Fair Value Measurement (Tables)

12 Months Ended

Dec. 31, 2019

Fair Value Disclosures [Abstract]

Schedule of Assets and Liabilities Measured at Fair Value On A Recurring Basis

Assets and liabilities measured at fair value on a recurring basis consist of the following as of December 31, 2019 (in thousands):

			Fair Value Measurements at Reporting Date Using
	December 31, 2019		Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
Assets:
Money market funds	$	30,693	$	30,693	$	—	$	—
Marketable securities:
Corporate debt securities	42,709		—		42,709		—
Tax-exempt municipal securities	23,198		—		23,198		—
Variable rate demand notes	5,600		—		5,600		—
Total assets at fair value on a recurring basis	$	102,200	$	30,693	$	71,507	$	—
Liabilities:
Deferred payments	$	3,257	$	—	$	—	$	3,257

Assets and liabilities measured at fair value on a recurring basis consist of the following as of December 31, 2018 (in thousands):

			Fair Value Measurements at Reporting Date Using
	December 31, 2018		Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
Assets:
Money market funds	$	1,791	$	1,791	$	—	$	—
Marketable securities:
Corporate debt securities	48,430		—		48,430		—
Tax-exempt municipal securities	22,869		—		22,869		—
Variable rate demand notes	4,000		—		4,000		—
Total assets at fair value on a recurring basis	$	77,090	$	1,791	$	75,299	$	—
Liabilities:
Deferred payments	$	4,120	$	—	$	—	$	4,120

Schedule of Changes in Fair Value of Level 3 Liability

Changes in the fair value of the Company’s Level 3 liabilities during the years ended December 31, 2018 and 2019 are as follows (in thousands):

	December 31, 2018			December 31, 2019
Balance as of the beginning of period	$	4,514		$	4,120
Amounts paid	(1,412		)	(1,579		)
Other adjustments to fair value	1,018			716
Balance at end of period	$	4,120		$	3,257