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Investments in Marketable Securities | 12 Months Ended
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Dec. 31, 2018
Marketable Securities [Abstract] |
Investments in Marketable Securities | Investments in Marketable Securities Investments in marketable securities at December 31, 2017 and 2018 were $77.8 million and $119.3 million, respectively. The following is a summary of the cost, gross unrealized gains and losses and fair value of Investments in marketable securities:
|  | December 31,
|  | 2017 |  | 2018
Cost |  | $ | 67.1 |  |  | $ | 126.8 |
Unrealized gains |  | 13.0 |  |  | 1.1 |
Unrealized losses |  | (2.3 | ) |  | (8.6 | )
Fair value |  | $ | 77.8 |  |  | $ | 119.3 |
For the years ended December 31, 2017 and 2018, the Company received proceeds of $112.2 million and $81.4 million, respectively, from the sale of investments in marketable securities and recorded net gains of $35.8 million and $6.9 million, respectively.

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- Definition The entire disclosure for investments in certain debt and equity securities. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 320 -URI http://asc.fasb.org/subtopic&trid=2209399 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 946 -SubTopic 320 -URI http://asc.fasb.org/subtopic&trid=2324412 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -URI http://asc.fasb.org/topic&trid=2196928 Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 940 -SubTopic 320 -URI http://asc.fasb.org/subtopic&trid=2176304 + Details
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