Income taxes - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Income Tax [Line Items]
Operating Loss Carry forwards Expiration Period	2034
Income Tax Expense (Benefit)	$ 2,944,000	$ (906,000)
Operating Loss Carryforwards	$ 9,000,000
Operating Loss Carryforwards, Limitations On Use	Approximately $6,750,000 of the Companys $9,000,000 of NOLs are subject to annual limitations of $1,300,000.