Fair Value of Financial Instruments - Summary of Changes in Fair Value of Level 3 Financial Instruments (Detail) $ in Thousands	9 Months Ended
	Sep. 30, 2020 USD ($) shares
Purchase price contingent liability [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at the beginning of period	$ 5,938
Change in value of liabilities	4,200
Balance at end of period	$ 10,138
Series C Warrant [Member] | Common stock warrant liability [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at the beginning of period, in shares | shares	118,083
Expiration of warrants, in shares | shares	(118,083)
2017 PIPE Warrant Liability [Member] | Common stock warrant liability [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at the beginning of period	$ 10,822
Balance at the beginning of period, in shares | shares	6,024,425
Change in value of liabilities	$ (6,045)
Balance at end of period	$ 4,777
Balance at the end of period, in shares | shares	6,024,425
2018 PIPE Warrant Liability [Member] | Common stock warrant liability [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at the beginning of period	$ 1,354
Balance at the beginning of period, in shares | shares	513,617
Change in value of liabilities	$ (487)
Balance at end of period	$ 867
Balance at the end of period, in shares | shares	513,617