Stock-Based Compensation (Details) (USD $)	6 Months Ended	12 Months Ended
	Jun. 30, 2012	Dec. 31, 2011
Stock-Based Compensation
Maximum shares of common stock to be issued for grants (in shares)	7,400,000
Stock options
Shares
Options outstanding at the beginning of the period (in shares)	4,459,034
Granted (in shares)	31,000
Canceled (in shares)	(185,137)
Options outstanding at the end of the period (in shares)	4,304,897	4,459,034
Options vested and expected to vest at the end of the period (in shares)	4,271,786
Options exercisable at the end of the period (in shares)	2,923,338
Shares Available for Grant under the 2008 Plan (in shares)	4,449,646
Weighted Average Exercise Price Per Share
Options outstanding at the beginning of the period (in dollars per share)	$ 6.08
Granted (in dollars per share)	$ 3.99
Canceled (in dollars per share)	$ 8.50
Options outstanding at the end of the period (in dollars per share)	$ 5.96	$ 6.08
Options vested and expected to vest at the end of the period (in dollars per share)	$ 5.99
Options Exercisable at the end of the period (in dollars per share)	$ 7.04
Weighted Average Remaining Contractual Term (In Years)
Options outstanding at the beginning of the period	6 years 8 months 12 days	6 years 10 months 24 days
Options outstanding at the end of the period	6 years 8 months 12 days	6 years 10 months 24 days
Options vested and expected to vest at the end of the period	6 years 8 months 12 days
Options Exercisable at at the end of the period	5 years 9 months 18 days
Additional information on options
Weighted average grant-date fair value (in dollars per share)	$ 2.49
Restricted stock
Shares
Outstanding and unvested at the beginning of the period (in shares)	6,000
Granted (in shares)	12,000
Vested (in shares)	(6,000)
Outstanding and unvested at the end of the period (in shares)	12,000
Weighted Average Grant Date Fair Value (per share)
Outstanding and unvested at the beginning of the period (in dollars per share)	$ 3.24
Granted (in dollars per share)	$ 4.50
Vested (in dollars per share)	$ 3.24
Outstanding and unvested at the end of the period (in dollars per share)	$ 4.50