Other Current Assets- Additional Information (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Other Assets Current	$ 353	$ 902
Prepaid Insurance	100
Chronic Myelogenous Lleukemia [Member]
Other Assets Current	200
Prepaid Expenses [Member]
Other Assets Current	400	$ 900
Other Prepaid Expenses [Member]
Other Assets Current	$ 100