Consolidated Statements of Changes in Redeemable Convertible Preferred Stock and Stockholders' Equity (Deficit) (Parenthetical) - USD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Net of issuance costs $ 3,304 $ 30
Series E Redeemable Convertible Preferred Stock [Member]    
Net of issuance costs   $ 94