |  |  |  |  |  |  |  |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Total debt outstanding | € |  |  |  |  |  |  |  |  |  |  | € 250,000,000 |  |
Euro Denominated Notes | Notes | Net Investment Hedging |  |  |  |  |  |  |  |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Total debt outstanding | € |  |  |  | € 1,700,000,000 |  |  |  |  | € 1,700,000,000 |  |  |  |
British Pound Sterling Denominated Notes | Notes |  |  |  |  |  |  |  |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Total debt outstanding | £ |  |  |  |  |  |  |  |  |  |  |  | £ 450 | £ 450

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