Summary of Significant Accounting Policies - Computation of Basic and Diluted Net Loss Per Share (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Accounting Policies [Abstract]
Net loss	$ (4,647)	$ (2,076)
Net loss allocable to unvested restricted shares	125	66
Undistributed net loss attributable to common shares	$ (4,522)	$ (2,010)
Weighted average shares outstanding - basic	28,146	27,584
Effects of dilutive securities:
Employee equity compensation plans
Weighted average shares outstanding - diluted	28,146	27,584
Basic net loss per share	$ (0.16)	$ (0.07)
Diluted net loss per share	$ (0.16)	$ (0.07)