Accrued Payroll and Employee Benefits - Components of Accrued Payroll and Employee Benefits (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Payables and Accruals [Abstract]
Accrued payroll	$ 808	$ 1,075
Accrued benefits	408	1,613
Accrued severance	285	1,440	$ 4,148
Total accrued payroll and employee benefits	1,501	$ 4,128
Officers' compensation	1,000
Accrued vacation, decrease from revision	$ 1,100