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Fair Value Measurements (Assets And Liabilities Measured At Fair Value On A Recurring Basis) (Details) - USD ($) $ in Millions | Dec. 31, 2018 | Dec. 31, 2017
--- | --- | ---
Financial instruments owned: |  |  |
Total assets measured at fair value |  | $ 14,378 | $ 16,176
Fair Value, Measurements, Recurring |  |  |
Financial instruments owned: |  |  |
Total assets measured at fair value |  | 410 | 382
Fiduciary Assets: |  |  |
Fiduciary assets |  | 100 | 111
Liabilities: |  |  |
Total liabilities measured at fair value |  | 624 | 189
Identical Assets (Level 1) |  |  |
Financial instruments owned: |  |  |
Total assets measured at fair value |  | 2,970 | 2,586
Identical Assets (Level 1) | Fair Value, Measurements, Recurring |  |  |
Financial instruments owned: |  |  |
Total assets measured at fair value |  | 402 | 382
Fiduciary Assets: |  |  |
Fiduciary assets |  | 100 | 111
Liabilities: |  |  |
Total liabilities measured at fair value |  | 0 | 0
Observable Inputs (Level 2) |  |  |
Financial instruments owned: |  |  |
Total assets measured at fair value |  | 4,261 | 4,238
Observable Inputs (Level 2) | Fair Value, Measurements, Recurring |  |  |
Financial instruments owned: |  |  |
Total assets measured at fair value |  | 8 | 0
Fiduciary Assets: |  |  |
Fiduciary assets |  | 0 | 0
Liabilities: |  |  |
Total liabilities measured at fair value |  | 116 | 0
Unobservable Inputs (Level 3) |  |  |
Financial instruments owned: |  |  |
Total assets measured at fair value |  | 334 | 372
Unobservable Inputs (Level 3) | Fair Value, Measurements, Recurring |  |  |
Financial instruments owned: |  |  |
Total assets measured at fair value |  | 0 | 0
Fiduciary Assets: |  |  |
Fiduciary assets |  | 0 | 0
Liabilities: |  |  |
Total liabilities measured at fair value |  | 508 | 189
Other Assets | Fair Value, Measurements, Recurring |  |  |
Financial instruments owned: |  |  |
Exchange traded equity securities | [1] | 133 | 81
Mutual funds | [1] | 151 | 158
Other Assets | Identical Assets (Level 1) | Fair Value, Measurements, Recurring |  |  |
Financial instruments owned: |  |  |
Exchange traded equity securities | [1] | 133 | 81
Mutual funds | [1] | 151 | 158
Other Assets | Observable Inputs (Level 2) | Fair Value, Measurements, Recurring |  |  |
Financial instruments owned: |  |  |
Exchange traded equity securities | [1] | 0 | 0
Mutual funds | [1] | 0 | 0
Other Assets | Unobservable Inputs (Level 3) | Fair Value, Measurements, Recurring |  |  |
Financial instruments owned: |  |  |
Exchange traded equity securities | [1] | 0 | 0
Mutual funds | [1] | 0 | 0
Cash and Cash Equivalents | Fair Value, Measurements, Recurring |  |  |
Financial instruments owned: |  |  |
Money market funds | [2] | 118 | 143
Cash and Cash Equivalents | Identical Assets (Level 1) | Fair Value, Measurements, Recurring |  |  |
Financial instruments owned: |  |  |
Money market funds | [2] | 118 | 143
Cash and Cash Equivalents | Observable Inputs (Level 2) | Fair Value, Measurements, Recurring |  |  |
Financial instruments owned: |  |  |
Money market funds | [2] | 0 | 0
Cash and Cash Equivalents | Unobservable Inputs (Level 3) | Fair Value, Measurements, Recurring |  |  |
Financial instruments owned: |  |  |
Money market funds | [2] | 0 | 0
Other Receivables | Fair Value, Measurements, Recurring |  |  |
Financial instruments owned: |  |  |
Other equity investment | [1] | 8 | 0
Other Receivables | Identical Assets (Level 1) | Fair Value, Measurements, Recurring |  |  |
