Fair Value of Financial Instruments (Tables)

9 Months Ended

12 Months Ended

Sep. 30, 2019

Dec. 31, 2018

Fair Value of Financial Instruments

Summary of fair value of the Company's financial assets

The following tables set forth the fair value of the Company’s financial assets by level within the fair value hierarchy (in thousands):

	September 30, 2019
	Carrying
	Amount		Fair Value		Level 1		Level 2		Level 3
Cash equivalents:
Money market	$	5,465	$	5,465	$	5,465	$	—	$	—
Marketable securities:
U.S. treasury securities		19,982		19,983		—		19,983		—
Agency bonds		47,178		47,161		—		47,161		—
Corporate bonds		107,045		107,003		—		107,003		—
Total	$	179,670	$	179,612	$	5,465	$	174,147	$	—

	December 31, 2018
	Carrying
	Amount		Fair Value		Level 1		Level 2		Level 3
Cash equivalents:
Money market	$	5,000	$	5,000	$	5,000		—		—

The following table sets forth the fair value of the Company’s financial assets by level within the fair value hierarchy (in thousands):

	As of December 31, 2018
					Fair Value Measurement Based on
							Significant
					Quoted Prices in		Other		Significant
	Carrying		Fair		Active Markets		Observable		Unobservable
Assets	Amount		Value		(Level 1)		Inputs (Level 2)		Inputs (Level 3)
Money market funds (cash equivalents)	$	5,000	$	5,000	$	5,000	$	—	$	—

	As of December 31, 2017
					Fair Value Measurement Based on
							Significant
					Quoted Prices in		Other		Significant
	Carrying		Fair		Active Markets		Observable		Unobservable
Assets	Amount		Value		(Level 1)		Inputs (Level 2)		Inputs (Level 3)
Money market funds (cash equivalents)	$	1,000	$	1,000	$	1,000	$	—	$	—