Stock Based Compensation (Details) (USD $)	3 Months Ended			3 Months Ended			3 Months Ended					3 Months Ended																												3 Months Ended
	Mar. 31, 2014	Feb. 05, 2014	Oct. 15, 2013	Mar. 31, 2014 Employees [Member]	Mar. 31, 2013 Employees [Member]	Mar. 31, 2014 Employees and Directors [Member]	Mar. 31, 2014 Senior management [Member]	Mar. 31, 2013 Senior management [Member]	Mar. 31, 2014 Directors and nonemployees [Member]	Mar. 31, 2014 Stock Options [Member]	Dec. 31, 2013 Stock Options [Member]	Mar. 31, 2014 Stock Options [Member] Range $ 1.83 - 2.50 [Member]	Mar. 31, 2014 Stock Options [Member] Range $ 2.51 - 3.50 [Member]	Mar. 31, 2014 Stock Options [Member] Range $ 3.51 - 8.00 [Member]	Mar. 31, 2014 Stock Options [Member] Range $ 8.01 - 32.55 [Member]	Mar. 31, 2014 Stock Options [Member] Maximum [Member]	Mar. 31, 2014 Stock Options [Member] Employees [Member]	Mar. 31, 2013 Stock Options [Member] Employees [Member] Minimum [Member]	Mar. 31, 2013 Stock Options [Member] Employees [Member] Maximum [Member]	Mar. 31, 2014 Stock Options [Member] Non employees [Member]	Mar. 31, 2014 Stock Options And Warrants [Member]	Mar. 31, 2013 Stock Options And Warrants [Member]	Mar. 31, 2014 Stock Options And Warrants [Member] Employees [Member]	Mar. 31, 2013 Stock Options And Warrants [Member] Employees [Member]	Mar. 31, 2014 Stock Options And Warrants [Member] Non-Employees [Member]	Mar. 31, 2013 Stock Options And Warrants [Member] Non-Employees [Member]	Mar. 31, 2014 Stock Options And Warrants [Member] Research and Development Expense [Member] Employees [Member]	Mar. 31, 2013 Stock Options And Warrants [Member] Research and Development Expense [Member] Employees [Member]	Mar. 31, 2014 Stock Options And Warrants [Member] Research and Development Expense [Member] Non-Employees [Member]	Mar. 31, 2013 Stock Options And Warrants [Member] Research and Development Expense [Member] Non-Employees [Member]	Mar. 31, 2014 Stock Options And Warrants [Member] General and Administrative Expense [Member] Employees [Member]	Mar. 31, 2013 Stock Options And Warrants [Member] General and Administrative Expense [Member] Employees [Member]	Mar. 31, 2014 Stock Options And Warrants [Member] General and Administrative Expense [Member] Non-Employees [Member]	Mar. 31, 2013 Stock Options And Warrants [Member] General and Administrative Expense [Member] Non-Employees [Member]	Mar. 31, 2014 Stock Options And Warrants [Member] Minimum [Member]	Mar. 31, 2014 Stock Options And Warrants [Member] Maximum [Member]	Mar. 31, 2014 Restricted Stock [Member]	Mar. 31, 2013 Restricted Stock [Member]	Dec. 31, 2013 Restricted Stock [Member] Senior management [Member]	Mar. 31, 2014 2000 Long Term Incentive Plan [Member]	Mar. 31, 2014 2008 Stock Incentive Plan [Member]	Mar. 31, 2014 2008 Stock Incentive Plan [Member] Restricted Stock [Member] Senior management [Member]	Dec. 31, 2013 2008 Stock Incentive Plan [Member] Restricted Stock [Member] Senior management [Member]	Dec. 31, 2012 2008 Stock Incentive Plan [Member] Restricted Stock [Member] Senior management [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation, shares subject to stock options (in shares)																																								800,000	5,900,000
Expiration date																																								Aug. 06, 2010
Share-based compensation, shares available for future grant (in shares)																																								0	4,100,000
Share-based compensation arrangement by share-based payment award, fair value assumptions and methodology [Abstract]
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Method Used										Black-Scholes option-pricing model
Risk-free interest rate (in hundredths)																					1.98%	1.16%
Expected volatility (in hundredths)																		85.40%	85.80%																87.80%	89.60%
