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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, 2018 | Dec. 31, 2017
--- | --- | ---
Financial instruments owned: |  |  |
Total assets measured at fair value |  | $ 311 | $ 382
Fiduciary Assets: |  |  |
Fiduciary assets |  | 69 | 111
Liabilities: |  |  |
Total liabilities measured at fair value |  | 268 | 189
Identical Assets (Level 1) |  |  |
Financial instruments owned: |  |  |
Total assets measured at fair value |  | 303 | 382
Fiduciary Assets: |  |  |
Fiduciary assets |  | 69 | 111
Liabilities: |  |  |
Total liabilities measured at fair value |  | 0 | 0
Observable Inputs (Level 2) |  |  |
Financial instruments owned: |  |  |
Total assets measured at fair value |  | 8 | 0
Fiduciary Assets: |  |  |
Fiduciary assets |  | 0 | 0
Liabilities: |  |  |
Total liabilities measured at fair value |  | 0 | 0
Unobservable Inputs (Level 3) |  |  |
Financial instruments owned: |  |  |
Total assets measured at fair value |  | 0 | 0
Fiduciary Assets: |  |  |
Fiduciary assets |  | 0 | 0
Liabilities: |  |  |
Total liabilities measured at fair value |  | 268 | 189
Money Market Funds |  |  |
Fiduciary Assets: |  |  |
Fiduciary assets |  | 69 | 111
Money Market Funds | Identical Assets (Level 1) |  |  |
Fiduciary Assets: |  |  |
Fiduciary assets |  | 69 | 111
Money Market Funds | Observable Inputs (Level 2) |  |  |
Fiduciary Assets: |  |  |
Fiduciary assets |  | 0 | 0
Money Market Funds | Unobservable Inputs (Level 3) |  |  |
Fiduciary Assets: |  |  |
Fiduciary assets |  | 0 | 0
Forward Contracts |  |  |
Liabilities: |  |  |
Foreign exchange forward contracts | [1] | 100 | 0
Forward Contracts | Identical Assets (Level 1) |  |  |
Liabilities: |  |  |
Foreign exchange forward contracts | [1] | 0 | 0
Forward Contracts | Observable Inputs (Level 2) |  |  |
Liabilities: |  |  |
Foreign exchange forward contracts | [1] | 0 | 0
Forward Contracts | Unobservable Inputs (Level 3) |  |  |
Liabilities: |  |  |
Foreign exchange forward contracts | [1] | 100 | 0
Other Assets |  |  |
Financial instruments owned: |  |  |
Exchange traded equity securities | [2] | 119 | 81
Mutual funds | [2] | 153 | 158
Other Assets | Identical Assets (Level 1) |  |  |
Financial instruments owned: |  |  |
Exchange traded equity securities | [2] | 119 | 81
Mutual funds | [2] | 153 | 158
Other Assets | Observable Inputs (Level 2) |  |  |
Financial instruments owned: |  |  |
Exchange traded equity securities | [2] | 0 | 0
Mutual funds | [2] | 0 | 0
Other Assets | Unobservable Inputs (Level 3) |  |  |
Financial instruments owned: |  |  |
Exchange traded equity securities | [2] | 0 | 0
Mutual funds | [2] | 0 | 0
Cash and Cash Equivalents |  |  |
Financial instruments owned: |  |  |
Money market funds | [3] | 31 | 143
Cash and Cash Equivalents | Identical Assets (Level 1) |  |  |
Financial instruments owned: |  |  |
Money market funds | [3] | 31 | 143
Cash and Cash Equivalents | Observable Inputs (Level 2) |  |  |
Financial instruments owned: |  |  |
Money market funds | [3] | 0 | 0
Cash and Cash Equivalents | Unobservable Inputs (Level 3) |  |  |
Financial instruments owned: |  |  |
Money market funds | [3] | 0 | 0
Other Receivables |  |  |
Financial instruments owned: |  |  |
Other equity investments | [2] | 8 | 0
Other Receivables | Identical Assets (Level 1) |  |  |
Financial instruments owned: |  |  |
Other equity investments | [2] | 0 | 0
Other Receivables | Observable Inputs (Level 2) |  |  |
Financial instruments owned: |  |  |
Other equity investments | [2] | 8 | 0
Other Receivables | Unobservable Inputs (Level 3) |  |  |
Financial instruments owned: |  |  |
Other equity investments | [2] | 0 | 0
Accounts Payable and Accrued Liabilities and Other Liabilities |  |  |
Liabilities: |  |  |
Contingent purchase consideration liability | [4] | 168 | 189
Accounts Payable and Accrued Liabilities and Other Liabilities | Identical Assets (Level 1) |  |  |
Liabilities: |  |  |
Contingent purchase consideration liability | [4] | 0 | 0
Accounts Payable and Accrued Liabilities and Other Liabilities | Observable Inputs (Level 2) |  |  |
Liabilities: |  |  |
Contingent purchase consideration liability | [4] | 0 | 0
Accounts Payable and Accrued Liabilities and Other Liabilities | Unobservable Inputs (Level 3) |  |  |
Liabilities: |  |  |
Contingent purchase consideration liability | [4] | $ 168 | $ 189
[1] | Included in accounts payable and accrued liabilities in the consolidated balance sheets.
[2] | Included in other assets in the consolidated balance sheets.
[3] | Included in cash and cash equivalents in the consolidated balance sheets.
[4] | Included in accounts payable and accrued liabilities and other liabilities in the consolidated balance sheets.

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