Retirement Plan - Additional Information (Detail) (USD $)	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014
Compensation and Retirement Disclosure [Abstract]
Retirement benefits plan, liability	$ 2,101,000		$ 2,102,000
Retirement benefits plan, expense	$ 31,000	$ 55,000