Commitments and contingencies - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2011	Dec. 31, 2011 Research and Development Expense [Member]	Dec. 31, 2013 Selling General and Administrative Expenses [Member]	Dec. 31, 2012 Selling General and Administrative Expenses [Member]
Commitments and Contingencies Disclosure [Line Items]
Settlement agreement amount				$ 214,000	$ 554,000
Settlement of trade debt		32,000	15,000	214,000	546,000
Gain On Liquidation Of Subsidiary	$ 149,000			$ 149,000	$ 0