Loans Payable (Details) $ / shares in Units, $ in Thousands	1 Months Ended		12 Months Ended
	Dec. 31, 2015 USD ($) item $ / shares shares	Sep. 30, 2014 USD ($) tranche $ / shares shares	Dec. 31, 2019 USD ($) $ / shares shares	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Mar. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Long Term Debt
Gross proceeds			$ 3,167
Aggregate principal balance outstanding			3,163
Interest expense			931	$ 2,231	$ 2,780
Debt discount and debt issuance costs			4
Amortization of debt discount and issuance costs			100	200	300
Loan and security agreement
Long Term Debt
Face amount		$ 35,000
Debt number of tranches | tranche		3
Gross proceeds			$ 3,167	15,833
Final payment fee percentage			6.60%
Interest expense			$ 600	$ 1,400	$ 1,700
Debt discount and debt issuance costs		$ 1,000
Term Loan A
Long Term Debt
Face amount		$ 2,000
Interest rate (as a percent)			6.50%
Term Loan A | Common Stock | Warrants
Long Term Debt
Number of shares that can be purchased upon exercise of warrants (in shares) | shares		7,678	5,728
Exercise price | $ / shares		$ 5.8610
Term Loan B
Long Term Debt
Face amount	$ 16,500
Interest rate (as a percent)			6.50%
Term Loan B | Common Stock | Warrants
Long Term Debt
Number of shares that can be purchased upon exercise of warrants (in shares) | shares	34,961
Exercise price | $ / shares	$ 10.6190
Term Loan C
Long Term Debt
Face amount						$ 10,000
Debt Instrument Borrowing Capacity	$ 16,500
Remaining amount available							$ 10,000
Number of specified triggers needed to be satisfied to draw on loan | item	1
Interest rate (as a percent)			6.98%
Prepayment fee percent			1.00%
Term Loan C | Common Stock | Warrants
Long Term Debt
Number of shares that can be purchased upon exercise of warrants (in shares) | shares			62,241
Exercise price | $ / shares			$ 3.6150
Term Loans A, B, and C
Long Term Debt
Aggregate principal balance outstanding			$ 3,200