Marketable Securities

12 Months Ended

Dec. 31, 2020

Investments, Debt and Equity Securities [Abstract]

Marketable Securities

Marketable Securities

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
Corporate debt securities	$	17,086	$	452	$	—	$	17,538
Tax-exempt municipal securities	19,924		365		—		20,289
Total	$	37,010	$	817	$	—	$	37,827

The following is a summary of available-for-sale securities as of December 31, 2019 (in thousands):

	Amortized Cost		Gross Unrealized Gain		Gross Unrealized (Losses)		Estimated Fair Value
Corporate debt securities	$	42,584	$	165	$	(40)	$	42,709
Tax-exempt municipal securities	23,301		112		(215)		23,198
Variable rate demand notes	5,600		—		—		5,600
Total	$	71,485	$	277	$	(255)	$	71,507

The unrealized gains and losses on the Company’s investments in corporate debt and municipal securities as of December 31, 2019 and 2020 were caused by changes in market values primarily due to interest rate changes. As of December 31, 2020, 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 years ended December 31, 2018, 2019, and 2020.

The following table summarizes the maturities of the Company’s marketable securities as of December 31, 2019 and 2020 (in thousands):

	December 31, 2019		December 31, 2020
Due within one year	$	34,874	$	7,557
Due after one year through five years	36,633		30,270
Total	$	71,507	$	37,827

The following table summarizes the proceeds from the maturities and sales of available-for-sale securities for the years ended December 31, 2018, 2019, and 2020 (in thousands):

	December 31, 2018		December 31, 2019		December 31, 2020
Maturities of marketable securities	$	16,367	$	43,762	$	34,728
Sales of marketable securities	—		—		1,464
Total	$	16,367	$	43,762	$	36,192

The Company recorded approximately $35,000 in gross realized gains in net income during the year ended December 31, 2020. The Company did not record any gross realized gains or losses in net income during the years ended December 31, 2019 and 2018.