Stock-Based Compensation (Details) (Service-based stock options, USD $)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012
Stock-Based Compensation
Vesting period			4 years
Expiration period			10 years
Weighted average grant-date fair value (in dollars per share)			$ 0.70	$ 1.25
Net compensation expense related to employees and directors (in dollars)	$ 145,000	$ 1,127,000	$ 528,000	$ 3,166,000
Forfeiture adjustments included in compensation costs due to restructuring activities (in dollars)			1,125,000
Weighted average assumptions used to estimate fair value of each service-based stock option grant
Expected dividend rate (as a percent)			0.00%	0.00%
Options
Outstanding at the beginning of the period (in shares)			9,987,468
Granted (in shares)			1,515,000
Expired (in shares)			(2,787,259)
Forfeited (in shares)			(2,275,186)
Outstanding at the end of the period (in shares)	6,440,023		6,440,023		9,987,468
Exercisable at the end of the period (in shares)	2,982,001		2,982,001
Weighted Average Exercise Price
Outstanding at the beginning of the period (in dollars per share)			$ 2.38
Granted (in dollars per share)			$ 1.07
Expired (in dollars per share)			$ 2.64
Forfeited (in dollars per share)			$ 2.27
Outstanding at the end of the period (in dollars per share)	$ 1.99		$ 1.99		$ 2.38
Exercisable at the end of the period (in dollars per share)	$ 2.35		$ 2.35
Weighted Average Remaining Contractual Term
Outstanding at the beginning of the period			7 years 7 months 6 days		7 years 6 months
Outstanding at the end of the period			7 years 7 months 6 days		7 years 6 months
Exercisable at the end of the period			6 years 1 month 6 days
Additional disclosures
Total unrecognized compensation cost (in dollars)	2,155,000		2,155,000
Weighted average period over which unrecognized compensation is expected to be recognized			2 years 8 months 12 days
Total fair value of options vested (in dollars)			$ 1,861,000	$ 2,136,000
Minimum
Weighted average assumptions used to estimate fair value of each service-based stock option grant
Expected stock price volatility (as a percent)			74.00%	72.90%
Risk-free interest rate (as a percent)			0.10%	0.90%
Expected life			5 years	6 years
Maximum
Weighted average assumptions used to estimate fair value of each service-based stock option grant
Expected stock price volatility (as a percent)			87.90%	74.90%
Risk-free interest rate (as a percent)			2.10%	1.50%
Expected life			6 years 3 months 18 days	6 years 3 months 18 days
Non-employee
Stock-Based Compensation
Vesting period			1 year
Options
Granted (in shares)			285,000