Marketable Securities

9 Months Ended

Sep. 30, 2021

Investments, Debt and Equity Securities [Abstract]

The following is a summary of available-for-sale securities as of September 30, 2021 (in thousands):


	Amortized Cost		Gross Unrealized Gain		Gross Unrealized (Losses)		Estimated Fair Value
Tax-exempt municipal securities	$	18,520	$	465	$	—	$	18,985
Corporate debt securities	10,940		274		—		11,214
Total	$	29,460	$	739	$	—	$	30,199

The following is a summary of available-for-sale securities as of December 31, 2020 (in thousands):


	Amortized Cost		Gross Unrealized Gain		Gross Unrealized (Losses)		Estimated Fair Value
Tax-exempt municipal securities	$	19,924	$	365	$	—	$	20,289
Corporate debt securities	17,086		452		—		17,538
Total	$	37,010	$	817	$	—	$	37,827

The unrealized gains on the Company’s investments in corporate debt and municipal securities as of December 31, 2020 and September 30, 2021 were caused by changes in market values primarily due to interest rate changes. As of September 30, 2021, there were no securities in an unrealized loss position for a period longer than twelve months. The Company has no allowance for credit losses related to its available-for-sale securities as all investments are in investment grade securities. The Company does not intend to sell these securities, and it is not more likely than not that the Company will be required to sell these securities prior to the recovery of their amortized cost basis, which may be at maturity. No impairment charges were recorded during the three and nine months ended September 30, 2020 and 2021.

The following table summarizes the maturities of the Company’s marketable securities as of December 31, 2020 and September 30, 2021 (in thousands):


	December 31, 2020		September 30, 2021
Due within one year	$	7,557	$	2,632
Due after one year through five years	30,270		27,567
Total	$	37,827	$	30,199

The following table summarizes the proceeds from the maturities and sales of available-for-sale securities for the three and nine months ended September 30, 2020 and 2021 (in thousands):


	For the three months ended September 30,				For the nine months ended September 30,
	2020		2021		2020		2021
Maturities of marketable securities	$	3,999	$	1,900	$	21,404	$	7,495
Sales of marketable securities	—		1,805		1,464		1,805
Total	$	3,999	$	3,705	$	22,868	$	9,300

The Company recorded approximately $35,000 in gross realized gains in net income during the nine months ended September 30, 2020 and approximately $0.8 million in gross realized losses in net income during the three and nine months ended September 30, 2021 related to the sales of marketable securities.