Stock-Based Compensation - Summary of Option and RSU Activity (Detail) - Equity Incentive Plan 2019 - $ / shares	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Shares Available for Grant
Balance at the beginning of the year (in shares)	88,000	200,000
Options granted (in shares)		(145,000)
Options cancelled and returned to Plan (in shares)		1,000
Plan termination (in shares)		(32,000)
Balance at the end of the period (in shares)	81,000	88,000
Number of Shares
Balance at the beginning of the year (in shares)	161,000	17,000
Options granted (in shares)		145,000
Options cancelled and returned to Plan (in shares)	(2,000)	(1,000)
Balance at the end of the period (in shares)	159,000	161,000
Weighted Average Exercise Prices
Weighted-average exercise price (in dollars per share)	$ 10.85	$ 96.24
Options granted (in dollars per share)		2.64
Options cancelled and returned to Plan (in dollars per share)	4.00	144.00
Weighted-average exercise price (in dollars per share)	$ 10.82	$ 10.85
Options
Shares Available for Grant
Additional shares authorized under the Plan		183,000
RSU's
Shares Available for Grant
RSUs granted (in shares)	(9,000)	(120,000)
RSUs cancelled and returned to Plan (in shares)	2,000	1,000
Number of Shares
RSUs cancelled and returned to Plan (in shares)	2,000	1,000
Weighted Average Exercise Prices
RSUs granted (in dollars per share)	$ 1.74	$ 3.79
RSUs cancelled and returned to Plan (in dollars per shares)	$ 4.00	$ 25.13