Fixed assets - Summary of Equipment and Leasehold Improvements (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Property, Plant and Equipment [Line Items]
Equipment and leasehold improvements, gross	$ 628	$ 628
Less: accumulated depreciation and amortization	616	603
Equipment and leasehold improvements, net	12	25
Equipment [Member]
Property, Plant and Equipment [Line Items]
Equipment and leasehold improvements, gross	$ 601	601
Equipment [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Equipment, useful lives in years	3 years
Equipment [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Equipment, useful lives in years	7 years
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Leasehold improvements, useful lives in years	Term of lease
Equipment and leasehold improvements, gross	$ 27	$ 27