Stock Incentive Plans - Intrinsic Value Calculated Based on Grant Date Fair Value (Detail) - $ / shares	1 Months Ended	4 Months Ended		5 Months Ended	12 Months Ended
	Sep. 30, 2016	Apr. 30, 2016	Jul. 31, 2015	Jul. 31, 2015	Dec. 31, 2016	Dec. 31, 2015
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Number of options granted	892,500	51,120	900,084	92,600	943,620	992,684
Intrinsic value calculated based on grant date fair value, Exercise price		$ 0.73	$ 1.00	$ 2.43
Intrinsic value calculated based on grant date fair value, Exercise price	$ 0.61	1.14	1.35	4.04
Intrinsic value calculated based on grant date fair value, Intrinsic value per share