Subsequent events - Additional Information (Detail)			0 Months Ended
	Jun. 30, 2014	Dec. 31, 2013	Jul. 17, 2014 Subsequent Event [Member] Two Thousand Eleven Equity Incentive Plan [Member]	Jul. 17, 2014 Subsequent Event [Member] Minimum [Member] Two Thousand Eleven Equity Incentive Plan [Member]	Jul. 17, 2014 Subsequent Event [Member] Maximum [Member] Two Thousand Eleven Equity Incentive Plan [Member]
Subsequent Event [Line Items]
Common stock authorized	75,000,000	75,000,000		6,800,000	8,800,000
Additional number of common shares authorized			2,000,000