Supplemental Disclosure of Cash Flow Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Supplemental disclosure of cash flow information:
Cash paid for interest	$ 72	$ 93	$ 49
Supplemental disclosure of non-cash financing and investing activities:
Non-cash property additions	425	$ 123	324
Accrued 2013 financing transaction costs paid in 2014	$ 166
Series D Convertible Preferred Stock
Supplemental disclosure of non-cash financing and investing activities:
Conversion of preferred stock to common stock			5,464
Series E Convertible Preferred Stock
Supplemental disclosure of non-cash financing and investing activities:
Conversion of preferred stock to common stock			$ 5,528