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Marketable Securities (Tables) | 3 Months Ended
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Mar. 31, 2021
Marketable Securities |
Schedule of marketable securities | ​
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | ​ | ​ | ​ | Gross | ​ | Gross | ​ | ​ | ​
​ |  | Amortized |  | Unrealized | ​ | Unrealized |  | ​
March 31, 2021 | ​ | Cost | ​ | Gains | ​ | Losses | ​ | Fair Value
(in thousands) | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
Money Market Funds | ​ | $ | 165,350 | ​ | $ | — | ​ | $ | — | ​ | $ | 165,350
Corporate Securities | ​ | ​ | 73,922 | ​ | ​ | 12 | ​ | ​ | (5) | ​ | ​ | 73,929
Government Securities | ​ | ​ | 319,931 | ​ | ​ | 107 | ​ | ​ | (7) | ​ | ​ | 320,031
​ | ​ | $ | 559,203 | ​ | $ | 119 | ​ | $ | (12) | ​ | $ | 559,310
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
Reported as | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
Cash and cash equivalents | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | $ | 165,350
Marketable securities | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | 393,960
Total investments | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | $ | 559,310
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | ​ | ​ | ​ | Gross | ​ | Gross | ​ | ​ | ​
​ |  | Amortized |  | Unrealized | ​ | Unrealized |  | ​
December 31, 2020 | ​ | Cost | ​ | Gains | ​ | Losses | ​ | Fair Value
(in thousands) | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
Money Market Funds | ​ | $ | 158,937 | ​ | $ | — | ​ | $ | — | ​ | $ | 158,937
Corporate Securities | ​ | ​ | 119,782 | ​ | ​ | 57 | ​ | ​ | (6) | ​ | ​ | 119,833
Government Securities | ​ | ​ | 315,319 | ​ | ​ | 37 | ​ | ​ | (3) | ​ | ​ | 315,353
​ | ​ | $ | 594,038 | ​ | $ | 94 | ​ | $ | (9) | ​ | $ | 594,123
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
Reported as | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
Cash and cash equivalents | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | $ | 158,937
Marketable securities | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | 435,186
Total investments | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | $ | 594,123
Schedule of maturities of marketable securities | ​
​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | Amortized |  | Estimated
March 31, 2021 | ​ | Cost | ​ | Fair Value
(in thousands) | ​ | ​ | ​ | ​ | ​ | ​
Mature in one year or less | ​ | $ | 368,762 | ​ | $ | 368,878
Mature within two years | ​ | ​ | 25,091 | ​ | ​ | 25,082
​ | ​ | $ | 393,853 | ​ | $ | 393,960
Schedule of unrealized losses on available-for-sale investments | ​ The unrealized losses on available-for-sale investments and their related fair values as of March 31, 2021 and December 31, 2020 are as follows: ​
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | Less than 12 months | ​ | 12 months or greater
​ | ​ | ​ | ​ | ​ | Unrealized | ​ | ​ | ​ | ​ | Unrealized
March 31, 2021 | ​ | Fair value | ​ | losses | ​ | Fair value | ​ | losses
(in thousands) | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
Corporate Securities | ​ | $ | 4,102 | ​ | $ | (2) | ​ | $ | 3,066 | ​ | $ | (3)
Government Securities | ​ | ​ | — | ​ | ​ | — | ​ | ​ | 14,990 | ​ | ​ | (7)
​ | ​ | $ | 4,102 | ​ | $ | (2) | ​ | $ | 18,056 | ​ | $ | (10)
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | Less than 12 months | ​ | 12 months or greater
​ | ​ | ​ | ​ | ​ | Unrealized | ​ | ​ | ​ | ​ | Unrealized
December 31, 2020 | ​ | Fair value | ​ | losses | ​ | Fair value | ​ | losses
(in thousands) | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
Corporate Securities | ​ | $ | 15,843 | ​ | $ | (6) | ​ | $ | — | ​ | $ | —
Government Securities | ​ | ​ | 40,802 | ​ | ​ | (3) | ​ | ​ | — | ​ | ​ | —
​ | ​ | $ | 56,645 | ​ | $ | (9) | ​ | $ | — | ​ | $ | —
Schedule of net gains and losses | ​
​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | Three Months Ended
​ | ​ | March 31,
​ |  | 2021 |  | 2020
Net gains (losses) recognized on equity securities | ​ | $ | 12,981 | ​ | $ | (2,336)
Less: net gains recognized on equity securities redeemed | ​ |  | (1) | ​ |  | —
Unrealized gains (losses) recognized on equity securities | ​ | $ | 12,980 | ​ | $ | (2,336)

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- Definition For all investments in an unrealized loss position, including those for which other-than-temporary impairments have not been recognized in earnings (including investments for which a portion of an other-than-temporary impairment has been recognized in other comprehensive income), a tabular disclosure of the aggregate related fair value of investments with unrealized losses and the aggregate amount of unrealized losses (that is, the amount by which amortized cost basis exceeds fair value). + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 6 -URI http://asc.fasb.org/extlink&oid=121645371&loc=d3e27290-111563 + Details
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