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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, 2021 | Dec. 31, 2020
--- | --- | ---
Financial instruments owned: |  |
Total assets measured at fair value | $ 691 | $ 908
Fiduciary Assets: |  |
Total fiduciary assets measured at fair value | 582 | 323
Liabilities: |  |
Total liabilities measured at fair value | 352 | 243
Identical Assets (Level 1) |  |
Financial instruments owned: |  |
Total assets measured at fair value | 678 | 832
Fiduciary Assets: |  |
Total fiduciary assets measured at fair value | 582 | 323
Liabilities: |  |
Total liabilities measured at fair value | 0 | 0
Observable Inputs (Level 2) |  |
Financial instruments owned: |  |
Total assets measured at fair value | 8 | 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 | 5 | 68
Fiduciary Assets: |  |
Total fiduciary assets measured at fair value | 0 | 0
Liabilities: |  |
Total liabilities measured at fair value | 352 | 243
Money market funds |  |
Fiduciary Assets: |  |
Total fiduciary assets measured at fair value | 527 | 173
Money market funds | Identical Assets (Level 1) |  |
Fiduciary Assets: |  |
Total fiduciary assets measured at fair value | 527 | 173
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
U.S. Treasury Bills(e) |  |
Fiduciary Assets: |  |
Total fiduciary assets measured at fair value | 55 | 150
U.S. Treasury Bills(e) | Identical Assets (Level 1) |  |
Fiduciary Assets: |  |
Total fiduciary assets measured at fair value | 55 | 150
U.S. Treasury Bills(e) | Observable Inputs (Level 2) |  |
Fiduciary Assets: |  |
Total fiduciary assets measured at fair value | 0 | 0
U.S. Treasury Bills(e) | Unobservable Inputs (Level 3) |  |
Fiduciary Assets: |  |
Total fiduciary assets measured at fair value | 0 | 0
Other Assets |  |
Financial instruments owned: |  |
Exchange traded equity securities | 61 | 59
Mutual funds | 192 | 186
Other equity investment | 8 | 8
Other Assets | Identical Assets (Level 1) |  |
Financial instruments owned: |  |
Exchange traded equity securities | 61 | 59
Mutual funds | 192 | 186
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 | 8 | 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 | 425 | 587
Cash and Cash Equivalents | Identical Assets (Level 1) |  |
Financial instruments owned: |  |
Money market funds | 425 | 587
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 | 5 | 68
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 | 5 | 68
Accounts Payable and Accrued Liabilities and Other Liabilities |  |
Liabilities: |  |
Contingent purchase consideration liability | 352 | 243
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 | $ 352 | $ 243

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