Expected lives																10 years						6 years													6 years	10 years
Expected dividend yield (in hundredths)																					0.00%	0.00%
Estimated annualized forfeiture rate (in hundredths)				12.00%	13.00%		2.00%	3.00%	0.00%
Unrecognized compensation expense related to unvested stock options, granted						$ 4,600,000
Unrecognized compensation cost, recognized as expense over a weighted-average period	1 year 2 months 26 days
Number of Options (Employees and Non-Employees) [Abstract]
Outstanding at beginning of period (in shares)	100,000									6,395,736							6,228,593			167,143																			100,000					100,000
Granted (in shares)										270,000							270,000
Outstanding at end of period (in shares)										6,665,736							6,498,593			167,143																			100,000					100,000
Options exercisable at end of period (in shares)										3,573,404							3,406,261			167,143
Weighted-Average Exercise Price Options [Abstract]
Outstanding at beginning of period (in dollars per share)										$ 3.11
Granted (in dollars per share)										$ 5.38
Outstanding at end of period (in dollars per share)										$ 3.20
Options exercisable at end of period (in dollars per share)										$ 3.74
Number of Unvested Stock Options (Employees and Non-Employees) [Abstract]
Non-vested at beginning of period (in shares)										3,102,873							3,102,873			0
Granted, unvested stock options (in shares)										270,000							270,000			0
Vested (in shares)										(280,541)							(280,541)			0
Non-vested at end of period (in shares)										3,092,332							3,092,332			0
Weighted average grant date fair value per share [Abstract]
Non-vested at beginning of period (in dollars per share)										$ 1.66
Granted, unvested stock options (in dollars per share)										$ 3.97
Vested (in dollars per share)										$ 1.68
Non-vested at end of period (in dollars per share)										$ 1.86
Expected to vest (in shares)																																										50,000
Expected to vest over subsequent period (in shares)																																										50,000
Value of restricted shares issued																																											627,000	186,900
Total stock-based compensation expense resulting from stock options and warrants [Abstract]
Allocated employee and non-employee stock-based compensation expense, Total																							487,113	234,812	278,531	27,212	175,153	50,172	86,539	0	311,960	184,640	191,992	27,212			154,578	45,984
Share-based compensation arrangement by share-based payment award, shares issued in period (in shares)										270,000											25,000
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	$ 2.51	$ 3.51	$ 8.01
Range of Exercise Prices, Upper Range (in dollars per share)												$ 2.50	$ 3.50	$ 8.00	$ 32.55
Number of Options (in shares)										6,665,736		5,130,056	194,482	962,701	378,497
Weighted-Average Remaining Contractual Life										8 years 4 months 28 days		9 years 2 months 16 days	6 years 8 months 8 days	6 years 8 months 8 days	2 years 10 months 17 days
Weighted-Average Exercise Price (in dollars per share)										$ 3.20		$ 2.21	$ 2.79	$ 6.31	$ 8.86
Number of Options Exercisable (in shares)										3,573,404		2,374,550	153,291	667,066	378,497
Weighted-Average Remaining Contractual Life										8 years 4 months 28 days		9 years 2 months 16 days	6 years 8 months 8 days	6 years 8 months 8 days	2 years 10 months 17 days
Weighted-Average Exercise Price, Options Exercisable (in dollars per share)										$ 3.74		$ 2.15	$ 2.69	$ 6.75	$ 8.86
The aggregate intrinsic value of outstanding options										$ 11,880,000
Closing price of the common stock (in dollars per share)		$ 6.50	$ 2.25							$ 3.49											$ 5.60
Warrants outstanding (in shares)	7,894,791										8,324,609