Notes Payable - Maturities of Long-Term Debt (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Estimated future principal payments
2017	$ 3,333
2018	2,500
Total	5,833
Less: discount for warrants and costs paid to lender	(111)
Less: current portion	(3,243)
Notes payable, net of current portion and discount	2,479	$ 5,720
Credit Facility
Estimated future principal payments
Interest expense	$ 800	$ 1,000	$ 200