Financial instruments owned: |  |  |
Other equity investment | [1] | 0 | 0
Other Receivables | Observable Inputs (Level 2) | Fair Value, Measurements, Recurring |  |  |
Financial instruments owned: |  |  |
Other equity investment | [1] | 8 | 0
Other Receivables | Unobservable Inputs (Level 3) | Fair Value, Measurements, Recurring |  |  |
Financial instruments owned: |  |  |
Other equity investment | [1] | 0 | 0
Accounts Payable and Accrued Liabilities and Other Liabilities | Fair Value, Measurements, Recurring |  |  |
Liabilities: |  |  |
Contingent purchase consideration liability | [3] | 183 | 189
Accounts Payable and Accrued Liabilities and Other Liabilities | Identical Assets (Level 1) | Fair Value, Measurements, Recurring |  |  |
Liabilities: |  |  |
Contingent purchase consideration liability | [3] | 0 | 0
Accounts Payable and Accrued Liabilities and Other Liabilities | Observable Inputs (Level 2) | Fair Value, Measurements, Recurring |  |  |
Liabilities: |  |  |
Contingent purchase consideration liability | [3] | 0 | 0
Accounts Payable and Accrued Liabilities and Other Liabilities | Unobservable Inputs (Level 3) | Fair Value, Measurements, Recurring |  |  |
Liabilities: |  |  |
Contingent purchase consideration liability | [3] | 183 | 189
Money Market Funds | Fair Value, Measurements, Recurring |  |  |
Fiduciary Assets: |  |  |
Fiduciary assets |  | 80 | 111
Money Market Funds | Identical Assets (Level 1) | Fair Value, Measurements, Recurring |  |  |
Fiduciary Assets: |  |  |
Fiduciary assets |  | 80 | 111
Money Market Funds | Observable Inputs (Level 2) | Fair Value, Measurements, Recurring |  |  |
Fiduciary Assets: |  |  |
Fiduciary assets |  | 0 | 0
Money Market Funds | Unobservable Inputs (Level 3) | Fair Value, Measurements, Recurring |  |  |
Fiduciary Assets: |  |  |
Fiduciary assets |  | 0 | 0
US Treasury Bills | Fair Value, Measurements, Recurring |  |  |
Fiduciary Assets: |  |  |
Fiduciary assets |  | 20 | 0
US Treasury Bills | Identical Assets (Level 1) | Fair Value, Measurements, Recurring |  |  |
Fiduciary Assets: |  |  |
Fiduciary assets |  | 20 | 0
US Treasury Bills | Observable Inputs (Level 2) | Fair Value, Measurements, Recurring |  |  |
Fiduciary Assets: |  |  |
Fiduciary assets |  | 0 | 0
US Treasury Bills | Unobservable Inputs (Level 3) | Fair Value, Measurements, Recurring |  |  |
Fiduciary Assets: |  |  |
Fiduciary assets |  | 0 | 0
Senior Debt Obligations Due 2014 | Long-term Debt | Fair Value, Measurements, Recurring |  |  |
Liabilities: |  |  |
Acquisition related derivative contract |  | 441 | 0
Senior Debt Obligations Due 2014 | Long-term Debt | Identical Assets (Level 1) | Fair Value, Measurements, Recurring |  |  |
Liabilities: |  |  |
Acquisition related derivative contract |  | 0 | 0
Senior Debt Obligations Due 2014 | Long-term Debt | Observable Inputs (Level 2) | Fair Value, Measurements, Recurring |  |  |
Liabilities: |  |  |
Acquisition related derivative contract |  | 116 | 0
Senior Debt Obligations Due 2014 | Long-term Debt | Unobservable Inputs (Level 3) | Fair Value, Measurements, Recurring |  |  |
Liabilities: |  |  |
Acquisition related derivative contract |  | $ 325 | $ 0
[1] | Included in other assets in the consolidated balance sheets.
[2] | Included in cash and cash equivalents in the consolidated balance sheets.
[3] | Included in accounts payable and accrued liabilities and other liabilities in the consolidated balance sheets.

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