Other Current Assets- Additional Information (Detail) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Other Assets, Current	$ 1,163	$ 593
Prepaid Insurance		100
Acute Myeloid Leukemia [Member]
Other Assets, Current	1,100	400
Prepaid Expenses [Member]
Other Assets, Current	1,200	600
Other Prepaid Expenses [Member]
Other Assets, Current	$ 100	$ 100