Summary of Stock Option Activity (Detail) (USD $)	3 Months Ended
	Mar. 31, 2014
Weighted Average Exercise Price
Granted
Exercised
Directors Stock Option Plan
Number of Shares
Beginning Balance	103,500
Granted
Exercised
Ending Balance	103,500
Weighted Average Exercise Price
Beginning Balance	$ 21.30
Granted
Exercised
Ending Balance	$ 21.30
Employee Stock Option Plan
Number of Shares
Beginning Balance	82,000
Granted
Exercised
Expired	(28,500)
Ending Balance	53,500
Weighted Average Exercise Price
Beginning Balance	$ 22.06
Granted
Exercised
Expired	$ 21.85
Ending Balance	$ 22.17
2013 Plan
Number of Shares
Granted
Exercised