Warrants (Detail) - $ / shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Class of Warrant or Right [Line Items]
Weighted average remaining contractual life		5 years
Warrant Exercise Price Range One 9.00
Class of Warrant or Right [Line Items]
Warrants outstanding	1,079,622
Weighted average remaining contractual life	1 year 9 months 14 days
Warrants exercisable	1,079,622
Weighted average exercise price per share	$ 9.00
Warrant Exercise Price Range Two 10.00
Class of Warrant or Right [Line Items]
Warrants outstanding	1,421,508
Weighted average remaining contractual life	3 years 3 months 14 days
Warrants exercisable	1,421,508
Weighted average exercise price per share	$ 10.00
Warrant Exercise Price Range Three 11.00
Class of Warrant or Right [Line Items]
Warrants outstanding	830,865
Weighted average remaining contractual life	3 years 11 months 8 days
Warrants exercisable	830,865
Weighted average exercise price per share	$ 11.00
Warrant Exercise Price Range Four 9.00 - 10.00
Class of Warrant or Right [Line Items]
Warrants outstanding	3,331,995
Weighted average remaining contractual life	2 years 11 months 19 days
Warrants exercisable	3,331,995
Weighted average exercise price per share	$ 9.92