Stock-Based Compensation (Details) (USD $)	3 Months Ended		9 Months Ended			1 Months Ended		9 Months Ended
	Sep. 30, 2012 Stock option	Sep. 30, 2011 Stock option	Sep. 30, 2012 Stock option	Sep. 30, 2011 Stock option	Sep. 30, 2012 Restricted stock awards	Jan. 31, 2012 2006 Stock Plan	Sep. 30, 2012 2006 Stock Plan	Sep. 30, 2012 2006 Stock Plan Stock option	Sep. 30, 2012 2006 Stock Plan Restricted stock awards
Stock-Based Compensation
Shares reserved for issuance							7,700,000
Number of shares reserved for issuance before annual increase						6,400,000
Annual increase in number of shares reserved for issuance						1,300,000
Percentage of outstanding shares of common stock used to compute annual increase in number of shares reserved for issuance						5.00%
Expiration period								10 years
Vesting period								4 years
Shares available for future issuance							1,954,674
Shares
Outstanding at the beginning of the period (in shares)			5,821,073						58,936
Options granted (in shares)			1,736,256
Options exercised (in shares)			(269,344)
Options cancelled (in shares)			(1,280,862)
Outstanding at the end of the period (in shares)	6,007,123		6,007,123						58,936
Exercisable at the end of the period (in shares)	3,502,865		3,502,865
Weighted average exercise price
Outstanding at the beginning of the period (in dollars per share)			$ 7.54
Options granted (in dollars per share)			$ 5.05
Options exercised (in dollars per share)			$ 3.35
Options cancelled (in dollars per share)			$ 8.83
Outstanding at the end of the period (in dollars per share)	$ 6.73		$ 6.73
Exercisable at the end of the period (in dollars per share)	$ 7.96		$ 7.96
Additional disclosures
Weighted-average grant date fair value of options (in dollars per share)	$ 6.00	$ 3.93	$ 4.04	$ 4.27
Shares
Outstanding at the beginning of the period (in shares)					82,450
Vested (in shares)					(68,757)
Granted (in shares)					45,243
Outstanding at the end of the period (in shares)					58,936
Weighted average grant date fair value
Outstanding at the beginning of the period (in dollars per share)					$ 4.94
Vested (in dollars per share)					$ 5.27
Granted (in dollars per share)					$ 5.47
Outstanding at the end of the period (in dollars per share)					$ 4.95
Weighted average assumptions used to estimate fair value of each employee stock option award
Risk-free interest rate (as a percent)	0.92%	2.05%	1.11%	2.49%
Expected life in years	6 years 2 months 23 days	6 years 3 months	6 years 2 months 26 days	6 years 3 months
Volatility (as a percent)	102.00%	100.00%	101.00%	101.00%