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Hedging Activities - Narrative (Details) | 3 Months Ended | 9 Months Ended |  |  |  |
--- | --- | --- | --- | --- | --- | ---
Dec. 31, 2018 USD ($) | Dec. 31, 2017 USD ($) | Dec. 31, 2018 USD ($) | Dec. 31, 2017 USD ($) | Dec. 31, 2018 EUR (€) | Dec. 31, 2018 USD ($) | Dec. 31, 2018 GBP (£) | Nov. 30, 2018 CAD ($) | Nov. 30, 2018 GBP (£) | Mar. 31, 2018 USD ($) | Mar. 31, 2018 GBP (£) | Dec. 31, 2017 EUR (€)
Derivative [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Long-term debt outstanding |  |  |  |  |  | $ 8,736,000,000 |  |  |  | $ 7,880,000,000 |  |
Gains (losses) from net investment hedges recorded in other comprehensive income | $ 39,000,000 | $ (28,000,000) | $ 223,000,000 | $ (205,000,000) |  |  |  |  |  |  |  |
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), after Reclassification and Tax | 35,000,000 | (16,000,000) | 37,000,000 | (5,000,000) |  |  |  |  |  |  |  |
Derivatives Designated for Hedge Accounting |  |  |  |  |  |  |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), after Reclassification and Tax | 40,000,000 | $ 0 | 42,000,000 | $ 0 |  |  |  |  |  |  |  |
Foreign Exchange Contract | Derivatives not Designated for Hedge Accounting |  |  |  |  |  |  |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Notional values of financial instruments |  |  |  |  |  | 10,000,000 |  |  |  | 29,000,000 |  |
Cross Currency Swap | Derivatives Designated for Hedge Accounting |  |  |  |  |  |  |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Notional values of financial instruments |  |  |  |  |  | 3,279,000,000 |  |  |  | 3,412,000,000 |  |
Forward Contracts | Derivatives Designated for Hedge Accounting |  |  |  |  |  |  |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Notional values of financial instruments |  |  |  |  |  | $ 162,000,000 |  |  |  | $ 162,000,000 |  |
Net Investment Hedging | Derivatives Designated for Hedge Accounting |  |  |  |  |  |  |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Derivatives used in net investment hedge, gains (loss) gross | $ 63,000,000 |  | $ 102,000,000 |  |  |  |  |  |  |  |  |
Net Investment Hedging | November 2018 Cross Currency Swaps | Derivatives Designated for Hedge Accounting |  |  |  |  |  |  |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Notional values of financial instruments |  |  |  |  |  |  |  | $ 1,000,000,000 | £ 500,000,000 |  |  |
Net Investment Hedging | March 2018 Cross Currency Swaps | Derivatives Designated for Hedge Accounting |  |  |  |  |  |  |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Notional values of financial instruments | £ |  |  |  |  |  |  |  |  |  |  | £ 432,000,000 |
Euro Denominated Notes | Term Loan |  |  |  |  |  |  |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Long-term debt outstanding | € |  |  |  |  | € 1,950,000,000.00 |  |  |  |  |  |  | € 1,200,000,000.00
British Pound Sterling Denominated Notes | Term Loan |  |  |  |  |  |  |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Long-term debt outstanding | £ |  |  |  |  |  |  | £ 450,000,000 |  |  |  |  |
Minimum | Forward Contracts | Derivatives Designated for Hedge Accounting |  |  |  |  |  |  |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Contract maturity dates |  |  | Mar. 31, 2019 |  |  |  |  |  |  |  |  |
Maximum | Forward Contracts | Derivatives Designated for Hedge Accounting |  |  |  |  |  |  |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Contract maturity dates |  |  | Mar. 31, 2020 |  |  |  |  |  |  |  |  |

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