Notes Payable - Maturities of Long-Term Debt (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
Future principal payments
Remainder 2017	$ 2,500
2018	2,500
Total	5,000
Less: discount for warrants and costs paid to lenders	(83)
Less: current portion	(3,260)
Notes payable, net of current portion and discount	1,657		$ 2,479
Credit Facility
Future principal payments
Interest expense	$ 100	$ 200