Stock Options and Restricted Stock - Summary of Activity for Unvested Options Outstanding (Detail) - $ / shares	3 Months Ended	12 Months Ended
	Jun. 30, 2018	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award, Options, Nonvested, Number of Shares [Roll Forward]
Number of options beginning balance	46,666
Number of options, granted	24,000	29,666
Number of options, cancelled	0
Number of options, vested	(17,000)
Number of options ending balance	53,666
Exercise price per share beginning balance, Lower limit	$ 2.14
Exercise price per share beginning balance, Upper limit	9.38
Exercise price per share, Granted	5.58
Exercise price per share, Cancelled	0
Exercise price per share, Vested, lower limit	2.22
Exercise price per share, Vested, upper limit	9.38
Exercise price per share ending balance, Lower limit	2.14
Exercise price per share ending balance, Upper limit	7.1
Weighted average exercise price	4.52
Weighted average exercise price, granted	5.58
Weighted average exercise price, cancelled	0
Weighted average exercise price, vested	7.16
Weighted average exercise price	$ 4.16