Share-Based Compensation - Additional Information (Detail) (USD $)	3 Months Ended		6 Months Ended			3 Months Ended	6 Months Ended			3 Months Ended	6 Months Ended	1 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012 Maximum	Jun. 30, 2012 Stock Options	Jun. 30, 2012 Stock Options	Jun. 30, 2012 Stock Options Minimum	Jun. 30, 2012 Stock Options Maximum	Jun. 30, 2012 Restricted Stock	Jun. 30, 2012 Restricted Stock	Apr. 30, 2012 Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock option term							10 years
Stock options vesting percentage							100.00%
Vested period								3 months	2 years		3 years
Percentage of average closing price to be paid by employees			85.00%
Common stock purchases through advance payroll deductions in a calendar year			$ 87,000		$ 25,000
Share-based compensation	360,000	350,000	686,000	718,000
Estimated pre-vesting forfeiture rate			4.77%
Unrecognized compensation expense						133,000	133,000			2,182,000	2,182,000
Unrecognized compensation expense expected recognition period						1 year 1 month 21 days				1 year 7 months 24 days
Weighted-average grant date fair value for stock options	$ 3.86
Grant date fair value of ESPP options												$ 45,400