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Cash, Cash Equivalents and Short-Term Investments (Tables) | 12 Months Ended
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Dec. 31, 2020
Cash, Cash Equivalents and Short-Term Investments |
Schedule of cash, cash equivalents and short-term investments | Cash, cash equivalents and short-term investments consisted of the following as of December 31, 2019 and 2018 (in thousands): ​
​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | Carrying Value
​ |  | 2020 |  | 2019
Cash | ​ | $ | 25,053 | ​ | $ | 3,547
Cash equivalents: | ​ |  | ​ | ​ | ​ | ​
Money market mutual funds | ​ |  | 11,820 | ​ | ​ | 43,688
Total cash and cash equivalents | ​ |  | 36,873 | ​ | ​ | 47,235
Short-term investments: | ​ |  | ​ | ​ | ​ | ​
U.S. Treasury notes and bills | ​ |  | 23,309 | ​ | ​ | 21,094
Mutual funds | ​ |  | 33,135 | ​ | ​ | 25,967
Total short-term investments | ​ |  | 56,444 | ​ | ​ | 47,061
Cash, cash equivalents and short-term investments | ​ | $ | 93,317 | ​ | $ | 94,296
​
Schedule of available-for-sale debt securities | The amortized cost, gross unrealized gains, gross unrealized losses and fair value of available-for-sale debt securities by type of security at December 31, 2020 were as follows (in thousands): ​
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ |  | Amortized |  | Unrealized |  | Unrealized |  | ​ | ​
​ | ​ | Cost | ​ | Gains | ​ | Losses | ​ | Fair Value
U.S. Treasury notes | ​ | $ | 23,179 | ​ | $ | 173 | ​ | $ | (43) | ​ | $ | 23,309
Total available-for-sale investments | ​ | $ | 23,179 | ​ | $ | 173 | ​ | $ | (43) | ​ | $ | 23,309
​ The amortized cost, gross unrealized gains, gross unrealized losses and fair value of available-for-sale debt securities by type of security at December 31, 2019 were as follows (in thousands): ​
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ |  | Amortized |  | Unrealized |  | Unrealized |  | ​ | ​
​ | ​ | Cost | ​ | Gains | ​ | Losses | ​ | Fair Value
U.S. Treasury notes and bills | ​ | $ | 21,122 |  | $ | 26 |  | $ | (54) | ​ | $ | 21,094
Total available-for-sale investments | ​ | $ | 21,122 |  | $ | 26 | ​ | $ | (54) | ​ | $ | 21,094
​
Schedule of investments based on stated contractual maturities | The following table summarizes the fair value of available-for-sale debt securities based on stated contractual maturities as of December 31, 2020 (in thousands): ​
​ | ​ | ​ | ​ | ​ | ​ | ​
​ |  | Amortized Cost |  | Fair Value
Due within one year | ​ | $ | 14,084 | ​ | $ | 14,111
Due between one and two years | ​ |  | 9,095 | ​ |  | 9,198
​ | ​ | ​ | ​ | ​ | ​ | ​
Total | ​ | $ | 23,179 | ​ | $ | 23,309
​ The following table summarizes the fair value of available-for-sale debt securities based on stated contractual maturities as of December 31, 2019 (in thousands): ​
​ | ​ | ​ | ​ | ​ | ​ | ​
​ |  | Amortized Cost |  | Fair Value
Due within one year | ​ | $ | 12,044 |  | $ | 12,047
Due between one and two years | ​ |  | 9,078 |  |  | 9,047
Total | ​ | $ | 21,122 |  | $ | 21,094
​
Schedule of unrealized gains (losses) on investments | Unrealized gains (losses) during 2020 and 2019 related to equity securities held at December 31, 2020 and 2019 are as follows (in thousands): ​
​ | ​ | ​ | ​ | ​ | ​ | ​
​ |  | 2020 |  | 2019
Net losses recognized during the year on equity securities | ​ | $ | (245) | ​ | $ | (102)
Less: net losses recognized during the year on equity securities sold during the year | ​ |  | (1,090) | ​ | ​ | —
Unrealized gains (losses) recognized during the year on equity securities still held at December 31, 2020 and 2019 | ​ | $ | 845 | ​ | $ | (102)

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