Financial Instruments (Tables)

3 Months Ended

Mar. 31, 2022

Financial Instruments

Schedule of available-for-sale securities

	March 31, 2022								December 31, 2021
	Amortized Cost		Gross Unrealized Gain		Gross Unrealized Loss		Estimated Fair Value		Amortized Cost		Gross Unrealized Gain		Gross Unrealized Loss		Estimated Fair Value
	(in thousands)
Money market deposits		56,374		—		—		56,374		10,041		—		—		10,041
U.S. Treasury securities (1)		485,265		—		(10,416)		474,849		689,640		1,081		(2,624)		688,097
Corporate bonds and notes (1)		46,499		—		(833)		45,666		52,729		—		(392)		52,337
Municipal securities		75,667		3		(2,525)		73,145		89,814		261		(613)		89,462
Total	$	663,805	$	3	$	(13,774)	$	650,034	$	842,224	$	1,342	$	(3,629)	$	839,937
Classified as:
Cash equivalents (2)								56,374								10,041
Short-term investments								593,660								829,896
Total							$	650,034							$	839,937

(1) Per the Company’s investment policy, all U.S. Treasury securities and debt securities are classified as short-term investments irrespective of holding period.  

(2) Cash equivalents includes cash sweep accounts and U.S. Treasury money market mutual funds.

Summarized portfolio of available-for-sale securities by contractual maturity

	March 31, 2022
	Amortized Cost		Fair Value
	(in thousands)
Less than or equal to one year	$	161,807	$	160,782
Greater than one year but less than five years		445,624		432,878
Total	$	607,431	$	593,660