Fair value of financial instruments and marketable securities (Details 4) (USD $)
In Thousands, except Per Share data, unless otherwise specified |
3 Months Ended | 12 Months Ended | 3 Months Ended | 12 Months Ended | ||||
---|---|---|---|---|---|---|---|---|
Jun. 30, 2013
Common stock
|
Mar. 31, 2014
Warrant
|
Mar. 31, 2014
Warrant
Minimum
|
Dec. 31, 2013
Warrant
Minimum
|
Mar. 31, 2014
Warrant
Maximum
|
Dec. 31, 2013
Warrant
Maximum
|
Mar. 31, 2014
Warrant
Common stock
|
Dec. 31, 2013
Warrant
Common stock
|
|
Changes in the fair value of warrant liability | ||||||||
Beginning balance | $ 58 | |||||||
Change in fair value of warrant liability | 55 | |||||||
Ending balance | $ 113 | |||||||
Assumption used to estimate the fair value of warrant liability by utilizing the Black-Scholes option-pricing model | ||||||||
Volatility (as a percent) | 58.00% | 61.00% | 90.00% | 89.00% | ||||
Risk-free interest rate (as a percent) | 0.03% | 0.07% | 1.73% | 2.10% | ||||
Strike price (in dollars per share) | $ 128.00 | $ 128.00 | $ 2,520.00 | $ 2,520.00 | ||||
Fair value of shares (in dollars per share) | $ 15.00 | $ 26.14 | $ 16.97 | |||||
Expected life | 22 days | 3 months 18 days | 5 years 5 months 23 days | 5 years 8 months 12 days |