Accounting policies (Schedule of Assumptions Used to Value Convertible Notes) (Details) - $ / shares |
12 Months Ended | |||
|---|---|---|---|---|
Apr. 05, 2017 |
Dec. 31, 2017 |
Nov. 13, 2017 |
Mar. 20, 2017 |
|
| Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items] | ||||
| Market price per share (USD/share) | $ 2.75 | $ 1.06 | $ 1.20 | $ 2.85 |
| Exercise price (USD/share) | $ 2.75 | $ 1.00 | ||
| Risk-free rate | 1.83% | 2.00% | ||
| Dividend yield | 0.00% | 0.00% | ||
| Expected term/Contractual life (years) | 4 years | 3 years 3 months 4 days | ||
| Expected volatility | 106.46% | 110.46% |