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Fair Value Measurements - Assets and Liabilities Measured on a Recurring Basis (Details) - USD ($) $ in Millions | Sep. 30, 2017 | Dec. 31, 2016 | Sep. 30, 2016
--- | --- | --- | ---
Investments in marketable securities |  |  |  |
Trading securities |  | $ 51.1 |  | $ 40.5
Fair Value Measured On A Recurring Basis |  |  |  |
Financial Assets |  |  |  |
Cash equivalents |  | 35.1 | $ 64.1 |
Investments in marketable securities |  |  |  |
Trading securities | [1] | 51.1 | 40.5 |
Available-for-sale securities | [1] | 41.3 | 81.9 |
Other investments |  |  | 3.4 |
Foreign currency forward contracts | [2] | 0.7 | 0.6 |
Financial Liabilities |  |  |  |
Contingent payment arrangements | [2] | 8.1 | 8.6 |
Affiliate equity obligations | [2] | 45.7 | 12.1 |
Foreign currency forward contracts | [2] | 1.0 | 0.5 |
Fair Value Measured On A Recurring Basis | Quoted Prices in Active Markets for Identical Assets (Level 1) |  |  |  |
Financial Assets |  |  |  |
Cash equivalents |  | 35.1 | 64.1 |
Investments in marketable securities |  |  |  |
Trading securities | [1] | 51.1 | 40.5 |
Available-for-sale securities | [1] | 41.3 | 81.9 |
Other investments |  |  | 3.4 |
Foreign currency forward contracts | [2] | 0.0 | 0.0 |
Financial Liabilities |  |  |  |
Contingent payment arrangements | [2] | 0.0 | 0.0 |
Affiliate equity obligations | [2] | 0.0 | 0.0 |
Foreign currency forward contracts | [2] | 0.0 | 0.0 |
Fair Value Measured On A Recurring Basis | Significant Other Observable Inputs (Level 2) |  |  |  |
Financial Assets |  |  |  |
Cash equivalents |  | 0.0 | 0.0 |
Investments in marketable securities |  |  |  |
Trading securities | [1] | 0.0 | 0.0 |
Available-for-sale securities | [1] | 0.0 | 0.0 |
Other investments |  |  | 0.0 |
Foreign currency forward contracts | [2] | 0.7 | 0.6 |
Financial Liabilities |  |  |  |
Contingent payment arrangements | [2] | 0.0 | 0.0 |
Affiliate equity obligations | [2] | 0.0 | 0.0 |
Foreign currency forward contracts | [2] | 1.0 | 0.5 |
Fair Value Measured On A Recurring Basis | Significant Other Unobservable Inputs (Level 3) |  |  |  |
Financial Assets |  |  |  |
Cash equivalents |  | 0.0 | 0.0 |
Investments in marketable securities |  |  |  |
Trading securities | [1] | 0.0 | 0.0 |
Available-for-sale securities | [1] | 0.0 | 0.0 |
Other investments |  |  | 0.0 |
Foreign currency forward contracts | [2] | 0.0 | 0.0 |
Financial Liabilities |  |  |  |
Contingent payment arrangements | [2] | 8.1 | 8.6 |
Affiliate equity obligations | [2] | 45.7 | 12.1 |
Foreign currency forward contracts | [2] | $ 0.0 | $ 0.0 |
[1] | Principally investments in equity securities.
[2] | Amounts are presented within Other assets or Other liabilities.

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