Computation of Basic and Diluted Net Loss per Share (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Numerator:
Net loss	$ (6,779)	$ (8,284)	$ (19,367)	$ (20,524)
Denominator:
Weighted average shares used to compute basic and diluted net loss per share	31,790	30,780	31,701	30,677
Basic and diluted net loss per share	$ (0.21)	$ (0.27)	$ (0.61)	$ (0.67)