Debt - Future Principal Payments on Debt (Details) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Line Of Credit Facility [Line Items]
Total debt, net carrying amount	$ 19,973	$ 22,131
Hercules Term Loan
Line Of Credit Facility [Line Items]
Total debt, net carrying amount	17,824	$ 19,070
Magna August Note
Line Of Credit Facility [Line Items]
Total debt, net carrying amount	2,149
Convertible Notes Payable
Line Of Credit Facility [Line Items]
2015	1,790
2016	9,815
2017	8,567
2018	818
Total debt, net carrying amount	20,990
Convertible Notes Payable | Hercules Term Loan
Line Of Credit Facility [Line Items]
2015	1,790
2016	7,666
2017	8,567
2018	818
Total debt, net carrying amount	18,841
Convertible Notes Payable | Magna August Note
Line Of Credit Facility [Line Items]
2015	0
2016	2,149
2017	0
2018	0
Total debt, net carrying amount	$ 2,149