Loans - Additional Information (Detail)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2016 USD ($) Loans	Sep. 30, 2015 Loans	Sep. 30, 2016 USD ($) Loans	Sep. 30, 2015 Loans	Dec. 31, 2015 USD ($) Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Net unamortized loan fees | $	$ (824,000)		$ (824,000)		$ (636,000)
Percentage of comprised loan, commercial, industrial and agricultural loans	32.00%		32.00%		30.00%
Percentage of comprised loan, commercial mortgage loans	28.00%		28.00%		28.00%
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	36.00%		36.00%		36.00%
Number of Loans | Loans			15		16
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	1	0	1	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%