Cash, Cash Equivalents and Investments

3 Months Ended

Mar. 31, 2021

Cash and Cash Equivalents [Abstract]

Cash, Cash Equivalents and Investments

3. Cash, Cash Equivalents and Investments

The following tables summarize our cash, cash equivalents, and held-to-maturity investments at March 31, 2021 and December 31, 2020 (in thousands):

	As of March 31, 2021
			Gross		Gross				Cash and
	Amortized		Unrealized		Unrealized				Cash		Short-Term		Long-Term
	Cost		Gains		Losses		Fair Value		Equivalents		Investments		Investments
Cash	$	137,003	$	—	$	—	$	137,003	$	137,003	$	—	$	—
Level 1:
Money market funds		16,819		—		—		16,819		16,819		—		—
Agency bonds		73,996		94		—		74,090		—		45,995		28,001
Treasury bills		104,184		13		—		104,197		—		104,184		—
Subtotal		194,999		107		—		195,106		16,819		150,179		28,001
Level 2:
State and municipal obligations		83,086		12		(30)		83,068		—		74,295		8,791
Certificates of deposit		500		—		—		500		—		500		—
Corporate bonds		186,406		140		(81)		186,465		1,002		143,712		41,692
Treasury inflation-protected securities		3,310		7		—		3,317		—		3,310		—
Commercial paper		68,961		—		—		68,961		—		68,961		—
Subtotal		342,263		159		(111)		342,311		1,002		290,778		50,483
Total	$	674,265	$	266	$	(111)	$	674,420	$	154,824	$	440,957	$	78,484

Because we do not have any history of losses for our held-to-maturity investments, our expected credit loss allowance methodology for held-to-maturity investments is developed using published or estimated credit default rates for similar investments and current and future economic and market conditions. At March 31, 2021 and December 31, 2020, our credit loss reserve for held-to-maturity investments was approximately $0.1 million and $0.1 million, respectively.

	As of December 31, 2020
			Gross		Gross				Cash and
	Amortized		Unrealized		Unrealized				Cash		Short-Term		Long-Term
	Cost		Gains		Losses		Fair Value		Equivalents		Investments		Investments
Cash	$	116,107	$	—	$	—	$	116,107	$	116,107	$	—	$	—
Level 1:
Money market funds		23,611		—		—		23,611		23,611		—		—
Agency bonds		63,794		122		—		63,916		—		23,794		40,000
Treasury Bills		96,384		6		—		96,390				96,384
Subtotal		183,789		128		—		183,917		23,611		120,178		40,000
Level 2:
State and municipal obligations		77,130		25		(28)		77,127		—		66,519		10,611
Certificates of deposit		500		—		—		500		—		500		—
Corporate bonds		212,825		232		(100)		212,957		2,525		170,205		40,095
U.S. Treasury repurchase agreements		13,200		—		—		13,200		13,200		—		—
Treasury inflation-protected securities		3,291		16		—		3,307		—		3,291
Commercial paper		45,974		—		—		45,974				45,974		—
Subtotal		352,920		273		(128)		353,065		15,725		286,489		50,706
Total	$	652,816	$	401	$	(128)	$	653,089	$	155,443	$	406,667	$	90,706