Loan facility - Additional Information (Detail) (USD $)	6 Months Ended	12 Months Ended	0 Months Ended		6 Months Ended
	Jun. 30, 2014	Dec. 31, 2013	Mar. 28, 2014 Silicon Valley Bank [Member]	Oct. 30, 2013 Silicon Valley Bank [Member]	Jun. 30, 2014 Silicon Valley Bank [Member]	Oct. 23, 2013 Silicon Valley Bank [Member]	Oct. 23, 2013 Silicon Valley Bank [Member] Warrants to Purchase Series C Convertible Preferred Stock [Member]	Jun. 30, 2014 Silicon Valley Bank [Member] Warrants to Purchase Common Stock [Member]
Line of Credit Facility [Line Items]
Term loan facility with Silicon Valley Bank						$ 4,000,000
Term loan, amount borrowed		2,500,000		2,500,000
Warrants to purchase per share							$ 10.56
Warrants to purchase shares of stock, shares							11,363
Warrants exercisable								11,363
Warrants expire					2023
Term loan repayment	2,609,844		2,609,844
Term loan, loss on extinguishment of debt			$ 213,511