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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 | Dec. 31, 2022 | Dec. 31, 2021
--- | --- | ---
Financial instruments owned: |  |
Total assets measured at fair value | $ 330 | $ 691
Fiduciary Assets: |  |
Total fiduciary assets measured at fair value | 201 | 582
Liabilities: |  |
Total liabilities measured at fair value | 377 | 352
Identical Assets (Level 1) |  |
Financial instruments owned: |  |
Total assets measured at fair value | 314 | 678
Fiduciary Assets: |  |
Total fiduciary assets measured at fair value | 201 | 582
Liabilities: |  |
Total liabilities measured at fair value | 0 | 0
Observable Inputs (Level 2) |  |
Financial instruments owned: |  |
Total assets measured at fair value | 13 | 8
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 | 3 | 5
Fiduciary Assets: |  |
Total fiduciary assets measured at fair value | 0 | 0
Liabilities: |  |
Total liabilities measured at fair value | 377 | 352
US treasury bills |  |
Fiduciary Assets: |  |
Total fiduciary assets measured at fair value | 0 | 55
US treasury bills | Identical Assets (Level 1) |  |
Fiduciary Assets: |  |
Total fiduciary assets measured at fair value | 0 | 55
US treasury bills | Observable Inputs (Level 2) |  |
Fiduciary Assets: |  |
Total fiduciary assets measured at fair value | 0 | 0
US treasury bills | Unobservable Inputs (Level 3) |  |
Fiduciary Assets: |  |
Total fiduciary assets measured at fair value | 0 | 0
Money market funds |  |
Fiduciary Assets: |  |
Total fiduciary assets measured at fair value | 201 | 527
Money market funds | Identical Assets (Level 1) |  |
Fiduciary Assets: |  |
Total fiduciary assets measured at fair value | 201 | 527
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 | 6 | 61
Mutual funds | 162 | 192
Other equity investment | 13 | 8
Other Assets | Identical Assets (Level 1) |  |
Financial instruments owned: |  |
Exchange traded equity securities | 6 | 61
Mutual funds | 162 | 192
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 | 13 | 8
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 | 146 | 425
Cash and Cash Equivalents | Identical Assets (Level 1) |  |
Financial instruments owned: |  |
Money market funds | 146 | 425
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 asset | 3 | 5
Other Receivables | Identical Assets (Level 1) |  |
Financial instruments owned: |  |
Contingent purchase consideration asset | 0 | 0
Other Receivables | Observable Inputs (Level 2) |  |
Financial instruments owned: |  |
Contingent purchase consideration asset | 0 | 0
Other Receivables | Unobservable Inputs (Level 3) |  |
Financial instruments owned: |  |
Contingent purchase consideration asset | 3 | 5
Accounts Payable and Accrued Liabilities and Other Liabilities |  |
Liabilities: |  |
Contingent purchase consideration liability | 377 | 352
Accounts Payable and Accrued Liabilities and Other Liabilities | Identical Assets (Level 1) |  |
Liabilities: |  |
Contingent purchase consideration liability | 0 | 0
Accounts Payable and Accrued Liabilities and Other Liabilities | Observable Inputs (Level 2) |  |
Liabilities: |  |
Contingent purchase consideration liability | 0 | 0
Accounts Payable and Accrued Liabilities and Other Liabilities | Unobservable Inputs (Level 3) |  |
Liabilities: |  |
Contingent purchase consideration liability | $ 377 | $ 352

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