Marketable Securities

3 Months Ended

Mar. 31, 2020

Investments, Debt and Equity Securities [Abstract]

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



	Amortized Cost		Gross Unrealized Gain		Gross Unrealized (Losses)			Estimated Fair Value
Corporate debt securities	$	34,457	$	62	$	(160	)	$	34,359
Tax-exempt municipal securities	23,321		221		(69		)	23,473
Variable rate demand notes	5,600		—		—			5,600
Total	$	63,378	$	283	$	(229	)	$	63,432

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 March 31, 2020 were caused by changes in market values primarily due to interest rate changes. As of March 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 three months ended March 31, 2019 and 2020.

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



	December 31, 2019		March 31, 2020
Due within one year	$	34,874	$	26,842
Due after one year through five years	36,633		36,590
Total	$	71,507	$	63,432

Amounts due within one year in the table above included $5.6 million of variable rate demand notes, which have contractual maturities ranging from 17 years to 26 years as of March 31, 2020. The variable rate demand notes are floating rate municipal bonds with embedded put options that allow the Company to sell the security at par plus accrued interest on a settlement basis ranging from one day to seven days. The Company has classified these securities based on their effective maturity dates, which range from one day to seven days from the balance sheet date.

The Company received $12.9 million and $9.9 million of proceeds from the maturities of available-for-sale securities during the three months ended March 31, 2019 and 2020, respectively. The Company did not record any gross realized gains or losses in net income during the three months ended March 31, 2019 and 2020. Additionally, there were no proceeds from sales of marketable securities prior to maturity during the three months ended March 31, 2019 and 2020.