Stockholders' Equity (Deficit) (Details)				12 Months Ended
	Nov. 06, 2015 USD ($)	Nov. 10, 2014 USD ($)	Oct. 30, 2013 USD ($) $ / shares shares	Dec. 31, 2015 USD ($) vote $ / shares shares	Dec. 31, 2014 USD ($) $ / shares shares	Dec. 31, 2013 USD ($) shares	Oct. 30, 2015 $ / shares	Oct. 24, 2013 shares
Class of Stock [Line Items]
Common stock, shares issued			7,728,000
Common stock, offering price per share (in dollars per share) | $ / shares							$ 10.00
Net proceeds from initial public offering | $			$ 68,300,000	$ 0	$ 0	$ 71,870,000
Underwriting discounts and commissions | $			5,400,000
Proceeds from notes payable to related parties | $			$ (3,600,000)	$ 0	$ 0	(3,644,000)
Conversion of convertible securities to common stock			12,120,531
Debt conversion, shares issued			1,860,363
IPO conversion price (in dollars per share) | $ / shares			$ 10.00
Common stock, shares authorized			150,000,000	150,000,000	150,000,000
Common stock, par value (in dollars per share) | $ / shares			$ 0.001	$ 0.001	$ 0.001
Decrease in preferred stock			15,000,000	15,000,000	15,000,000
Preferred stock, par value (in dollars per share) | $ / shares			$ 0.001	$ 0.001	$ 0.001
Shelf registration statement, aggregate dollar amount | $					$ 0
Proceeds from sale of common stock | $				$ 50,451,000	$ 0	$ 0
Number of voting rights | vote				1
Common Stock
Class of Stock [Line Items]
Common stock, shares issued				1,754,556		7,728,000
Underwriting discounts and commissions | $				$ 1,496,000		$ 5,410,000
Conversion of convertible securities to common stock						12,120,531
Amount available under sales agreement | $				$ 48,100,000
Stock offering underwriter overallotment option
Class of Stock [Line Items]
Common stock, shares issued			1,008,000
Employee stock purchase plan
Class of Stock [Line Items]
Equity awards			645,814
2013 equity plan
Class of Stock [Line Items]
Equity awards			3,229,068
Maximum
Class of Stock [Line Items]
Shelf registration statement, aggregate dollar amount | $		$ 150,000,000.0
Conversion one | Convertible Preferred Stock
Class of Stock [Line Items]
Warrants exercise to purchase convertible preferred stock								297,366
Conversion of convertible securities to common stock			297,366
Conversion two | Convertible Preferred Stock
Class of Stock [Line Items]
Warrants exercise to purchase convertible preferred stock			186,248
Conversion of convertible securities to common stock			186,248
Conversion three | Convertible Preferred Stock
Class of Stock [Line Items]
Conversion of convertible securities to common stock			12,120,531
Conversion four
Class of Stock [Line Items]
Warrants to purchase common stock			717,801
Conversion four | Convertible Preferred Stock
Class of Stock [Line Items]
Warrants to purchase common stock			717,801
Cantor Fitzgerald and Co. | Common Stock
Class of Stock [Line Items]
Common stock issued and sold under sales agreement				1,754,556	0
Proceeds from sale of common stock | $				$ 50,500,000
Sale of stock, commissions, percentage of gross sales				3.00%
Cantor Fitzgerald and Co. | Maximum | Common Stock
Class of Stock [Line Items]
Shelf registration statement, aggregate dollar amount | $		$ 50,000,000.0
RBC Capital Markets, LLC and Cantor Fitzgerald & Co | Maximum | Common Stock
Class of Stock [Line Items]
Prospectus supplement, aggregate dollar amount | $	$ 50,000,000.0