Stock Options and Restricted Stock - Additional Information (Detail) (USD $)	9 Months Ended
	Sep. 30, 2014 Incentive_Plan	Sep. 30, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of equity incentive plans	3
Market value of restricted shares granted	$ 400,000
Stock options exercised, Shares	204,667	173,300
Proceeds from stock option exercises	1,820,000	1,597,000
Share-based compensation expense	$ 1,000,000	$ 1,000,000
Restricted Stock Units (RSUs) [Member] | Non-Employee Directors [Member] | 2010 Restricted Stock Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted common stock granted	4,866
Restricted Stock Units (RSUs) [Member] | Executive Officers [Member] | 2012 Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted common stock granted	4,312