Net Loss Per Share Computation of Basic and Diluted Net Loss Per Share (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Numerator:
Net loss	$ (6,236)	$ (10,406)
Denominator:
Weighted average number of common shares outstanding	42,205	41,149
Net loss per share, basic and diluted	$ (0.15)	$ (0.25)