Warrants - Additional Information (Details) - USD ($)				3 Months Ended			9 Months Ended		12 Months Ended
	May. 11, 2015	Jan. 15, 2015	Aug. 22, 2014	Sep. 30, 2015	Dec. 31, 2014	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014	May. 31, 2015
Class Of Warrant Or Right [Line Items]
Share price					$ 0.13				$ 0.13
Expected risk-free interest rate					1.60%				1.20%
Expected volatility					75.00%				70.00%
Expected term					7 years				4 years 1 month 6 days
Expected dividend yield					0.00%
Fair value of warrants					$ 741,828				$ 741,828
Common stock, at the initial public offering price per shares	$ 14.00
Preferred stock, shares issued				0	0		0		0
Class of Warrant or Right, Outstanding				0			0
Proceeds from exercise of E warrants							$ 8,948
Fair value of convertible preferred stock warrant liability				$ 0	$ 730,543		0		$ 730,543
Loss on change in fair value of convertible preferred stock warrants				$ 0		$ 0	$ 239,683	$ 56,323
IPO
Class Of Warrant Or Right [Line Items]
Common stock, at the initial public offering price per shares	$ 14.00
Series E Stock
Class Of Warrant Or Right [Line Items]
Share price			$ 0.31
Warrants exercise price			$ 0.2189
Expected risk-free interest rate			1.60%
Expected volatility			70.00%
Expected term			4 years 6 months
Expected dividend yield			8.00%
Series C-1 Redeemable Convertible Preferred Stock
Class Of Warrant Or Right [Line Items]
Warrants exercise price				$ 37.16			$ 37.16
Preferred stock warrants forfeited and cancelled	1,290,350
Class of Warrant or Right, Outstanding					1,290,350				1,290,350
Series C-2 Redeemable Convertible Preferred Stock
Class Of Warrant Or Right [Line Items]
Warrants exercise price				$ 24.23			$ 24.23
Class of Warrant or Right, Outstanding					157,912				157,912
Series C-2 Redeemable Convertible Preferred Stock | IPO
Class Of Warrant Or Right [Line Items]
Warrants issued to acquire shares	1,488
Warrants exercise price	$ 24.23
Class of Warrant or Right, Outstanding				1,488			1,488
Series D Convertible Preferred Stock
Class Of Warrant Or Right [Line Items]
Warrants exercise price				$ 1.07			$ 1.07
Common stock, at the initial public offering price per shares				$ 14.00			$ 14.00
Preferred stock, shares issued				723,050			723,050
Class of Warrant or Right, Outstanding				769,059	769,059		769,059		769,059
Proceeds from exercise of E warrants							$ 1,752
Conversion of stock, shares issued	6,729
Series E Loan Warrants
Class Of Warrant Or Right [Line Items]
Warrants issued to acquire shares			2,512,562							23,396
Warrants exercise price			$ 0.2189							$ 23.51
Warrants expiration date							Aug. 22, 2024
Warrants exercise price			$ 0.12
Fair value of warrants			$ 301,507		$ 301,507				$ 301,507
Series E Loan Warrants | IPO
Class Of Warrant Or Right [Line Items]
Warrants issued to acquire shares	23,396
Warrants exercise price	$ 14.00
Convertible Note Warrants
Class Of Warrant Or Right [Line Items]
Warrants issued to acquire shares		9,311,586
Warrants exercise price		$ 0.2189		$ 14.00			$ 14.00
Warrants expiration date							Jan. 15, 2022
Aggregate consideration		$ 1,354
Convertible Note Warrants | IPO
Class Of Warrant Or Right [Line Items]
Warrants issued to acquire shares	144,772
Warrants exercise price	$ 14.00
Class of Warrant or Right, Outstanding				144,772			144,772