Stock Based Compensation - Additional Information (Detail) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock option expense	$ 81,000	$ 113,000	$ 117,000	$ 149,000
Amortization of non-vested stock grants	$ 1,579,000	$ 1,129,000	$ 3,191,000	$ 2,322,000
Stock options exercised by employees and directors	5,500	7,500	15,000	9,000
Number of shares of non-vested stock that vested	5,995	7,720	11,229	17,600