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Fair Value Measurements (Narrative) (Details) - USD ($) $ in Millions | 9 Months Ended |
--- | --- | ---
Sep. 30, 2024 | Sep. 30, 2023 | Dec. 31, 2023
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |
Carrying value of investment | $ 275 |  | $ 266
Equity securities | 19 |  | 16
Equity investments without readily determinable market value | 21 |  | 20
Private Insurance and Consulting |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |
Carrying value of investment | 74 |  | 63
Private Equity Investments |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |
Carrying value of investment | 201 |  | 203
Commitments for potential future investments | 120 |  |
Fair Value, Measurements, Recurring |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |
Equity securities | 8 |  | 5
Unobservable Inputs (Level 3) | Fair Value, Measurements, Recurring |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |
Proceeds from contingent purchase consideration, asset | 1 |  |
Equity securities | $ 0 |  | $ 0
Minimum |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |
Revenue target period (in years) | 2 years | 2 years |
Maximum |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |
Revenue target period (in years) | 4 years | 4 years |

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