Earnings Per share - Additional Information (Detail) - shares	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Employee Stock Option [Member]
Earnings Per Share Basic And Diluted [Line Items]
Antidilutive securities excluded from calculation of earnings per share	4,157,559	2,370,106	2,354,244	2,370,106
Warrant [Member]
Earnings Per Share Basic And Diluted [Line Items]
Antidilutive securities excluded from calculation of earnings per share	596,000	596,000	596,000	596,000
Restricted Stock Units (RSUs) [Member]
Earnings Per Share Basic And Diluted [Line Items]
Antidilutive securities excluded from calculation of earnings per share	191,033	0	0	0