Stock Benefit Plans and Stock-Based Compensation - Summary of Stock Option Activity (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Shares Outstanding, Beginning balance	7,761
Shares, Granted	2,019
Shares, Exercised	(21)
Shares, Forfeited	(1,492)
Shares Outstanding, Ending balance	8,267	7,761
Shares, Options vested and exercisable	4,149
Shares, Options vested and expected to vest	7,819
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract]
Weighted average exercise price, Outstanding, Beginning balance	$ 2.23
Weighted average exercise price, Granted	$ 1.42
Weighted average exercise price, Exercised	$ 1.33
Weighted average exercise price, Forfeited	$ 1.99
Weighted average exercise price, Outstanding, Ending balance	$ 2.08	$ 2.23
Weighted average exercise price, Options vested and exercisable	$ 2.46
Weighted average exercise price, Options vested and expected to vest	$ 2.11
Weighted average remaining contractual term (in years), Outstanding, balance	7 years 4 months 6 days	7 years 7 months 2 days
Options vested and exercisable at December 31, 2014, Weighted average remaining contractual term (in years)	6 years 1 month 27 days
Options vested and expected to vest at December 31, 2014, Weighted average remaining contractual term (in years)	7 years 3 months 3 days
Aggregate intrinsic value, Outstanding, Beginning balance	$ 753
Aggregate intrinsic value, Granted	0
Aggregate intrinsic value, Exercised	0
Aggregate intrinsic value, Forfeited	0
Aggregate intrinsic value, Outstanding, Ending balance	71	753
Aggregate intrinsic value, Options vested and exercisable	27
Aggregate intrinsic value, Options vested and expected to vest	$ 64