Financial Instruments

6 Months Ended

Jun. 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 June 30, 2020 and as of December 31, 2019 are presented in the following tables:


	June 30, 2020
	Amortized Cost		Unrealized Gains		Unrealized Losses		Fair Value
	(in thousands)
Money market funds	$	256,773	$	—	$	—	$	256,773
Commercial paper	79,822		90		(2)		79,910
Corporate bonds	290,898		1,205		(48)		292,055
U.S. treasury securities	422,592		907		(13)		423,486
U.S. agency securities	34,479		137		(2)		34,614
Total cash equivalents and investments	$	1,084,564	$	2,339	$	(65)	$	1,086,838

Classified as:
Cash equivalents							$	256,773
Short-term investments							619,271
Long-term investments							210,794
Total cash equivalents and investments							$	1,086,838


	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 June 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 June 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.