Net Income (Loss) Per Common Share - Additional Information (Detail) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Earnings Per Share [Abstract]
Amounts allocated to participating securities	$ 0	$ 0	$ 0	$ 0
Participating securities outstanding, shares	0	0	0	0