Warrants - Summary of Warrants Outstanding (Detail) - $ / shares	9 Months Ended
	Sep. 30, 2018	Apr. 06, 2018	Dec. 31, 2017	Dec. 31, 2016
Class of Warrant or Right [Line Items]
Exercise Price		$ 2.00
Warrants Outstanding	16,877,425		2,177,425	17,559
Class One [Member]
Class of Warrant or Right [Line Items]
Exercise Price	$ 3.10
Warrants Outstanding	48,387
Expiration Date	Sep. 19, 2022
Class Two [Member]
Class of Warrant or Right [Line Items]
Exercise Price	$ 3.10
Warrants Outstanding	462,106
Expiration Date	May 10, 2024
Class Three [Member]
Class of Warrant or Right [Line Items]
Exercise Price	$ 3.10
Warrants Outstanding	602,414
Expiration Date	Jul. 25, 2024
Class Four [Member]
Class of Warrant or Right [Line Items]
Exercise Price	$ 3.10
Warrants Outstanding	1,064,518
Expiration Date	Nov. 08, 2024
Class Five [Member]
Class of Warrant or Right [Line Items]
Exercise Price	$ 2.00
Warrants Outstanding	900,000
Expiration Date	Apr. 10, 2023
Class Six [Member]
Class of Warrant or Right [Line Items]
Exercise Price	$ 1.00
Warrants Outstanding	13,800,000
Expiration Date	Jul. 17, 2025