Retirement Plan - Additional Information (Detail) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Compensation and Retirement Disclosure [Abstract]
Retirement benefits plan, liability	$ 1,900,000		$ 1,900,000		$ 2,102,000
Retirement benefits plan, expense	$ 31,000	$ 55,000	$ 92,000	$ 164,000