Convertible Preferred Stock Warrants (Details) (USD $)	1 Months Ended	3 Months Ended	9 Months Ended
	Jun. 30, 2013	Sep. 30, 2013	Sep. 30, 2013
Convertible preferred stock warrant
Amount drawn down of term loan	$ 5,000,000
Assumptions used to calculate fair value of warrant upon issuance using Black-Scholes option-pricing valuation model
Preferred stock value (in dollars per share)		$ 12.12	$ 12.12
Amount of change in the fair value reported as an expense in other income (expense), net			77,000
Convertible Preferred Stock Warrant
Convertible preferred stock warrant
Number of shares of preferred stock that can be purchased by each warrant	198,412
Exercise price (in dollars per share)	$ 1.89
Number of shares for which warrant became exercisable	99,206
Number of shares for which warrant will become exercisable upon drawing the second term loan	99,206
Number of shares for which warrant will become exercisable in the event of conversion of outstanding Series C convertible preferred stock into common stock	24,801
Number of aggregate shares for which warrant will become exercisable in the event of conversion of outstanding Series C convertible preferred stock into common stock if Company draws down the second term loan	49,602
Exercise price of warrants in the event of conversion of outstanding Series C convertible preferred stock into common stock (in dollars per share)	$ 7.56
Fair value of currently exercisable portion of the warrant	175,000	252,000	252,000
Assumptions used to calculate fair value of warrant upon issuance using Black-Scholes option-pricing valuation model
Preferred stock value (in dollars per share)	$ 2.40	$ 3.25	$ 3.25
Contractual term	7 years 3 months 18 days		7 years 30 days
Risk-free interest rate (as a percent)	2.10%		2.02%
Expected volatility (as a percent)	73.70%		75.63%
Expected dividend yield (as a percent)	0.00%		0.00%
Amount of change in the fair value reported as an expense in other income (expense), net		$ 77,000	$ 77,000