Stockholders' Equity, Equity Incentive Plans and Warrants (Summary of Stock Option Activity) (Details) (USD $)	12 Months Ended
	Dec. 31, 2012
Number of shares
Options outstanding at beginning of period (in shares)	7,394,551
Options granted (in shares)	2,486,000
Options exercised (in shares)	(27,189)
Options forfeited (in shares)	(574,705)
Options expired (in shares)	(326,528)
Options outstanding at end of period (in shares)	8,952,129
Options vested and expected to vest (in shares)	8,560,457
Options exercisable (in shares)	5,622,274
Weighted average exercise price
Options outstanding at beginning of period, weighted average exercise price	$ 3.39
Options granted, weighted average exercise price	$ 1.36
Options exercised, weighted average exercise price	$ 0.83
Options forfeited, weighted average exercise price	$ 1.84
Options expired, weighted average exercise price	$ 3.53
Options vested and expected to vest, weighted average exercise price	$ 3.00
Options exercisable, weighted average exercise price	$ 3.67
Options outstanding at end of period, weighted average exercise price	$ 2.93
Options outstanding, weighted average remaining contractual term	4 years 6 months 22 days
Options outstanding, aggregate intrinsic value	$ 28,380
Options vested and expected to vest, weighted average remaining contractual term	4 years 5 months 9 days
Options vested and expected to vest, aggregate intrinsic value	24,990
Options exercisable, weighted average remaining contractual term	3 years 9 months 7 days
Options exercisable, aggregate intrinsic value	$ 9,312