Retirement Plans and Deferred Compensation - Additional Information (Detail) (USD $)	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Deferred Compensation Arrangement with Individual, Postretirement Benefits [Line Items]
Costs incurred under defined contribution pension plan	$ 139,000	$ 193,000
Amount charged to expenses in connection with agreements for supplemental benefits plans	$ 113,000	$ 64,000
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%