Net Loss Per Share (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Net Loss Per Share [Abstract]
Net loss	$ (10,040)	$ (7,760)
Weighted-average common shares outstanding (in shares)	35,199	28,674
Net loss per share - basic and diluted (in dollars per share)	$ (0.29)	$ (0.27)
Stock options and restricted stock units (in shares)	5,090	4,892