Retirement Plans and Deferred Compensation - Additional Information (Detail) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Deferred Compensation Arrangement with Individual, Postretirement Benefits [Line Items]
Costs incurred under defined contribution pension plan	$ 126,000	$ 114,000	$ 397,000	$ 430,000
Amount charged to expense in connection with agreements for supplemental retirement benefits	$ 102,000	$ 88,000	$ 18,000	$ 239,000
Minimum [Member]
Deferred Compensation Arrangement with Individual, Postretirement Benefits [Line Items]
Discount rates for supplemental retirement benefits plans			8.00%
Maximum [Member]
Deferred Compensation Arrangement with Individual, Postretirement Benefits [Line Items]
Discount rates for supplemental retirement benefits plans			12.00%