Warrants - Schedule of Key Terms of Placement Warrants (Detail) - $ / shares	1 Months Ended		3 Months Ended
	Jan. 31, 2017	Sep. 30, 2016	Mar. 31, 2019
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Warrants Exercised			21,571
Warrants Outstanding			2,818,576
2017 Placement Warrants
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Issuance Date			2017-01
Term	7 years
Exercise Price Per Share	$ 3.17		$ 3.17
Warrants Exercised			6,022
Warrants Outstanding			1,703,510
2016 Placement Warrants
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Issuance Date			2016-08
Issuance Date			2016-09
Term		7 years	7 years
Exercise Price Per Share		$ 2.95	$ 2.95
Warrants Exercised			15,549
Warrants Outstanding			1,115,066