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Hedging Activities - Narrative (Details) € in Millions, £ in Millions, $ in Millions | 1 Months Ended | 3 Months Ended | 12 Months Ended |  |  |  |  |  |
--- | --- | --- | --- | --- | --- | --- | --- | --- | ---
Jan. 31, 2026 USD ($) | Jun. 30, 2025 USD ($) | Mar. 31, 2026 USD ($) | Mar. 31, 2025 USD ($) | Mar. 31, 2024 USD ($) | Mar. 31, 2026 CAD ($) | Mar. 31, 2026 GBP (£) | Mar. 31, 2026 EUR (€) | Mar. 31, 2026 USD ($) | Dec. 31, 2025 EUR (€) | Nov. 30, 2025 EUR (€) | Sep. 30, 2025 EUR (€) | Mar. 31, 2025 CAD ($) | Mar. 31, 2025 GBP (£) | Mar. 31, 2025 EUR (€) | Mar. 31, 2025 USD ($) | Mar. 31, 2024 GBP (£)
Derivative [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Other comprehensive income (loss), cash flow hedge, gain (loss), reclassification before tax |  |  |  | $ 0 | $ 0 |  |  |  |  |  |  |  |  |  |  |  |
1.50% Euro Notes due November 17, 2025 | Loans payable |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Interest rate on debt instruments (as percent) |  |  |  |  |  | 1.50% | 1.50% | 1.50% | 1.50% | 1.50% |  |  |  |  |  |  |
Cross-currency swaps | Cash Flow Hedging | Derivatives designated for hedge accounting: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Other comprehensive income (loss), cash flow hedge, gain (loss), reclassification before tax |  |  | $ 0 |  |  |  |  |  |  |  |  |  |  |  |  |  |
Interest rate swaps (non-current) | Fair Value Hedges | Derivatives designated for hedge accounting: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Notional |  |  |  |  |  |  |  |  | $ 1,300,000,000 |  |  |  |  |  |  |  |
Derivative, notional mount, terminated |  |  |  |  |  |  |  |  | 500,000,000 |  |  |  |  |  |  |  |
Interest rate swaps (non-current) | Cash Flow Hedging | Derivatives designated for hedge accounting: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Notional |  | $ 1,400,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Derivative, notional amount, entered into during period |  | $ 550,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Foreign currency forwards | Cash Flow Hedging | Derivatives designated for hedge accounting: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Other comprehensive income (loss), cash flow hedge, gain (loss), reclassification before tax |  |  | $ 12,000,000 |  | $ 0 |  |  |  |  |  |  |  |  |  |  |  |
CAD | Cross-currency swaps | Net Investment Hedging | Derivatives designated for hedge accounting: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Notional |  |  |  |  |  | $ 6,500 |  |  |  |  |  |  | $ 6,500 |  |  |  |
EUR | Cross-currency swaps | Fair Value Hedges | Derivatives designated for hedge accounting: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Notional | € |  |  |  |  |  |  |  | € 500 |  |  |  |  |  |  | € 1,100 |  |
Derivative instruments in hedges, settled at fair value net | € |  |  |  |  |  |  |  |  |  | € 600 |  | € 600 |  |  |  |  |
Derivative instruments in hedges, acquired at fair value | € |  |  |  |  |  |  |  |  |  |  | € 600 |  |  |  |  |  |
USD | Interest rate swaps (non-current) | Fair Value Hedges | Derivatives designated for hedge accounting: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Notional |  |  |  |  |  |  |  |  | 750,000,000 |  |  |  |  |  |  | $ 750,000,000 |
USD | Interest rate swaps (non-current) | Cash Flow Hedging | Derivatives designated for hedge accounting: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Notional |  |  |  |  |  |  |  |  | $ 0 |  |  |  |  |  |  | $ 850,000,000 |
USD | Foreign currency forwards | Cash Flow Hedging | Derivatives designated for hedge accounting: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Notional | $ 791,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Other comprehensive income (loss), cash flow hedge, gain (loss), reclassification before tax | $ 30,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
GBP | Cross-currency swaps | Fair Value Hedges | Derivatives designated for hedge accounting: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Notional | £ |  |  |  |  |  |  | £ 450 |  |  |  |  |  |  | £ 450 |  |  |
GBP | Foreign currency forwards | Cash Flow Hedging | Derivatives designated for hedge accounting: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Notional | £ |  |  |  |  |  |  | £ 0 |  |  |  |  |  |  | £ 11 |  |  | £ 45

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