Summary of Warrant (Detail)	12 Months Ended
	Dec. 31, 2017 USD ($) $ / shares shares
Shares [Abstract]
Number of warrants, Outstanding | shares
Number Of Warrants Assumed From Merger | shares	1,898,541
Number Of Warrants Granted | shares	1,750,000
Number Of Warrants Exercised | shares	0
Class Of Warrant Or Right Cancelled In Period | shares	0
Number of warrants, Outstanding | shares	3,648,541
Weighted Average Exercise Price [Abstract]
Class Of Warrants Or Right, Exercise Price Of Warrants Assumed From Merger | $ / shares	$ 9.06
Class Of Warrants Or Right, Exercise Price Of Warrants Grant In Period | $ / shares	10.49
Class Of Warrants Or Right, Exercise Price Of Warrants Exercised In Period | $ / shares	0
Class Of Warrants Or Right, Exercise Price Of Warrants Forfeited In Period | $ / shares	0
Class of Warrant or Right, Exercise Price of Warrants or Rights | $ / shares	$ 9.75
Weighted Average Remaining Contractual Term Years [Abstract]
Class Of Warrant Or Rights Assumed From Merger Weighted Average Remaining Contractual Term	2 years 8 months 8 days
Class Of Warrant Or Rights Grant In Period Weighted Average Remaining Contractual Term	5 years
Class Of Warrant Or Rights Exercised Weighted Average Remaining Contractual Term	0 years
Class Of Warrant Or Rights Forfeited Weighted Average Remaining Contractual Term	0 years
Class Of Warrant Or Rights Outstanding Weighted Average Remaining Contractual Term	3 years 8 months 26 days
Aggregate Intrinsic Value [Abstract]
Class Of Warrants Or Right, Outstanding, Aggregate Intrinsic Value | $
Class Of Warrants Or Right, Assumed From Merger, Aggregate Intrinsic Value | $	14.94
Class Of Warrants Or Right, Grant In Period, Aggregate Intrinsic Value | $	13.51
Class Of Warrants Or Right, Exercises In Period, Aggregate Intrinsic Value | $	0
Class Of Warrants Or Right, Forfeitures In Period, Aggregate Intrinsic Value | $	0
Class Of Warrants Or Right, Outstanding, Aggregate Intrinsic Value | $	$ 14.25