Fair Value Measurement - Additional Information (Detail) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2013	Dec. 31, 2012
Fair Value Measurements Disclosure [Line Items]
Derivative instrument maximum maturity period			30 years
Fair value of the collateral dependent loans, net carrying amount	$ 4,900,000	$ 2,200,000	$ 4,900,000	$ 2,200,000	$ 4,100,000
Specific allowance for collateral dependent loans	450,000	808,000	450,000	808,000	792,000
Increase in provision for loan losses	21,000	307,000	460,000	2,600,000
Discount applied to appraisals for estimated selling costs percentage			10.00%
Mortgage servicing rights, fair amount	228,000	387,000	228,000	387,000	0
Valuation allowance			2,000	676,000
Mortgage servicing rights, Outstanding Amount		391,000		391,000
Mortgage servicing rights net recovery/charge	4,000	4,000	4,000	4,000	680,000	680,000
Other real estate owned carried at fair value	6,300,000	6,400,000	6,300,000	6,400,000	4,200,000
Valuation allowance related to other real estate owned	3,500,000	6,700,000	3,500,000	6,700,000	4,100,000
Additional expenses related to other real estate owned	140,000	464,000	578,000	1,800,000
Maximum maturity period of short term borrowings			90 days
Minimum [Member]
Fair Value Measurements Disclosure [Line Items]
Increase in fair value	$ 250,000		$ 250,000