Investments

12 Months Ended

Dec. 31, 2021

Investments [Abstract]

Investments

4. Investments

The Company invests portions of excess cash in United States treasuries, commercial paper, non-U.S. government securities, municipal securities, and corporate debt securities with maturities ranging from three to eighteen months from the purchase date. These investments are accounted for as available-for-sale securities and are classified as short-term and long-term investments in the accompanying consolidated balance sheets based on each security’s contractual maturity date.

The following table summarizes the Company’s investments accounted for as available-for-sale securities as of December 31, 2021 and 2020 (in thousands):

	Maturity (in years)	Amortized Cost		Unrealized Losses			Unrealized Gains		Estimated Fair Value
December 31, 2021
Classified as current assets:
U.S. Treasury debt securities	1 or less	$	70,653	$	(163	)	$	—	$	70,490
Municipal securities	1 or less		18,017		(6	)		1		18,012
Corporate debt securities	1 or less		169,736		(187	)		—		169,549
Commercial paper	1 or less		224,333		(59	)		2		224,276
Total short-term investments		$	482,739	$	(415	)	$	3	$	482,327
Classified as non-current assets:
U.S. Treasury debt securities	Greater than 1	$	9,989	$	(35	)	$	—	$	9,954
Municipal securities	Greater than 1		9,034		(42	)		—		8,992
Corporate debt securities	Greater than 1		81,989		(271	)		—		81,718
Total long-term investments		$	101,012	$	(348	)	$	—	$	100,664
December 31, 2020
Classified as current assets:
U.S. Treasury debt securities	1 or less	$	39,736	$	—		$	31	$	39,767
Non-U.S. government securities	1 or less		5,054		—			2	$	5,056
Municipal securities	1 or less		3,082		(1	)		—	$	3,081
Corporate debt securities	1 or less		159,947		(68	)		124	$	160,003
Commercial paper	1 or less		107,680		(18	)		—	$	107,662
Total short-term investments		$	315,499	$	(87	)	$	157	$	315,569

As of December 31, 2021 and 2020, the Company had $1.1 million and $1.5 million, respectively, of accrued interest on investments recorded in prepaid expenses and other assets on the consolidated balance sheets.

The following tables present gross unrealized losses and fair values for those investments that were in an unrealized loss position as of December 31, 2021 and December 31, 2020, aggregated by investment category and the length of time that individual securities have been in a continuous loss position (in thousands):

	Less Than 12 Months					12 Months or Greater				Total
	Estimated Fair Value		Unrealized Losses			Estimated Fair Value		Unrealized Losses		Estimated Fair Value		Unrealized Losses
December 31, 2021
U.S. Treasury debt securities	$	80,444	$	(198	)	$	—	$	—	$	80,444	$	(198	)
Municipal securities		23,352		(48	)		—		—		23,352		(48	)
Corporate debt securities		250,467		(458	)		—		—		250,467		(458	)
Commercial paper		59,863		(59	)		—		—		59,863		(59	)
Total	$	414,126	$	(763	)	$	—	$	—	$	414,126	$	(763	)
December 31, 2020
Municipal securities	$	3,081	$	(1	)	$	—	$	—	$	3,081	$	(1	)
Corporate debt securities		108,147		(68	)		—		—		108,147		(68	)
Commercial paper		55,688		(18	)		—		—		55,688		(18	)
Total	$	166,916	$	(87	)	$	—	$	—	$	166,916	$	(87	)

The Company reviews its investment holdings at the end of each reporting period and evaluates any unrealized losses using the expected credit loss model to determine if the unrealized loss is a result of a credit loss or other factors. The Company also evaluates its investment holdings for impairment using a variety of factors including the Company’s intent to sell the underlying securities prior to maturity and whether it is more likely than not that the Company would be required to sell the securities before the recovery of their amortized basis. During the years ended December 31, 2021, 2020 and 2019, the Company did not recognize any impairment or realized gains or losses on sales of investments, and the Company did not record an allowance for, or recognize, any expected credit losses.