Formation and Business of the Company (Details)					12 Months Ended
	Sep. 23, 2015 USD ($) $ / shares shares	Nov. 03, 2014 USD ($) $ / shares shares	Oct. 10, 2014	Oct. 09, 2014	Dec. 31, 2015 shares	Dec. 31, 2014 shares	Dec. 31, 2013 shares
Formation and Business of the Company
Proceeds from the issuance of common stock, net of underwriting discounts, commissions and offering expenses | $		$ 0
Convertible preferred stock
Formation and Business of the Company
Convertible preferred stock, shares outstanding | shares							24,593,087
Common stock
Formation and Business of the Company
Conversion rate			2.75	1.00
Proceeds from IPO/follow-on offering, net of costs (in shares) | shares					3,000,000	5,750,000
Shares issued on conversion of Series A, Series B and Series C preferred stock | shares		8,942,925
Common stock | IPO
Formation and Business of the Company
Proceeds from IPO/follow-on offering, net of costs (in shares) | shares		5,750,000
Public offering price (in dollars per share) | $ / shares		$ 15.00
Net proceeds after deducting underwriting discounts and commissions and offering expenses | $		$ 77,000,000
Payment of underwriting discounts and commissions and offering expenses | $		$ 9,200,000
Common stock | Follow-On Offering
Formation and Business of the Company
Proceeds from IPO/follow-on offering, net of costs (in shares) | shares	3,000,000
Public offering price (in dollars per share) | $ / shares	$ 22.00
Payment of underwriting discounts and commissions and offering expenses | $	$ 4,000,000
Offering expenses | $	600,000
Proceeds from the issuance of common stock, net of underwriting discounts, commissions and offering expenses | $	$ 61,400,000
Common stock | Over allotment option exercised by underwriters
Formation and Business of the Company
Proceeds from IPO/follow-on offering, net of costs (in shares) | shares		750,000
Preferred Stock
Formation and Business of the Company
Conversion rate				2.75