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FAIR VALUE MEASUREMENTS - Narrative (Details) $ in Millions | 9 Months Ended |  |  |
--- | --- | --- | --- | ---
Sep. 30, 2021 USD ($) | Mar. 31, 2021 USD ($) | Dec. 31, 2020 USD ($) | Mar. 31, 2020 USD ($)
Recurring Basis |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |
Assets at fair value | $ 14,859 |  | $ 14,054 |
Level 3 | Recurring Basis |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |
Assets at fair value | 330 |  | 200 |
Long-term Investments | Investment in private company equity securities |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |
Investment in equity securities without readily determinable FV | $ 69 |  | 455 |
Grab | Redeemable Convertible Preferred Stock | Relative Weighting | Market Approach |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |
Fair value measurement inputs | 0.70 |  |  |
Grab | Redeemable Convertible Preferred Stock | Relative Weighting | Income Approach |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |
Fair value measurement inputs | 0.30 |  |  |
Grab | Redeemable Convertible Preferred Stock | Volatility | Market Approach |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |
Fair value measurement inputs | 0.65 |  |  |
Grab | Redeemable Convertible Preferred Stock | Expected Term | Market Approach |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |
Time to liquidity | 3 months |  |  |
Grab | Redeemable Convertible Preferred Stock | Expected Term | Income Approach |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |
Time to liquidity | 5 months |  |  |
Grab | Redeemable Convertible Preferred Stock | Minimum | Volatility | Income Approach |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |
Fair value measurement inputs | 0.60 |  |  |
Grab | Redeemable Convertible Preferred Stock | Minimum | Weighted average cost of capital | Income Approach |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |
Fair value measurement inputs | 0.120 |  |  |
Grab | Redeemable Convertible Preferred Stock | Minimum | EBITDA Multiple | Income Approach |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |
Fair value measurement inputs | 12 |  |  |
Grab | Redeemable Convertible Preferred Stock | Maximum | Volatility | Income Approach |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |
Fair value measurement inputs | 0.70 |  |  |
Grab | Redeemable Convertible Preferred Stock | Maximum | Weighted average cost of capital | Income Approach |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |
Fair value measurement inputs | 0.145 |  |  |
Grab | Redeemable Convertible Preferred Stock | Maximum | EBITDA Multiple | Income Approach |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |
Fair value measurement inputs | 14 |  |  |
Grab | Long-term Investments | Redeemable Convertible Preferred Stock |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |
Amortized cost of available-for-sale debt securities | $ 200 |  | 200 |
Grab | Long-term Investments | Redeemable Convertible Preferred Stock | Level 3 | Recurring Basis |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |
Assets at fair value | 330 |  | 200 |
DiDi Global Inc. | Long-term Investments | Investment in private company equity securities |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |
Investment in equity securities without readily determinable FV |  | $ 400 | $ 400 | $ 400
Trip.com Group, Convertible Senior Notes, Issued September 2016 | Short-term Investments | Convertible Debt Securities |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |
Amortized cost of available-for-sale debt securities | $ 25 |  |  |

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