Subsequent Events - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions							1 Months Ended	2 Months Ended	12 Months Ended
	Mar. 06, 2020	Mar. 04, 2020	Feb. 14, 2020	Nov. 27, 2019	May 08, 2019	Aug. 15, 2016	May 08, 2019	Mar. 04, 2020	Dec. 31, 2019	Dec. 31, 2018
Subsequent Event [Line Items]
Common stock warrants issued (in shares)										1
Consideration from sale of stock							$ 18.3
Subsequent Event
Subsequent Event [Line Items]
Proceeds from warrant exercises	$ 1.7
Private Investment in Public Equity (PIPE)
Subsequent Event [Line Items]
Proceeds from issuance of common stock and warrants						$ 7.5
Common stock warrants issued (in shares)						1
Payments for commissions on sale of stock						$ 0.9
Private Investment in Public Equity (PIPE) | Subsequent Event
Subsequent Event [Line Items]
Warrants to purchase common stock (in shares)		11,903,506						11,903,506
Proceeds from issuance of common stock and warrants		$ 10.2
Shares issued in transaction (in shares)		11,903,506
Exercise price (in USD per share)		$ 0.9275						$ 0.9275
Underwriting Agreement
Subsequent Event [Line Items]
Shares issued in transaction (in shares)					750,000
Price of stock sold (in USD per share)					$ 3.29		$ 3.29
Underwriting Agreement | Subsequent Event
Subsequent Event [Line Items]
Warrants to purchase common stock (in shares)	2,633,500
Exercise price (in USD per share)	$ 0.65
Period for additional purchase of stock			30 days
Consideration from sale of stock			$ 8.3
Underwriting Agreement | Common Class A | Subsequent Event
Subsequent Event [Line Items]
Shares issued in transaction (in shares)			10,146,154
Number of share of common stock Included in the issued combination (in shares)			1
Price of stock sold (in USD per share)			$ 0.65
Underwriting Agreement | Common Class B | Subsequent Event
Subsequent Event [Line Items]
Shares issued in transaction (in shares)			2,161,539
Price of stock sold (in USD per share)			$ 0.6499
Exercise price (in USD per share)			$ 0.65
Warrants expiration term			5 years
Underwriting Agreement | Common Class C | Subsequent Event
Subsequent Event [Line Items]
Shares issued in transaction (in shares)			1,846,153
At-The-Market Offering
Subsequent Event [Line Items]
Shares issued in transaction (in shares)									3,599,141
Price of stock sold (in USD per share)									$ 1.57
Consideration from sale of stock									$ 5.2
Payments for commissions on sale of stock									$ 0.2
At-The-Market Offering | Subsequent Event
Subsequent Event [Line Items]
Consideration from sale of stock								$ 2.7
Payments for commissions on sale of stock								$ 0.1
Common Stock
Subsequent Event [Line Items]
Price of stock sold (in USD per share)				$ 1.45
Consideration from sale of stock				$ 3.1
Common Stock | At-The-Market Offering | Subsequent Event
Subsequent Event [Line Items]
Shares issued in transaction (in shares)								2,151,346
Price of stock sold (in USD per share)		$ 1.30						$ 1.30
Series C Warrant | Underwriting Agreement | Common Class A | Subsequent Event
Subsequent Event [Line Items]
Number of share of warrants included in the issued combination (in shares)			1
Common stock warrants issued (in shares)			1
Series C Warrant | Underwriting Agreement | Common Class B | Subsequent Event
Subsequent Event [Line Items]
Number of share of warrants included in the issued combination (in shares)			1
Common stock warrants issued (in shares)			1
Series D Pre Funded Warrant | Underwriting Agreement | Common Class B | Subsequent Event
Subsequent Event [Line Items]
Number of share of common stock Included in the issued combination (in shares)			1
Number of share of warrants included in the issued combination (in shares)			1