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Hedging Activities - Narrative (Details) £ in Millions | 3 Months Ended | 9 Months Ended |  |  |  |  |  |  |
--- | --- | --- | --- | --- | --- | --- | --- | --- | ---
Dec. 31, 2020 USD ($) | Dec. 31, 2019 USD ($) | Dec. 31, 2020 USD ($) | Dec. 31, 2019 USD ($) | Dec. 31, 2020 EUR (€) | Dec. 31, 2020 CAD ($) | Dec. 31, 2020 GBP (£) | Nov. 30, 2020 CAD ($) | Apr. 27, 2020 USD ($) | Apr. 27, 2020 EUR (€) | Mar. 31, 2020 USD ($) | Mar. 31, 2020 EUR (€) | Mar. 31, 2020 CAD ($) | Dec. 31, 2019 EUR (€) | Dec. 31, 2019 GBP (£) | Sep. 30, 2019 GBP (£) | Jun. 30, 2019 GBP (£)
Derivative [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Gains (losses) on non-derivative net investment hedge |  | $ (3,000,000) |  | $ 26,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |
Gains (losses) from cash flow hedges recorded within other comprehensive income | $ (12,000,000) | 8,000,000 | $ (36,000,000) | 33,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |
Derivatives designated for hedge accounting |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Gain (loss) from net investment hedges recorded within other comprehensive income | (84,000,000) | (59,000,000) | (201,000,000) | 8,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |
Forward contracts to hedge Euro against British Pound cash flows | Derivatives not Designated for Hedge Accounting |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Notional values of financial instruments | 13,000,000 | 250,000,000 | 13,000,000 | 250,000,000 |  |  |  |  |  |  | $ 29,000,000 |  |  |  |  |  |
Gain (loss) on financial instruments |  | 3,000,000 |  | (36,000,000) |  |  |  |  |  |  |  |  |  |  |  |  |
Net Investment Hedging | Derivatives designated for hedge accounting |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Derivatives used in net investment hedge, gains (losses) gross | (45,000,000) | (20,000,000) | (108,000,000) | (11,000,000) |  |  |  |  |  |  |  |  |  |  |  |  |
Net Investment Hedging | November 2018 cross currency swaps | Derivatives designated for hedge accounting |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Notional values of financial instruments |  |  |  |  |  | $ 999,000,000 |  | $ 500,000,000 |  |  |  |  | $ 1,500,000,000 |  |  |  | £ 932
Proceeds from termination of derivative instruments |  |  |  | 84,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |
Gain (loss) on financial instruments |  |  |  | 34,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |
Cash Flow Hedging | Derivatives designated for hedge accounting |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Gains (losses) from cash flow hedges recorded within other comprehensive income | (14,000,000) | $ 5,000,000 | (42,000,000) | $ 40,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |
Cash Flow Hedging | Cross currency swap | Derivatives designated for hedge accounting |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Notional values of financial instruments | $ 2,600,000,000 |  | $ 2,600,000,000 |  |  |  |  |  |  |  | $ 2,900,000,000 |  |  |  |  |  |
Cash Flow Hedging | Forward starting interest rate swaps | Derivatives designated for hedge accounting |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Notional values of financial instruments |  |  |  |  |  |  |  |  | $ 500,000,000 | € 600,000,000 |  |  |  |  |  |  |
Euro Denominated Notes | Term Loan |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Long-term debt outstanding | € |  |  |  |  |  |  |  |  |  |  |  |  |  | € 1,700,000,000 |  |  |
Euro Denominated Notes | Term Loan | Derivatives not Designated for Hedge Accounting |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Long-term debt outstanding | € |  |  |  |  |  |  |  |  |  |  |  |  |  | € 250,000,000 |  |  |
Euro Denominated Notes | Term Loan | Net Investment Hedging |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Long-term debt outstanding | € |  |  |  |  | € 1,700,000,000 |  |  |  |  |  |  | € 1,700,000,000 |  |  |  |  |
British Pound Sterling Denominated Notes | Term Loan |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Long-term debt outstanding | £ |  |  |  |  |  |  | £ 450 |  |  |  |  |  |  |  | £ 450 | £ 450 |
2025 Notes | Term Loan |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt instrument term |  |  | 5 years |  |  |  |  |  |  |  |  |  |  |  |  |  |

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