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Fair Value Measurements - Narrative (Details) - USD ($) $ in Millions | 3 Months Ended | 12 Months Ended
--- | --- | ---
Mar. 31, 2025 | Mar. 31, 2025 | Mar. 31, 2024 | Mar. 31, 2023
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |
Investments in equity and debt securities of growth stage companies | $ 103 | $ 103 | $ 240 |
Net gains (losses) on investments in equity securities |  | 101 | (24) | $ (36)
Gain related to share price increase of equity securities |  | 100 |  |
Proceeds from sale of equity securities |  | 92 |  |
Level 1 |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |
Gain related to share price increase of equity securities |  | 44 |  |
Proceeds from sale of equity securities | 97 |  |  |
Impairment loss | 44 |  |  |
Level 1 | Fair Value, Recurring |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |
Investments in money market funds | $ 1,000 | $ 1,000 | $ 705 |

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- Definition Investment in short-term money-market instruments (such as commercial paper, banker's acceptances, repurchase agreements, government securities, certificates of deposit, and so forth) which are highly liquid (that is, readily convertible to known amounts of cash) and so near their maturity that they present an insignificant risk of changes in value because of changes in interest rates. Generally, only investments with original maturities of three months or less qualify as cash equivalents by definition. Original maturity means an original maturity to the entity holding the investment. For example, both a three-month US Treasury bill and a three-year Treasury note purchased three months from maturity qualify as cash equivalents. However, a Treasury note purchased three-years ago does not become a cash equivalent when its remaining maturity is three months. + References No definition available. + Details
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