Net Loss Per Share (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Numerator:
Net loss	$ (23,548)	$ (9,144)
Denominator:
Weighted-average common shares outstanding	47,249	35,629
Basic and diluted net loss per share	$ (0.50)	$ (0.26)
Outstanding securities at period end not included in the computation of diluted net loss per share as they had an anti-dilutive effect:
Outstanding securities not included in the computation of diluted net loss per share	7,434	6,873
Restricted stock units and options to purchase common stock
Outstanding securities at period end not included in the computation of diluted net loss per share as they had an anti-dilutive effect:
Outstanding securities not included in the computation of diluted net loss per share	7,151	6,568
Warrants outstanding
Outstanding securities at period end not included in the computation of diluted net loss per share as they had an anti-dilutive effect:
Outstanding securities not included in the computation of diluted net loss per share	283	305