Property and Equipment - Summary of Property and Equipment (Detail) $ in Thousands	Dec. 31, 2017 USD ($)
Property, Plant and Equipment [Line Items]
Cost	$ 1,144
Accumulated Depreciation	1,085
Net Book Value	59
Computer equipment [Member]
Property, Plant and Equipment [Line Items]
Cost	389
Accumulated Depreciation	358
Net Book Value	31
Furniture and fixtures [Member]
Property, Plant and Equipment [Line Items]
Cost	157
Accumulated Depreciation	156
Net Book Value	1
Leasehold improvements [Member]
Property, Plant and Equipment [Line Items]
Cost	252
Accumulated Depreciation	226
Net Book Value	26
Computer software [Member]
Property, Plant and Equipment [Line Items]
Cost	322
Accumulated Depreciation	321
Net Book Value	1
Equipment under capital lease [Member]
Property, Plant and Equipment [Line Items]
Cost	24
Accumulated Depreciation	$ 24