Organization, Basis of Presentation and Summary of Significant Accounting Policies - Net Income (Loss) Per Share (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Numerator:
Net loss available to common stockholders	$ 205	$ (1,142)	$ (5,695)	$ (5,167)	$ (1,502)	$ (13,049)	$ (7,244)	$ (6,158)	$ (11,799)	$ (27,953)	$ (25,463)
Denominator:
Weighted average shares outstanding - basic	45,053	41,225	38,518	37,714	37,027	37,036	37,247	36,614	40,649	36,982	35,849
Potential common shares - options (treasury stock method)									0	0	0
Weighted average shares outstanding - diluted	45,053	41,225	38,518	37,714	37,027	37,036	37,247	36,614	40,649	36,982	35,849
Shares excluded (anti-dilutive)									150	2	174
Shares excluded due to an exercise price greater than weighted average stock price for the period									1,511	2,150	1,453
Net loss per common share:
Basic	$ 0.00	$ (0.03)	$ (0.15)	$ (0.14)	$ (0.04)	$ (0.35)	$ (0.19)	$ (0.17)	$ (0.29)	$ (0.76)	$ (0.71)
Diluted	$ 0.00	$ (0.03)	$ (0.15)	$ (0.14)	$ (0.04)	$ (0.35)	$ (0.19)	$ (0.17)	$ (0.29)	$ (0.76)	$ (0.71)