Share-Based Compensation - Additional Information (Detail) - USD ($) $ in Thousands	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]
Share-based compensation expense	$ 494	$ 447	$ 1,022	$ 1,051
Related tax benefits on non-qualified stock options	$ 161	$ 149	$ 337	$ 368
Number of shares, stock options exercised	6,874	18,500	26,455	33,695