Loans - Additional Information (Detail)	3 Months Ended	6 Months Ended		12 Months Ended
	Jun. 30, 2015 USD ($) Loans	Jun. 30, 2015 USD ($) Loans	Jun. 30, 2014 Loans	Dec. 31, 2014 USD ($) Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Net unamortized loan fees and costs	$ (165,000)	$ (165,000)		$ 483,000
Percentage of comprised loan, commercial, industrial and agricultural loans	31.00%	31.00%		32.00%
Percentage of comprised loan, commercial mortgage loans	28.00%	28.00%		26.00%
Risk rating to commercial loans	$ 250,000,000	$ 250,000,000
Percentage of loan-to-value to business equipment		80.00%
Percentage of loan-to-value to accounts receivable		75.00%
Percentage of loan-to-value to business inventory		60.00%
Percentage of loan-to-value to real estate		85.00%
Percentage of residential real estate loan in portfolio	38.00%	38.00%		37.00%
Number of Loans | Loans		15		15
Minimum period to be considered for loan to have defaulted		90 days
Principal balances forgiven in connection with loan restructuring	$ 0	$ 0		$ 0
Outstanding balance of semi annual loans		Greater than $1 million
Outstanding balance of annual loans		Less than $1 million
Trouble Debt Restructuring [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of Loans | Loans	0		0
Maximum [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Maximum percentage of consumer loan and credit card in portfolio	10.00%	10.00%		10.00%