Capitalization (Convertible Preferred Stock) (Details) (USD $) In Thousands, except Share data, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Apr. 07, 2014
Temporary Equity [Line Items]
Carrying Values	$ 0	$ 52,571
Conversion of convertible preferred stock
Temporary Equity [Line Items]
Shares Authorized		29,691,524
Shares Outstanding		28,820,481
Carrying Values		52,571
Liquidation Preference		72,772
Series A
Temporary Equity [Line Items]
Shares Authorized		6,154,000
Shares Outstanding		6,154,000
Carrying Values		4,000
Liquidation Preference		6,118
Original Issue Price per share			$ 0.65
Conversion Price per share			$ 1.30
Series B
Temporary Equity [Line Items]
Shares Authorized		13,588,160
Shares Outstanding		13,562,986
Carrying Values		21,087
Liquidation Preference		30,754
Original Issue Price per share			$ 1.55556
Conversion Price per share			$ 3.11112
Series C
Temporary Equity [Line Items]
Shares Authorized		4,765,173
Shares Outstanding		3,919,306
Carrying Values		9,484
Liquidation Preference		12,779
Original Issue Price per share			$ 2.42729
Conversion Price per share			$ 4.85458
Series D
Temporary Equity [Line Items]
Shares Authorized		5,184,191
Shares Outstanding		5,184,189
Carrying Values		18,000
Liquidation Preference		$ 23,121
Original Issue Price per share			$ 3.55603
Conversion Price per share			$ 7.11206