Financial Instruments (Tables)

6 Months Ended

Jun. 30, 2022

Financial Instruments

Schedule of available-for-sale securities

	June 30, 2022						December 31, 2021
	Amortized Cost		Gross Unrealized Loss		Estimated Fair Value		Amortized Cost		Gross Unrealized Gain		Gross Unrealized Loss		Estimated Fair Value
	(in thousands)
Money market deposits	$	40,268	$	—	$	40,268	$	10,041	$	—	$	—	$	10,041
U.S. Treasury securities (1)		459,509		(12,505)		447,004		689,640		1,081		(2,624)		688,097
Corporate bonds and notes (1)		34,280		(839)		33,441		52,729		—		(392)		52,337
Municipal securities		69,749		(2,841)		66,908		89,814		261		(613)		89,462
Total	$	603,806	$	(16,185)	$	587,621	$	842,224	$	1,342	$	(3,629)	$	839,937
Classified as:
Cash equivalents (2)						40,268								10,041
Short-term investments						547,353								829,896
Total					$	587,621							$	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

	June 30, 2022
	Amortized Cost		Fair Value
	(in thousands)
Less than or equal to one year	$	187,392	$	184,947
Greater than one year but less than five years		376,146		362,406
Total	$	563,538	$	547,353