Fair value measurements (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2017	Dec. 31, 2016
Fair value measurements
Warrant liability - related party	$ 1,025	$ 976
Fair value Assumptions
Company's ending stock price (in dollars per share)	$ 0.63	$ 0.58
Company's stock volatility (as a percent)	110.00%	110.00%
Risk free interest rate (as a percent)	1.39%	1.39%
Recurring
Fair value measurements
Cash and cash equivalents	$ 2,065	$ 2,588
Trade accounts receivable	445	380
Trade accounts receivable - related party	746	643
Short-term investments	281	334
Assets	3,537	3,945
Warrant liability - related party	1,025	976
Warrant liability	935	922
Liabilities	1,960	1,898
Recurring | Level 1
Fair value measurements
Cash and cash equivalents	2,065	2,588
Trade accounts receivable	445	380
Trade accounts receivable - related party	746	643
Short-term investments	281	334
Assets	3,537	3,945
Recurring | Level 3
Fair value measurements
Warrant liability - related party	1,025	976
Warrant liability	935	922
Liabilities	$ 1,960	$ 1,898