Credit Quality Assessment (Additional Information) (Detail) - USD ($)	9 Months Ended	12 Months Ended
	Sep. 30, 2015	Dec. 31, 2014
Accounts, Notes, Loans and Financing Receivable [Line Items]
Restructured accruing	$ 2,300,000	$ 1,600,000
Other real estate owned	2,619,000	3,195,000
Restructured Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Specific allowance	400,000	100,000
Additional Financing Receivable Troubled Debt Restructurings Restructured	$ 500,000	$ 100,000