Summary of Significant Accounting Policies - Securities Excluded from Calculation of Weighted-Average Shares Outstanding (Detail)	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Shares of Convertible Preferred Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Securities excluded from calculation of weighted-average shares outstanding		1,917,120		1,917,120
Shares Underlying Options Outstanding [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Securities excluded from calculation of weighted-average shares outstanding	1,269,320	546,490	1,269,320	546,490
Shares Underlying Warrants Outstanding [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Securities excluded from calculation of weighted-average shares outstanding	6,033,050	5,466,470	6,033,050	5,466,470