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Investments in Marketable Securities (Tables) | 9 Months Ended
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Sep. 30, 2018
Marketable Securities [Abstract] |
Schedule of Investments in Marketable Securities | The following is a summary of the cost, gross unrealized gains and losses and fair value of Investments in marketable securities:
| December 31, 2017 |  | September 30, 2018
Cost | $ | 67.1 |  |  | $ | 128.3 |
Unrealized gains | 13.0 |  |  | 15.8 |
Unrealized losses | (2.3 | ) |  | (0.0 | )
Fair value | $ | 77.8 |  |  | $ | 144.1 |

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- Definition Tabular disclosure of marketable securities. This may consist of investments in certain debt and equity securities, short-term investments and other assets. + References No definition available. + Details
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