Stock Award Plans and Stock Based Compensation (Details) (USD $)	12 Months Ended					12 Months Ended																12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2013 Restricted stock and restricted stock units	Dec. 31, 2013 Restricted stock and restricted stock units Maximum	Dec. 31, 2013 Stock Options	Dec. 31, 2012 Stock Options	Dec. 31, 2011 Stock Options	Dec. 31, 2012 Stock Options Minimum	Dec. 31, 2012 Stock Options Maximum	Dec. 31, 2013 Stock Options Employees	Dec. 31, 2013 Stock Options Board of Directors (nonemployees)	Dec. 31, 2013 Restricted stock	Dec. 31, 2013 2000 Stock Plan	Dec. 31, 2013 2000 Stock Plan Stock Options	Dec. 31, 2013 Employee stock purchase plan	Dec. 31, 2012 Employee stock purchase plan	Dec. 31, 2011 Employee stock purchase plan	Dec. 31, 2013 Employee stock purchase plan Maximum	Dec. 31, 2013 2012 Equity Incentive Plan	May 02, 2012 2012 Equity Incentive Plan	Dec. 31, 2013 2012 Equity Incentive Plan Stock Options Maximum	Dec. 31, 2012 2012 Equity Incentive Plan Restricted stock	Dec. 31, 2011 2012 Equity Incentive Plan Restricted stock	Dec. 31, 2010 2012 Equity Incentive Plan Restricted stock
Stock award plans and stock-based compensation
Awards granted (in shares)														0
Number of shares of common stock originally reserved for future grant																					7,100,000
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Expiration period															10 years							7 years
Vesting period											4 years	6 months
Period after termination to exercise awards that were vested											90 days
Period after termination to retiring employees to exercise vested awards											1 year
Number of shares of common stock available for future grant														0		1,800,000				3,600,000
Employee Stock Purchase Plan
Payroll deductions as a percentage of employee's salary																			10.00%
Purchase price as a percentage of the market value of a common stock on the day the stock is purchased																85.00%
Offering period over which compensation expense is amortized																6 months
Number of shares purchased under the plan																200,000	300,000	400,000
Estimated weighted-average assumptions
Weighted-average expected volatility (as a percent)						98.10%		97.80%	97.80%	113.55%
Weighted-average expected term						4 years 8 months 12 days		6 years 1 month 6 days	3 years 9 months 18 days	6 years 1 month 6 days										7 years
Risk-free interest rate, minimum (as a percent)						0.70%	0.45%	1.10%
Risk-free interest rate, maximum (as a percent)						1.40%	1.37%	2.40%
Expected dividend yield (as a percent)						0.00%	0.00%	0.00%
Stock-Based Compensation Expense
Forfeiture rate (as a percent)	5.00%	5.00%	5.00%
Stock-based compensation expense (in dollars)	$ 4,300,000	$ 3,900,000	$ 4,700,000													$ 100,000	$ 100,000	$ 100,000
Options
Outstanding at the beginning of the period (in shares)						21,260,000
Granted (in shares)						5,409,000
Exercised (in shares)						(1,511,000)
Canceled (in shares)						(1,138,000)
Expired (in shares)						(1,721,000)
Outstanding at the end of the period (in shares)						22,299,000	21,260,000
Vested and exercisable (in shares)						12,075,000
Options Vested or Expected to Vest at the end of the period (in shares)						21,515,000
Weighted Average Exercise Price
Outstanding at the beginning of the period (in dollars per share)						$ 2.24
Granted (in dollars per share)						$ 1.95
Exercised (in dollars per share)						$ 1.10
Canceled (in dollars per share)						$ 1.39
Expired (in dollars per share)						$ 7.26
Outstanding at the end of the period (in dollars per share)						$ 1.89	$ 2.24
Exercisable at the end of the period (in dollars per share)						$ 2.10
Options Vested or Expected to Vest at the end of the period (in dollars per share)						$ 1.89
Weighted Average Remaining Contractual Term
Outstanding at the end of the period						5 years 11 months 12 days
Exercisable at the end of the period						5 years 6 months 11 days
Options Vested or Expected to Vest at the end of the period						6 years 7 days
Aggregate Intrinsic Value
Outstanding at the end of the period (in dollars)						21,017,000
Exercisable at the end of the period (in dollars)						12,705,000
Options Vested or Expected to Vest at the end of the period (in dollars)						12,609,000
Additional disclosure
Total intrinsic value of options exercised (in dollars)						1,400,000	900,000	700,000
Total fair value of stock options vested (in dollars)						3,800,000	4,100,000	3,300,000
Total forfeiture adjusted unrecognized compensation cost (in dollars)						$ 9,400,000
Weighted-average period over which unrecognized compensation cost is expected to be recognized						2 years 10 months 24 days
Shares/units
Outstanding at the beginning of the period (in shares)				961,000	100,000
Granted (in shares)				195,000									0										0	0	0
Vested (in shares)				(231,000)									0
Forfeited (in shares)				(902,000)
Outstanding at the end of the period (in shares)				23,000	100,000
Weighted-Average Grant Date Fair Value per Share
Outstanding at the beginning of the period (in dollars per share)				$ 1.73
Granted (in dollars per share)				$ 1.27
Vested (in dollars per share)				$ 1.56
Forfeited (in dollars per share)				$ 1.68
Outstanding at the end of the period (in dollars per share)				$ 1.39