Warrants (Detail)	9 Months Ended
	Sep. 30, 2018 $ / shares shares
Warrant Exercise Price Range One 4.50
Class of Warrant or Right [Line Items]
Warrants outstanding	5,000
Weighted average remaining contractual life	1 month 6 days
Warrants exercisable	5,000
Weighted average exercise price per share | $ / shares	$ 4.50
Warrant Exercise Price Range Two 9.00
Class of Warrant or Right [Line Items]
Warrants outstanding	1,092,350
Weighted average remaining contractual life	2 years 14 days
Warrants exercisable	1,092,350
Weighted average exercise price per share | $ / shares	$ 9.00
Warrant Exercise Price Range Three 10.00
Class of Warrant or Right [Line Items]
Warrants outstanding	1,433,916
Weighted average remaining contractual life	3 years 6 months 14 days
Warrants exercisable	1,433,916
Weighted average exercise price per share | $ / shares	$ 10.00
Warrant Exercise Price Range Four 11.00
Class of Warrant or Right [Line Items]
Warrants outstanding	837,362
Weighted average remaining contractual life	4 years 2 months 8 days
Warrants exercisable	837,362
Weighted average exercise price per share | $ / shares	$ 11.00
Warrant Exercise Price Range Five 4.50-11.00
Class of Warrant or Right [Line Items]
Warrants outstanding	3,368,628
Weighted average remaining contractual life	3 years 2 months 16 days
Warrants exercisable	3,368,628
Weighted average exercise price per share | $ / shares	$ 9.92