Property and Equipment - Schedule of Property and Equipment (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Property, Plant and Equipment [Line Items]
Property and equipment, cost	$ 1,440	$ 1,024
Property and equipment, accumulated amortization	535	175
Property and equipment, net book Value	905	849
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, cost	715	490
Property and equipment, accumulated amortization	259	77
Property and equipment, net book Value	456	413
Office Furniture, Equipment and Systems [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, cost	725	534
Property and equipment, accumulated amortization	276	98
Property and equipment, net book Value	$ 449	$ 436