Note 7. Cash, Cash Equivalents and Short-Term Investments

Cash, cash equivalents and short-term investments consisted of the following as of March 31, 2025 and December 31, 2024 (in thousands):

​

​

Available-for-sale investments

The amortized cost, gross unrealized gains, gross unrealized losses and fair value of available-for-sale investments by type of security at March 31, 2025 were as follows (in thousands):

​

​

The following table summarizes the fair value of available-for-sale investments based on stated contractual maturities as of March 31, 2025:

​

​

The amortized cost, gross unrealized gains, gross unrealized losses and fair value of available-for-sale investments by type of security at December 31, 2024 were as follows (in thousands):

​

​

The following table summarizes the fair value of available-for-sale investments based on stated contractual maturities as of December 31, 2024:

​

​

The primary objective of our investment portfolio is to enhance overall returns in an efficient manner while maintaining safety of principal, prudent levels of liquidity and acceptable levels of risk. Our investment policy limits interest-bearing security investments to certain types of debt and money market instruments issued by institutions with primarily investment-grade credit ratings, and it places restrictions on maturities and concentration by asset class and issuer.

We review our available-for-sale investments for other-than-temporary declines in fair value below our cost basis each quarter and whenever events or changes in circumstances indicate that the cost basis of an asset may not be recoverable. The evaluation is based on a number of factors, including the length of time and the extent to which the fair value has been below our cost basis, as well as adverse conditions related specifically to the security such as any changes to the credit rating of the security and the intent to sell or whether we will more likely than not be required to sell the security before recovery of its amortized cost basis. Our assessment of whether a security is other-than-temporarily impaired could change in the future based on new developments or changes in assumptions related to that particular security.

The following table shows the Company’s gross unrealized losses and fair value of available-for-sale debt securities, aggregated by investment category and length of time that individual securities have been in a continuous unrealized loss position at March 31, 2025:

​

For U.S. Treasury notes, the unrealized losses were caused by interest rate increases. The contractual terms of those investments do not permit the issuer to settle the securities at a price less than the amortized cost of the investment. Because the Company does not intend to sell the investments and it is not more likely than not that the Company will be required to sell the investments before recovery of their amortized cost bases, which may be maturity, the Company does not consider the U.S. Treasury notes to be other-than-temporarily impaired at March 31, 2025. For corporate debt securities, the unrealized losses were primarily caused by interest rate increases. The Company does not intend to sell these debt securities that are in an unrealized loss position, and it is not more likely than not that the Company will be required to sell these debt securities before recovery of their amortized cost bases, which may be at maturity. Based on the credit quality of the debt securities, and the Company’s estimates of future cash flows to be collected from those securities, the Company believes the unrealized losses are not credit losses. Accordingly, the Company does not consider the corporate debt securities to be other-than-temporarily impaired at March 31, 2025.

During the three months ended March 31, 2025 and 2024, we had realized gains (losses) of ($0.9) million and $2.4 million on available-for-sale investments, respectively.

Equity Investments

We held investments in equity securities with readily determinable fair values of $98.3 million at March 31, 2025. These investments consist of mutual funds that invest primarily in tax-free municipal bonds and treasury inflation protected securities.

Unrealized gains (losses) during the three months ended March 31, 2025 and 2024 related to equity securities held at March 31, 2025 and 2024 are as follows (in thousands):

​

​