Stock Options and Equity-Classified Warrants, Options by Exercise Price Range (Details)	12 Months Ended
	Dec. 31, 2015 $ / shares shares
Stock Options [Member]
Share based compensation, shares authorized under significant ranges of outstanding stock option plans in period [Abstract]
Number of Options (in shares) | shares	14,209,576
Weighted-Average Remaining Contractual Life	8 years 3 months 22 days
Weighted-Average Exercise Price (in dollars per share)	$ 3.10
Number of Options Exercisable (in shares) | shares	8,650,878
Weighted-Average Contractual Life	7 years 7 months 17 days
Weighted-Average Exercise Price, Options Exercisable (in dollars per share)	$ 3.42
Warrants [Member]
Share based compensation, shares authorized under significant ranges of outstanding stock option plans in period [Abstract]
Number of Options (in shares) | shares	7,225,472
Weighted-Average Remaining Contractual Life	9 months 29 days
Weighted-Average Exercise Price (in dollars per share)	$ 4.28
Number of Options Exercisable (in shares) | shares	7,225,472
Weighted-Average Exercise Price, Options Exercisable (in dollars per share)	$ 4.28
Range $ 1.75 - 2.00 [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)	1.75
Range of Exercise Prices, Upper Range (in dollars per share)	$ 2.00
Number of Options (in shares) | shares	1,374,500
Weighted-Average Remaining Contractual Life	6 years 11 months 12 days
Weighted-Average Exercise Price (in dollars per share)	$ 1.83
Number of Options Exercisable (in shares) | shares	1,374,500
Weighted-Average Contractual Life	6 years 11 months 12 days
Weighted-Average Exercise Price, Options Exercisable (in dollars per share)	$ 1.83
Range $ 2.01 - 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)	2.01
Range of Exercise Prices, Upper Range (in dollars per share)	$ 2.50
Number of Options (in shares) | shares	8,215,556
Weighted-Average Remaining Contractual Life	9 years 1 month 20 days
Weighted-Average Exercise Price (in dollars per share)	$ 2.33
Number of Options Exercisable (in shares) | shares	3,280,923
Weighted-Average Contractual Life	8 years 6 months 14 days
Weighted-Average Exercise Price, Options Exercisable (in dollars per share)	$ 2.30
Range $ 2.51 - 4.00 [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)	2.51
Range of Exercise Prices, Upper Range (in dollars per share)	$ 4.00
Number of Options (in shares) | shares	986,980
Weighted-Average Remaining Contractual Life	8 years 22 days
Weighted-Average Exercise Price (in dollars per share)	$ 2.89
Number of Options Exercisable (in shares) | shares	919,481
Weighted-Average Contractual Life	8 years 4 days
Weighted-Average Exercise Price, Options Exercisable (in dollars per share)	$ 2.87
Range $ 4.01 - 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)	4.01
Range of Exercise Prices, Upper Range (in dollars per share)	$ 32.55
Number of Options (in shares) | shares	3,632,540
Weighted-Average Remaining Contractual Life	7 years 11 days
Weighted-Average Exercise Price (in dollars per share)	$ 5.38
Number of Options Exercisable (in shares) | shares	3,075,974
Weighted-Average Contractual Life	6 years 10 months 6 days
Weighted-Average Exercise Price, Options Exercisable (in dollars per share)	$ 5.48
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) | shares	578,573
Weighted-Average Remaining Contractual Life	2 years 3 months 25 days
Weighted-Average Exercise Price (in dollars per share)	$ 2.42
Number of Options Exercisable (in shares) | shares	578,573
Weighted-Average Exercise Price, Options Exercisable (in dollars per share)	$ 2.42
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) | shares	125,000
Weighted-Average Remaining Contractual Life	2 years 10 months 10 days
Weighted-Average Exercise Price (in dollars per share)	$ 3.00
Number of Options Exercisable (in shares) | 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) | shares	6,496,899
Weighted-Average Remaining Contractual Life	7 months 17 days
Weighted-Average Exercise Price (in dollars per share)	$ 4.47
Number of Options Exercisable (in shares) | 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) | shares	25,000
Weighted-Average Remaining Contractual Life	8 years 2 months 16 days
Weighted-Average Exercise Price (in dollars per share)	$ 5.60
Number of Options Exercisable (in shares) | shares	25,000
Weighted-Average Exercise Price, Options Exercisable (in dollars per share)	$ 5.60