Cash Equivalents and Marketable Securities

12 Months Ended

Dec. 31, 2019

Investments, Debt and Equity Securities [Abstract]

Cash Equivalents and Marketable Securities

At December 31, 2019, marketable securities consisted of the following (in thousands):


	Amortized Cost		Unrealized Gains		Unrealized Losses		Aggregate Fair Value
Money market funds	$	360,471	$	—	$	—	$	360,471

U.S. treasury debt securities	10,342		8		(1)		10,349
U.S. corporate debt securities	95,706		164		(5)		95,865
	$	466,519	$	172	$	(6)	$	466,685
Included in cash and cash equivalents	$	360,471	$	—	$	—	$	360,471
Included in marketable securities	$	106,048	$	172	$	(6)	$	106,214

At December 31, 2018, marketable securities consisted of the following (in thousands):


	Amortized Cost		Unrealized Gains		Unrealized Losses		Aggregate Fair Value
Money market funds	$	52,068	$	—	$	—	$	52,068
Commercial paper	7,448		—		—		7,448
U.S. treasury debt securities	2,494		—		(1)		2,493
U.S. corporate debt securities	10,890		—		(67)		10,823
	$	72,900	$	—	$	(68)	$	72,832
Included in cash and cash equivalents	$	52,068	$	—	$	—	$	52,068
Included in marketable securities	$	20,832	$	—	$	(68)	$	20,764

The following table presents gross unrealized losses and fair values for those marketable securities that were in an unrealized loss position as of December 31, 2019, aggregated by investment category and the length of time that individual securities have been in a continuous loss position (in thousands):


	As of December 31, 2019
	Less than 12 months						12 months or greater
	Fair Value		Unrealized Loss		Fair Value		Unrealized Loss
U.S. treasury debt securities	$	2,020	$	(1)	$	—	$	—
U.S. corporate debt securities	7,065		(4)		2,000		(1)
Total	$	9,085	$	(5)	$	2,000	$	(1)

We do not believe any of the unrealized losses represented an other-than-temporary impairment based on our evaluation of available evidence, which includes our intent as of December 31, 2019 to hold these investments until the cost basis is recovered.