Summary of Information Regarding Option Activity (Detail) (USD $)	6 Months Ended
	Jun. 30, 2012		Jun. 30, 2011
Options Outstanding
Options outstanding at January 1, 2012	2,823,400		2,573,800
Granted	94,190
Exercised	(217,500)
Forfeited/Cancelled	(70,600)
Options outstanding at June 30, 2012	2,629,490		2,573,800
Options exercisable at June 30, 2012	1,678,700
Vested and expected to vest at June 30, 2012	2,506,271	[1]
Weighted average exercise price per share
Options outstanding at January 1, 2012	$ 4.05		$ 4.14
Granted	$ 1.89
Exercised	$ 2.65
Forfeited/Cancelled	$ 4.31
Options outstanding at June 30, 2012	$ 4.08		$ 4.14
Options exercisable at June 30, 2012	$ 4.34
Vested and expected to vest at June 30, 2012	$ 4.09	[1]
Weighted average remaining contractual term (in years)
Options outstanding at June 30, 2012	5 years 11 months 12 days
Options exercisable at June 30, 2012	4 years 7 months 10 days
Vested and expected to vest at June 30, 2012	5 years 10 months 6 days	[1]
Aggregate intrinsic value
Options outstanding at June 30, 2012	$ 1,713,058
Options exercisable at June 30, 2012	926,194
Vested and expected to vest at June 30, 2012	$ 1,647,742	[1]

[1] This represents the number of vested options as of June 30, 2012 plus the number of unvested options expected to vest as of June 30, 2012 based on the unvested outstanding options at June 30, 2012 adjusted for estimated forfeiture rates of 8% for awards granted to non-executive level employees and 3% for awards granted to executive level employees.