Net Loss Per Share (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Earnings Per Share [Abstract]
Net loss	$ (12,405)	$ (10,040)
Weighted-average common shares outstanding (in shares)	37,034	35,199
Net loss per share - basic and diluted (in dollars per share)	$ (0.33)	$ (0.29)