10.Cash, Cash Equivalents and Short-Term Investments

​

Cash, cash equivalents and short-term investments consisted of the following (in thousands):

​

​

Cash equivalents and short-term investments include the following securities with gross unrealized gains and losses (in thousands):

​

​

As of September 30, 2021 and December 31, 2020, our cash equivalents and short-term investments had a weighted-average time to maturity of approximately 227 days and 78 days, respectively. Our short-term investments are classified as available-for-sale securities. Accordingly, we have classified certain securities as short-term investments on our balance sheets as they are available for use in the current operations. As of September 30, 2021, we had no

investments that had been in a continuous unrealized loss position for more than 12 months. As of September 30, 2021, a total of 19 individual securities had been in an unrealized loss position for 12 months or less, and the losses were determined to be temporary. The gross unrealized losses above were caused by interest rate increases. No significant facts or circumstances have arisen to indicate that there has been any significant deterioration in the creditworthiness of the issuers of the securities held by us. Based on our review of these securities, including the assessment of the duration and severity of the unrealized losses and our ability and intent to hold the investments until maturity, there were no other-than-temporary impairments for these securities as of September 30, 2021.

​

The following table shows the fair value and gross unrealized losses of our investments in individual securities that are in an unrealized loss position, aggregated by investment category (in thousands):

​

​