Stock-Based Compensation - Summary of Company's Inducement Grant Stock Option Activities (Detail) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
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)
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
Ending balance (in USD shares)	5.00	$ 5.75	$ 25.33
Exercisable (in USD shares)	$ 6.86
Weighted- Average Remaining Contractual Term (In Years)
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
Inducement Grant
Outstanding Number of Shares
Beginning balance (in shares)	13,837	19,350
Options granted (in shares)	550,000	0
Options canceled/forfeited/expired (in shares)	(9,723)	(5,513)
Ending balance (in shares)	554,114	13,837	19,350
Exercisable (in shares)	3,228
Weighted- Average Exercise Price per Share
Beginning balance (in USD shares)	$ 20.60	$ 19.12
Options granted (in USD shares)	1.89	0.00
Options cancelled/forfeited/expired (in USD shares)	17.81	15.40
Ending balance (in USD shares)	2.08	$ 20.60	$ 19.12
Exercisable (in USD shares)	$ 27.20
Weighted- Average Remaining Contractual Term (In Years)
Remaining Contractual Term	9 years 9 months 4 days	4 years 6 months 7 days	8 years 10 months 28 days
Exercisable	3 years 9 months 7 days
Aggregate Intrinsic Value
Vested or expected to vest	$ 0.0	$ 0.0
Exercisable	$ 0.0