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Fair Value Measurements (Assets And Liabilities Measured At Fair Value On A Recurring Basis) (Details) - Fair Value, Measurements, Recurring - USD ($) $ in Millions | Sep. 30, 2023 | Dec. 31, 2022
--- | --- | ---
Financial instruments owned: |  |
Total assets measured at fair value | $ 754 | $ 330
Fiduciary Assets: |  |
Total fiduciary assets measured at fair value | 77 | 201
Liabilities: |  |
Total liabilities measured at fair value | 231 | 377
Identical Assets (Level 1) |  |
Financial instruments owned: |  |
Total assets measured at fair value | 753 | 314
Fiduciary Assets: |  |
Total fiduciary assets measured at fair value | 77 | 201
Liabilities: |  |
Total liabilities measured at fair value | 0 | 0
Observable Inputs (Level 2) |  |
Financial instruments owned: |  |
Total assets measured at fair value | 0 | 13
Fiduciary Assets: |  |
Total fiduciary assets measured at fair value | 0 | 0
Liabilities: |  |
Total liabilities measured at fair value | 0 | 0
Unobservable Inputs (Level 3) |  |
Financial instruments owned: |  |
Total assets measured at fair value | 1 | 3
Fiduciary Assets: |  |
Total fiduciary assets measured at fair value | 0 | 0
Liabilities: |  |
Total liabilities measured at fair value | 231 | 377
Money market funds |  |
Fiduciary Assets: |  |
Total fiduciary assets measured at fair value | 77 | 201
Money market funds | Identical Assets (Level 1) |  |
Fiduciary Assets: |  |
Total fiduciary assets measured at fair value | 77 | 201
Money market funds | Observable Inputs (Level 2) |  |
Fiduciary Assets: |  |
Total fiduciary assets measured at fair value | 0 | 0
Money market funds | Unobservable Inputs (Level 3) |  |
Fiduciary Assets: |  |
Total fiduciary assets measured at fair value | 0 | 0
Other Assets |  |
Financial instruments owned: |  |
Exchange traded equity securities | 5 | 6
Mutual funds | 163 | 162
Other equity investment | 0 | 13
Other Assets | Identical Assets (Level 1) |  |
Financial instruments owned: |  |
Exchange traded equity securities | 5 | 6
Mutual funds | 163 | 162
Other equity investment | 0 | 0
Other Assets | Observable Inputs (Level 2) |  |
Financial instruments owned: |  |
Exchange traded equity securities | 0 | 0
Mutual funds | 0 | 0
Other equity investment | 0 | 13
Other Assets | Unobservable Inputs (Level 3) |  |
Financial instruments owned: |  |
Exchange traded equity securities | 0 | 0
Mutual funds | 0 | 0
Other equity investment | 0 | 0
Cash and Cash Equivalents |  |
Financial instruments owned: |  |
Money market funds | 585 | 146
Cash and Cash Equivalents | Identical Assets (Level 1) |  |
Financial instruments owned: |  |
Money market funds | 585 | 146
Cash and Cash Equivalents | Observable Inputs (Level 2) |  |
Financial instruments owned: |  |
Money market funds | 0 | 0
Cash and Cash Equivalents | Unobservable Inputs (Level 3) |  |
Financial instruments owned: |  |
Money market funds | 0 | 0
Other Receivables |  |
Financial instruments owned: |  |
Contingent purchase consideration assets | 1 | 3
Other Receivables | Identical Assets (Level 1) |  |
Financial instruments owned: |  |
Contingent purchase consideration assets | 0 | 0
Other Receivables | Observable Inputs (Level 2) |  |
Financial instruments owned: |  |
Contingent purchase consideration assets | 0 | 0
Other Receivables | Unobservable Inputs (Level 3) |  |
Financial instruments owned: |  |
Contingent purchase consideration assets | 1 | 3
Accounts Payable and Accrued Liabilities and Other Liabilities |  |
Liabilities: |  |
Contingent purchase consideration liabilities | 231 | 377
Accounts Payable and Accrued Liabilities and Other Liabilities | Identical Assets (Level 1) |  |
Liabilities: |  |
Contingent purchase consideration liabilities | 0 | 0
Accounts Payable and Accrued Liabilities and Other Liabilities | Observable Inputs (Level 2) |  |
Liabilities: |  |
Contingent purchase consideration liabilities | 0 | 0
Accounts Payable and Accrued Liabilities and Other Liabilities | Unobservable Inputs (Level 3) |  |
Liabilities: |  |
Contingent purchase consideration liabilities | $ 231 | $ 377

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