Fair Value Measurements (Tables)

12 Months Ended

Dec. 31, 2019

Assets Measured at Fair Value on Recurring Basis

The following table presents the hierarchy for assets measured at fair value on a recurring basis as of December 31, 2019 and December 31, 2018 (in thousands):

	Fair Value Measurements at End of Period Using:
			Quoted Market		Significant		Significant
			Prices for		Other Observable		Unobservable
	Total		Identical Assets		Inputs		Inputs
	Fair Value		(Level 1)		(Level 2)		(Level 3)
As of December 31, 2019
Money market funds	$	82,125	$	82,125	$	—	$	—
U.S. Treasury and agency securities		91,717		91,717		—		—
Commercial paper		37,411		—		37,411		—
Corporate debt securities		156,277		—		156,277		—
As of December 31, 2018
Money market funds	$	17,295	$	17,295	$	—	$	—
U.S. Treasury securities		123,439		123,439		—		—

Schedule of Available for Sale Investments by Security Type

The aggregate market value, cost basis, and gross unrealized gains and losses of available-for-sale investments by security type, classified in marketable securities and long-term investments as of December 31, 2019 are as follows (in thousands):

			Gross		Gross
	Amortized		Unrealized		Unrealized			Total
	Cost		Gains		Losses			Fair Value
Marketable securities
U.S. Treasury and agency securities	$	77,993	$	57	$	—		$	78,050
Commercial paper		32,413		—		—			32,413
Corporate debt securities		156,059		238		(20	)		156,277
Total marketable securities	$	266,465	$	295	$	(20	)	$	266,740

Schedule of Contractual Maturities of Available-for-sale Debt Securities

Contractual maturities of available-for-sale debt securities, as of December 31, 2019, were as follows (in thousands):

	Estimated
	Fair Value
Due within one year	$	237,449
One to two years		29,291
Total	$	266,740