Income taxes - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Income Tax [Line Items]
Income Tax Expense (Benefit)	$ (906,000)	$ (3,576,000)
Operating Loss Carryforwards	$ 16,000,000
Operating Loss Carryforwards, Limitations On Use	Approximately $8,000,000 of the Companys $16,000,000 of NOLs are subject to annual limitations of $1,300,000
Operating Loss Carryforwards Expiration Period	2033