Stock-Based Compensation - Additional Information (Detail) (USD $)	3 Months Ended		12 Months Ended
	Mar. 31, 2012	Mar. 31, 2011	Dec. 31, 2010	Dec. 31, 2011
Compensation Related Costs Share Based Payments Disclosure [Line Items]
Stock options, expected dividend yield
Total amount of cash received from exercise of options	$ 100,000
Employee stock purchase plan, number of offering	2
Employee stock purchase plan, offering period	6 months
Compensation expense	1,442,000	858,000
Stock Options
Compensation Related Costs Share Based Payments Disclosure [Line Items]
Stock options, expected dividend yield	0.00%
Stock-based compensation, approximate forfeitures rate	3.00%
Compensation expense	700,000	500,000
Stock Options | Maximum
Compensation Related Costs Share Based Payments Disclosure [Line Items]
Stock options, contractual term	10 years
Performance-Based Restricted Stock
Compensation Related Costs Share Based Payments Disclosure [Line Items]
Restricted stock award program, measurement period			3 years
Restricted stock award program, awarded shares as a percentage of the original award amount, lower limit			0.00%
Restricted stock award program, awarded shares as a percentage of the original award amount, upper limit			200.00%
Restricted stock award program, payment of award as percentage of target				97.40%
Compensation expense	100,000	200,000
Time Based Restricted Stock
Compensation Related Costs Share Based Payments Disclosure [Line Items]
Compensation expense	500,000
Restricted stock award program, vesting period	3 years
Employee Stock Purchase Plan
Compensation Related Costs Share Based Payments Disclosure [Line Items]
Employee stock purchase plan, purchase price discount	15.00%
Compensation expense	$ 100,000	$ 100,000