Warrants - Summary of Common Stock Warrants Outstanding (Detail) - $ / shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Mar. 09, 2017	Dec. 31, 2016
Class Of Warrant Or Right [Line Items]
Number of Common Stock Warrants	7,344,297	78,336		20,404
Per Share Exercise Price	$ 5.03		$ 0.01
Replacement Warrants Issued in Connection With Mergers [Member]
Class Of Warrant Or Right [Line Items]
Number of Common Stock Warrants	155	155
Per Share Exercise Price	$ 483.00	$ 483.00
Issuance Date	Mar. 03, 2012	Mar. 03, 2012
Expiration Date	Mar. 03, 2022	Mar. 03, 2022
Warrants Issued with Redeemable Preferred [Member]
Class Of Warrant Or Right [Line Items]
Number of Common Stock Warrants	1,612	78,181
Per Share Exercise Price	$ 80.10	$ 80.10
Issuance Date	Aug. 16, 2017	Aug. 16, 2017
Expiration Date	Aug. 16, 2022	Aug. 16, 2022
Warrants Issued with Common Units in Unit Offering [Member]
Class Of Warrant Or Right [Line Items]
Number of Common Stock Warrants	2,516,250
Per Share Exercise Price	$ 4.18
Issuance Date	Oct. 02, 2018
Expiration Date	Oct. 02, 2023
Underwriter Warrant Issued with Public Offering [Member]
Class Of Warrant Or Right [Line Items]
Number of Common Stock Warrants	196,650
Per Share Exercise Price	$ 6.25
Issuance Date	Oct. 02, 2018
Expiration Date	Sep. 28, 2021
Issued with Common Units in Registered Direct Offering [Member]
Class Of Warrant Or Right [Line Items]
Number of Common Stock Warrants	4,629,630
Per Share Exercise Price	$ 5.40
Issuance Date	Oct. 10, 2018
Expiration Date	Oct. 10, 2023