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Hedging Activities - Summary of Derivative Instruments Gain (Loss) (Details) - Derivatives designated for hedge accounting - USD ($) $ in Millions | 3 Months Ended | 6 Months Ended
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Sep. 30, 2023 | Sep. 30, 2022 | Sep. 30, 2023 | Sep. 30, 2022
Cross-currency swaps | Net Investment Hedging |  |  |  |
Derivatives, Fair Value [Line Items] |  |  |  |
Derivatives designated as net investment hedges: |  | $ 75 |  | $ 139
Derivatives designated as cash flow and other hedges: | $ 27 | 21 | $ 7 | 33
Cross-currency swaps | Cash Flow Hedges |  |  |  |
Derivatives, Fair Value [Line Items] |  |  |  |
Derivatives designated as cash flow and other hedges: | 33 | (3) | 27 | (5)
Fixed interest rate swaps | Cash Flow Hedges |  |  |  |
Derivatives, Fair Value [Line Items] |  |  |  |
Derivatives designated as cash flow and other hedges: | $ 0 | $ 28 | $ 16 | $ 55

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- Definition Amount, before tax, of reclassification of gain (loss) from accumulated other comprehensive income (AOCI) for derivative instrument designated and qualifying as cash flow hedge included in assessment of hedge effectiveness. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 220 -SubTopic 10 -Name Accounting Standards Codification -Section 45 -Paragraph 11 -Publisher FASB -URI https://asc.fasb.org//1943274/2147482790/220-10-45-11 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 220 -SubTopic 10 -Name Accounting Standards Codification -Section 45 -Paragraph 15 -Publisher FASB -URI https://asc.fasb.org//1943274/2147482790/220-10-45-15 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Name Accounting Standards Codification -Section 50 -Paragraph 4C -Subparagraph (c) -SubTopic 10 -Topic 815 -Publisher FASB -URI https://asc.fasb.org//1943274/2147480434/815-10-50-4C + Details
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