Stock-Based Compensation - Summary of Stock Option and Award Activity Excluding Inducement Grants (Detail) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Shares Available for Grant
Beginning balance (in shares)	55,799.000	29,571
Additional shares reserved (in shares)	419,056	1,225,223
Options granted (in shares)	(503,950)	(1,212,200)
Options canceled/forfeited/expired (in shares)	93,914	15,072
Ending balance (in shares)	63,404	55,799.000	29,571
Outstanding Number of Shares
Beginning balance (in shares)	1,296,157	99,029
Options granted (in shares)	503,950	1,212,200
Options canceled/forfeited/expired (in shares)	(93,914)	(15,072)
Shares expired under 2012 Plan (in shares)		0
Ending balance (in shares)	1,706,193	1,296,157	99,029
Exercisable (in shares)	571,852
Weighted- Average Exercise Price per Share
Beginning balance (in USD shares)	$ 5.75	$ 25.33
Options granted (in USD shares)	3.27	4.24
Options cancelled/forfeited/expired (in USD shares)	6.03	12.38
Shares expired under 2012 Plan (in USD shares)		0.00
Ending balance (in USD shares)	5.00	$ 5.75	$ 25.33
Exercisable (in USD shares)	$ 6.86
Weighted- Average Remaining Contractual Term (In Years)
Average Remaining Contractual Term	7 years 7 months 2 days	9 years 2 months 23 days	8 years 5 months 16 days
Exercisable	7 years 4 months 28 days
Aggregate Intrinsic Value
Vested or expected to vest	$ 0.0	$ 0.0
Exercisable	$ 0.0
2012 Stock Incentive Plan
Shares Available for Grant
Shares expired under 2012 Plan (in shares)	(1,415)	(1,867)