v3.3.0.814
Fair Value Measurements (Details 3) - USD ($)
$ in Thousands
3 Months Ended 9 Months Ended
Sep. 30, 2015
Sep. 30, 2014
Sep. 30, 2015
Sep. 30, 2014
Reconciliations of the beginning and ending balances for liabilities measured at fair value on a recurring basis using significant unobservable inputs (i.e. Level 3)        
Balance at the beginning of the period $ 6,982 $ 16,129 $ 9,418 $ 28,830
Change in fair value of common stock warrants (2,167) (485) (4,603) 58,371
Issuance of common stock warrants       11,773
Exercise of common stock warrants (22) (115) (22) (83,445)
Balance at the end of the period $ 4,793 $ 15,529 $ 4,793 $ 15,529