Consolidated Statements of Redeemable Convertible Preferred Stock and Stockholders' Equity (Parenthetical) - USD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Underwriting fees and issuance costs $ 445 $ 10,751
Series C Redeemable Convertible Preferred Stock [Member]    
Underwriting fees and issuance costs $ 445