The marketable securities are classified as available-for-sale and consist of U.S. treasury securities and corporate notes. The fair value measurement data for marketable securities is obtained from independent pricing services. The Company validates the prices provided by the third-party pricing services by understanding the valuation methods and data sources used and analyzing the pricing data in certain instances.

The Company had no marketable securities at September 30, 2021. The following table summarizes the marketable securities (in thousands):


As of December 31, 2020	Amortized Cost		Unrealized Gains		Unrealized Losses		Fair Value
U.S. treasury securities	$	10,003	$	3	$	—	$	10,006
Corporate notes		14,522		50		—		14,572
Total marketable securities, current	$	24,525	$	53	$	—	$	24,578

All marketable securities held at December 31, 2020 had effective maturities of less than one year. There were no realized gains or losses recognized on the sale or maturity of available-for-sale debt securities during the three and nine months ended September 30, 2021, respectively and, as a result, the Company did not reclassify any amounts out of accumulated comprehensive loss. As of September 30, 2021 and December 31, 2020, the Company had no allowance for credit losses for available-for-sale debt securities. There were no impairment charges or recoveries recorded during each of the nine months ended September 30, 2021 and September 30, 2020, respectively.