Capitalization (Narrative) (Details)			12 Months Ended
	Apr. 07, 2014 USD ($) $ / shares shares	Mar. 18, 2014	Dec. 31, 2015 USD ($) shares	Dec. 31, 2014 shares	Dec. 31, 2013 USD ($) $ / shares shares	Apr. 01, 2014 $ / shares shares	Mar. 14, 2014 shares	Jan. 12, 2010 $ / shares	Mar. 01, 2009 $ / shares
Class of Stock [Line Items]
Common stock, shares authorized			500,000,000	500,000,000	73,380,126		80,608,856
Proceeds from Issuance Initial Public Offering | $	$ 86,200,000
Deferred offering costs included in accounts payable and accrued expenses | $	$ 3,500,000
Convertible preferred stock, terms of conversion, proceeds from issuance initial public offering, net of offering costs, minimum | $					$ 20,000,000
Convertible preferred stock, terms of conversion, pre-offering enterprise value, minimum | $					$ 250,000,000
Convertible preferred stock, terms of conversion, holder consent vote, percent, minimum					75.00%
Number of Shares Authorized			12,464,864
Dividends | $			$ 0
Common Stock
Class of Stock [Line Items]
Initial public offering, shares sold during IPO	6,432,445			6,432,000
Initial public offering, shares sold during IPO, over-allotment option	1,015,649
Initial public offering, shares sold by existing stockholders	1,354,199
Share Price | $ / shares	$ 15					$ 15.00
Conversion of convertible preferred stock to common stock (in shares)				14,696,000
Reverse stock split, conversion ratio		0.5
Convertible preferred stock warrants
Class of Stock [Line Items]
Class of Warrant or Right, Number of Securities Called by Warrants or Rights	25,174
Series B warrants
Class of Stock [Line Items]
Exercise price of warrants | $ / shares									$ 1.55556
Common stock warrants
Class of Stock [Line Items]
Conversion of convertible preferred stock to common stock (in shares)	286,055
Number of securities called by each warrant	12,587
Series C warrants
Class of Stock [Line Items]
Class of warrant or right, outstanding						845,867
Exercise price of warrants | $ / shares								$ 2.42729
Common Class A
Class of Stock [Line Items]
Common stock, shares authorized					32,500,000
Conversion of convertible preferred stock to common stock (in shares)	14,410,238
Reverse stock split, conversion ratio		0.5
Conversion of stock, shares converted	1
Common Class B
Class of Stock [Line Items]
Common stock, shares authorized					4,190,063
Conversion of convertible preferred stock
Class of Stock [Line Items]
Temporary equity, shares authorized					29,691,524
Temporary equity, amount of preferred dividends in arrears | $					$ 19,700,000
Series A
Class of Stock [Line Items]
Temporary equity, shares authorized					6,154,000
Temporary equity, dividend rate, per-dollar-amount | $ / shares					$ 0.052
Series B
Class of Stock [Line Items]
Temporary equity, shares authorized					13,588,160
Temporary equity, dividend rate, per-dollar-amount | $ / shares					$ 0.1244480
Series C
Class of Stock [Line Items]
Temporary equity, shares authorized					4,765,173
Temporary equity, dividend rate, per-dollar-amount | $ / shares					$ 0.1941832
Series D
Class of Stock [Line Items]
Temporary equity, shares authorized					5,184,191
Temporary equity, dividend rate, per-dollar-amount | $ / shares					$ 0.2844824
Common Stock
Class of Stock [Line Items]
Common stock, shares authorized	500,000,000
Preferred Stock
Class of Stock [Line Items]
Preferred stock, shares authorized	10,000,000		10,000,000	10,000,000