Fair Value Measurements (Tables)

12 Months Ended

Dec. 31, 2019

Fair Value Disclosures [Abstract]

Summary of Financial Assets and Liabilities Measured at Fair Value on a Recurring Basis

The following tables set forth the fair value of financial assets and liabilities as of December 31, 2019 and 2018 that were measured at fair value on a recurring basis (in thousands):

	December 31, 2019
	Level 1		Level 2		Level 3		Total
Financial assets
Money market funds	$	88,683	$	—	$	—	$	88,683
Commercial paper		—		121,867		—		121,867
U.S. government debt and agency securities		—		377,243		—		377,243
Corporate bonds		—		86,615		—		86,615
Total financial assets	$	88,683	$	585,725	$	—	$	674,408

	December 31, 2018
	Level 1		Level 2		Level 3		Total
Financial assets
Money market funds	$	45,998	$	—	$	—	$	45,998
Commercial paper		—		16,887		—		16,887
U.S. government debt and agency securities		—		85,623		—		85,623
Corporate bonds		—		7,478		—		7,478
Total financial assets	$	45,998	$	109,988	$	—	$	155,986
Financial liabilities
Convertible preferred stock warrant liability	$	—	$	—	$	336	$	336
Total financial liabilities	$	—	$	—	$	336	$	336

Summary of Fair Value of Convertible Preferred Stock Warrant Liability Estimated Using Black-Scholes Option Pricing Model

As of December 31, 2018, the fair value of the convertible preferred stock warrant liability was estimated using the Black-Scholes option-pricing model with the following inputs:

	December 31, 2018
Fair value estimate	$	8.27
Expected term (in years)		2.31
Risk-free interest rate		2.5	%
Expected volatility		55.3	%
Expected dividend yield		—