4. Cash Equivalents and Marketable Securities

Cash equivalents and marketable securities consisted of the following:

As of March 31, 2021 and December 31, 2020, $74.6 million and zero, respectively, of marketable securities had maturities of more than one year and are classified as long-term assets.

There were $84.6 million and $14.7 million of investments in an unrealized loss position of $64,000 and $3,000 as of March 31, 2021 and December 31, 2020, respectively. During the three months ended March 31, 2021 and 2020, the Company did not record any other-than-temporary impairment charges on its available-for-sale securities. Based upon the Company’s impairment review, the Company determined that the unrealized losses were not attributed to credit risk but were primarily associated with changes in interest rates. Based on the scheduled maturities of the investments, the Company was more likely than not to hold these investments for a period of time sufficient for a recovery of the Company’s cost basis.  As such, the Company concluded that the unrealized losses in the investment securities were not other-than-temporary.