Schedule of Common Stock on Warrants Exercised (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Class Of Warrant Or Right [Line Items]
Class of warrants exercised during period | shares	2,559,217
Proceeds from the exercise of warrants	$ 12,298,378	$ 10,166,000
Series A
Class Of Warrant Or Right [Line Items]
Class of warrants exercised during period | shares	83,333
Proceeds from the exercise of warrants	$ 500,000
Series D
Class Of Warrant Or Right [Line Items]
Class of warrants exercised during period | shares	501,570
Proceeds from the exercise of warrants	$ 1,315,694
Series E
Class Of Warrant Or Right [Line Items]
Class of warrants exercised during period | shares	326,450
Proceeds from the exercise of warrants	$ 65,290
Series F
Class Of Warrant Or Right [Line Items]
Class of warrants exercised during period | shares	233,857
Proceeds from the exercise of warrants	$ 1,403,143
Series G
Class Of Warrant Or Right [Line Items]
Class of warrants exercised during period | shares	328,571
Proceeds from the exercise of warrants	$ 65,714
Series H
Class Of Warrant Or Right [Line Items]
Class of warrants exercised during period | shares	900,436
Proceeds from the exercise of warrants	$ 8,911,537
Series J
Class Of Warrant Or Right [Line Items]
Class of warrants exercised during period | shares	185,000
Proceeds from the exercise of warrants	$ 37,000