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v3.20.2

Marketable Securities (Tables) | 12 Months Ended
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Dec. 31, 2019
Investments, Debt and Equity Securities [Abstract] |
Schedule for Available-for-Sale Securities | The following is a summary of available-for-sale securities as of December 31, 2019 (in thousands): ​
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ |  | ​ | ​ |  | Gross |  | Gross Unrealized |  | Estimated Fair
​ | ​ | Amortized Cost | ​ | Unrealized Gain | ​ | (Losses) | ​ | Value
Corporate debt securities | ​ | $ | 42,584 | ​ | $ | 165 | ​ | $ | (40) | ​ | $ | 42,709
Tax-exempt municipal securities | ​ |  | 23,301 | ​ |  | 112 | ​ |  | (215) | ​ |  | 23,198
Variable rate demand notes | ​ |  | 5,600 | ​ |  | — | ​ |  | — | ​ |  | 5,600
Total | ​ | $ | 71,485 | ​ | $ | 277 | ​ | $ | (255) | ​ | $ | 71,507
​ The following is a summary of available-for-sale securities as of December 31, 2018 (in thousands): ​
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ |  | ​ | ​ |  | Gross |  | Gross Unrealized |  | Estimated Fair
​ | ​ | Amortized Cost | ​ | Unrealized Gain | ​ | (Losses) | ​ | Value
Corporate debt securities | ​ | $ | 48,202 | ​ | $ | 12 | ​ | $ | (284) | ​ | $ | 47,930
Tax-exempt municipal securities | ​ |  | 22,858 | ​ |  | 45 | ​ |  | (34) | ​ |  | 22,869
Variable rate demand notes | ​ |  | 4,000 | ​ |  | — | ​ |  | — | ​ |  | 4,000
Total | ​ | $ | 75,060 | ​ | $ | 57 | ​ | $ | (318) | ​ | $ | 74,799
Schedule of Maturities of Marketable Securities | The following table summarizes the maturities of the Company’s marketable securities as of December 31, 2018 and 2019 (in thousands): ​
​ | ​ | ​ | ​ | ​ | ​ | ​
​ |  | December 31, 2018 |  | December 31, 2019
Due within one year | ​ | $ | 37,121 | ​ | $ | 34,874
Due after one year through five years | ​ |  | 37,678 | ​ |  | 36,633
Total | ​ | $ | 74,799 | ​ | $ | 71,507

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