Financial Instruments

9 Months Ended

Sep. 30, 2020

Investments, All Other Investments [Abstract]

The fair value and amortized cost of cash equivalents and available-for-sale securities by major security type as of September 30, 2020 and as of December 31, 2019 are presented in the following tables:


	September 30, 2020
	Amortized Cost		Unrealized Gains		Unrealized Losses		Fair Value
	(in thousands)
Money market funds	$	101,013	$	—	$	—	$	101,013
Commercial paper	73,938		30		—		73,968
Corporate bonds	284,902		784		(29)		285,657
U.S. treasury securities	468,178		561		(14)		468,725
U.S. agency securities	62,517		69		(5)		62,581
Total cash equivalents and investments	$	990,548	$	1,444	$	(48)	$	991,944

Classified as:
Cash equivalents							$	101,065
Short-term investments							682,886
Long-term investments							207,993
Total cash equivalents and investments							$	991,944


	December 31, 2019
	Amortized Cost		Unrealized Gains		Unrealized Losses		Fair Value
	(in thousands)
Money market funds	$	122,900	$	—	$	—	$	122,900
Corporate bonds	204,144		871		(4)		205,011
U.S. treasury securities	181,340		557		(3)		181,894
U.S. agency securities	25,658		167		(1)		25,824
Certificates of deposit	1,000		—		—		1,000
Total cash equivalents and investments	$	535,042	$	1,595	$	(8)	$	536,629

Classified as:
Cash equivalents							$	122,900
Short-term investments							355,407
Long-term investments							58,322
Total cash equivalents and investments							$	536,629

As of September 30, 2020, the remaining contractual maturities of available-for-sale securities were less than 3 years. There have been no significant realized losses on available-for-sale securities for the periods presented. As of September 30, 2020, unrealized losses on available-for-sale investments are not attributed to credit risk. The Company believes that it is more-likely-than-not that investments in an unrealized loss position will be held until maturity and all interest and principal will be received. The Company believes that an allowance for credit losses is unnecessary because the unrealized losses on certain of the Company’s marketable securities are due to market factors. To date, the Company has not recorded any impairment charges on marketable securities.