Stock Options and Warrants, Options by Exercise Price Range (Details) (USD $)
12 Months Ended
Dec. 31, 2014
Stock Options [Member]  
Share based compensation, shares authorized under significant ranges of outstanding stock option plans in period [Abstract]  
Number of Options (in shares) 10,040,735
Weighted-Average Remaining Contractual Life 8 years 5 months 16 days
Weighted-Average Exercise Price (in dollars per share) $ 2.87
Number of Options Exercisable (in shares) 5,593,654
Weighted-Average Contractual Life 8 years 5 months 16 days
Weighted-Average Exercise Price, Options Exercisable (in dollars per share) $ 3.25
Warrants [Member]  
Share based compensation, shares authorized under significant ranges of outstanding stock option plans in period [Abstract]  
Number of Options (in shares) 7,349,760
Weighted-Average Remaining Contractual Life 1 year 8 months 16 days
Weighted-Average Exercise Price (in dollars per share) $ 4.27
Number of Options Exercisable (in shares) 7,149,760
Weighted-Average Exercise Price, Options Exercisable (in dollars per share) $ 4.32
Range $ 1.83 - 2.50 [Member] | Stock Options [Member]  
Share based compensation, shares authorized under significant ranges of outstanding stock option plans in period [Abstract]  
Range of Exercise Prices, Lower Range (in dollars per share) $ 1.83
Range of Exercise Prices, Upper Range (in dollars per share) $ 2.50
Number of Options (in shares) 7,932,558
Weighted-Average Remaining Contractual Life 8 years 11 months 26 days
Weighted-Average Exercise Price (in dollars per share) $ 2.19
Number of Options Exercisable (in shares) 3,801,902
Weighted-Average Contractual Life 8 years 11 months 26 days
Weighted-Average Exercise Price, Options Exercisable (in dollars per share) $ 2.17
Range $ 2.51 - 3.50 [Member] | Stock Options [Member]  
Share based compensation, shares authorized under significant ranges of outstanding stock option plans in period [Abstract]  
Range of Exercise Prices, Lower Range (in dollars per share) $ 2.51
Range of Exercise Prices, Upper Range (in dollars per share) $ 3.50
Number of Options (in shares) 774,482
Weighted-Average Remaining Contractual Life 8 years 10 months 20 days
Weighted-Average Exercise Price (in dollars per share) $ 2.78
Number of Options Exercisable (in shares) 691,387
Weighted-Average Contractual Life 8 years 10 months 20 days
Weighted-Average Exercise Price, Options Exercisable (in dollars per share) $ 2.75
Range $ 3.51 - 8.00 [Member] | Stock Options [Member]  
Share based compensation, shares authorized under significant ranges of outstanding stock option plans in period [Abstract]  
Range of Exercise Prices, Lower Range (in dollars per share) $ 3.51
Range of Exercise Prices, Upper Range (in dollars per share) $ 8.00
Number of Options (in shares) 989,201
Weighted-Average Remaining Contractual Life 6 years 0 months 14 days
Weighted-Average Exercise Price (in dollars per share) $ 6.27
Number of Options Exercisable (in shares) 755,871
Weighted-Average Contractual Life 6 years 0 months 14 days
Weighted-Average Exercise Price, Options Exercisable (in dollars per share) $ 6.57
Range $ 8.01 - 32.55 [Member] | Stock Options [Member]  
Share based compensation, shares authorized under significant ranges of outstanding stock option plans in period [Abstract]  
Range of Exercise Prices, Lower Range (in dollars per share) $ 8.01
Range of Exercise Prices, Upper Range (in dollars per share) $ 32.55
Number of Options (in shares) 344,494
Weighted-Average Remaining Contractual Life 2 years 4 months 17 days
Weighted-Average Exercise Price (in dollars per share) $ 8.93
Number of Options Exercisable (in shares) 344,494
Weighted-Average Contractual Life 2 years 4 months 17 days
Weighted-Average Exercise Price, Options Exercisable (in dollars per share) $ 8.93
Range $2.10 - 2.60 [Member] | Warrants [Member]  
Share based compensation, shares authorized under significant ranges of outstanding stock option plans in period [Abstract]  
Range of Exercise Prices, Lower Range (in dollars per share) $ 2.10
Range of Exercise Prices, Upper Range (in dollars per share) $ 2.60
Number of Options (in shares) 645,716
Weighted-Average Remaining Contractual Life 3 years 0 months 18 days
Weighted-Average Exercise Price (in dollars per share) $ 2.42
Number of Options Exercisable (in shares) 445,716
Weighted-Average Exercise Price, Options Exercisable (in dollars per share) $ 2.38
Range $2.61 - 3.60 [Member] | Warrants [Member]  
Share based compensation, shares authorized under significant ranges of outstanding stock option plans in period [Abstract]  
Range of Exercise Prices, Lower Range (in dollars per share) $ 2.61
Range of Exercise Prices, Upper Range (in dollars per share) $ 3.60
Number of Options (in shares) 125,000
Weighted-Average Remaining Contractual Life 0 years 10 months 10 days
Weighted-Average Exercise Price (in dollars per share) $ 3.00
Number of Options Exercisable (in shares) 125,000
Weighted-Average Exercise Price, Options Exercisable (in dollars per share) $ 3.00
Range $3.61 - 4.60 [Member] | Warrants [Member]  
Share based compensation, shares authorized under significant ranges of outstanding stock option plans in period [Abstract]  
Range of Exercise Prices, Lower Range (in dollars per share) $ 3.61
Range of Exercise Prices, Upper Range (in dollars per share) $ 4.60
Number of Options (in shares) 6,496,899
Weighted-Average Remaining Contractual Life 1 year 6 months 25 days
Weighted-Average Exercise Price (in dollars per share) $ 4.47
Number of Options Exercisable (in shares) 6,496,899
Weighted-Average Exercise Price, Options Exercisable (in dollars per share) $ 4.47
Range $4.61 - 5.60 [Member] | Warrants [Member]  
Share based compensation, shares authorized under significant ranges of outstanding stock option plans in period [Abstract]  
Range of Exercise Prices, Lower Range (in dollars per share) $ 4.61
Range of Exercise Prices, Upper Range (in dollars per share) $ 5.60
Number of Options (in shares) 82,145
Weighted-Average Remaining Contractual Life 3 years 2 months 12 days
Weighted-Average Exercise Price (in dollars per share) $ 5.41
Number of Options Exercisable (in shares) 82,145
Weighted-Average Exercise Price, Options Exercisable (in dollars per share) $ 5.41