Quarterly report pursuant to Section 13 or 15(d)

Stock options and warrants (Stock incentive plan options) (Narrative) (Details)

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Stock options and warrants (Stock incentive plan options) (Narrative) (Details) (USD $)
 3 Months Ended 9 Months Ended
Sep. 30, 2013
Sep. 30, 2012
Sep. 30, 2013
Sep. 30, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Share-based compensation, operating expense $ 332,250 $ 254,938 $ 1,227,597 $ 676,359
Stock Incentive Plan [Member]
        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Share-based compensation, operating expense 332,000 240,000 1,206,000 316,000
Options granted     525,603  
Options granted, exercise price     $ 2.06  
Options forfeited     13,394  
Options forfeited, exercise price     $ 27.69  
Common stock options exercised, shares         
Vested and exercisable value 1,055,000 1,363,000 1,055,000 1,363,000
Expected to vest 606,000   606,000  
Unrecognized compensation cost $ 480,000   $ 480,000  
Unrecognized compensation cost, period for recognition     1 year  
Stock Incentive Plan [Member] | Minimum [Member]
        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Expiration period     3 years  
Stock Incentive Plan [Member] | Maximum [Member]
        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Expiration period     5 years  
Stock Incentive Plan [Member] | Independent Directors [Member]
        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Expiration period     10 years  
Options granted     209,333  
Options granted, exercise price     $ 2.10  
Vesting period     1 year  
Stock Incentive Plan [Member] | Officers [Member]
        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Expiration period     10 years  
Options granted     292,000  
Options granted, exercise price     $ 2.04  
Vesting period     24 months  
Stock Incentive Plan [Member] | Employees [Member]
        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Expiration period     10 years  
Options granted     24,270  
Options granted, exercise price     $ 2.02  
Vesting period     25 months  
Options forfeited     13,394 36,446
Options forfeited, vested 6,086 11,970 6,086 11,970
Options forfeited, exercise price     $ 27.69 $ 38.88