Fair Value Measurement (Tables)

12 Months Ended

Dec. 31, 2019

Fair Value Disclosures [Abstract]

Fair Value Measurements, Recurring and Nonrecurring

The following tables present the Company’s fair value hierarchy for those assets and liabilities measured at fair value as of December 31, 2019 and 2018 (in thousands):

	Total as of December 31, 2019		Level 1		Level 2		Level 3
Assets
Cash and cash equivalents:
Cash and money market funds	$	19,519	$	19,519	$	—	$	—
Investments:
U.S. government securities	32,175		32,175		—		—
Corporate securities	22,164		—		22,164		—
Commercial paper	14,922		—		14,922		—
Total investments	$	69,261	$	32,175	$	37,086	$	—
Liabilities
Warrant liabilities	$	150	$	—	$	—	$	150

	Total as of December 31, 2018		Level 1		Level 2		Level 3
Assets
Cash and cash equivalents:
Cash and money market funds	$	45,716	$	45,716	$	—	$	—
Investments:
U.S. government securities	38,737		38,737		—		—
Corporate securities	15,066		—		15,066		—
Agency securities	11,931		—		11,931		—
Commercial paper	1,183		1,183		—		—
Total investments	$	66,917	$	39,920	$	26,997	$	—
Liabilities
Warrant liabilities	$	860	$	—	$	—	$	860

Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation

The Company has determined that the warrant liabilities' fair values are Level 3 items within the fair value hierarchy. The following table presents the changes in the warrant liabilities (in thousands):

Balance at December 31, 2018	$	860
Exercise of warrants	(18		)
Change in fair value of warrants	(692		)
Balance at December 31, 2019	$	150