Commitments and Contingencies - Lease Expense (Detail) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Commitments and Contingencies Disclosure [Abstract]
Balance as of December 31, 2019			$ 1,003,000
Amortization			(88,000)
Balance as of June 30, 2020	$ 915,000		915,000
Lease expense	$ 66,000	$ 65,000	$ 132,000	$ 131,000