Acquisitions - Additional Information (Detail) - USD ($)		3 Months Ended	12 Months Ended
	Jul. 01, 2015	Mar. 31, 2016	Dec. 31, 2015
Business Acquisition [Line Items]
Common stock, shares outstanding		11,983,313	11,939,887
Acquisition of goodwill		$ 49,600,000	$ 49,600,000
Peoples Bancorp Inc [Member]
Business Acquisition [Line Items]
Exchange ratio per share	95.00%
Share of common stock outstanding per share	$ 9.75
Common stock, shares outstanding	2,311,858
Common stock issued		2,192,202
Market closing price per share	$ 25.32
Total estimated purchase price	$ 78,147,000
Costs related to the acquisition			$ 4,900,000
Net intangible assets acquired	4,394,000
Acquisition of goodwill	21,424,000
Purchase price of the business assets, portion deductible	0
Core deposit intangible amortization period		7 years
Loan portfolio acquired	228,600,000
Discount on loan portfolio acquired	4,800,000
Performing portion of the loan portfolio acquired	223,400,000
Estimated fair value of performing portion of the loan portfolio	$ 220,000,000
Operating revenue, net of tax		$ 657,000
Non-recurring expense, net of tax		$ 95,000
Peoples Bancorp Inc [Member] | Maximum [Member]
Business Acquisition [Line Items]
Share of common stock outstanding per share	$ 33.14
Number of shares owned	100