Acquisitions - Pro Forma Result of Comparable Prior Reporting Period (Detail) - Peoples Bancorp Inc [Member] - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Business Acquisition [Line Items]
Net Interest Income	$ 19,774	$ 19,865
Provision for Loan Losses	532	644
Net Interest Income after Provision for Loan Losses	19,242	19,221
Non-interest Income	7,864	7,966
Non-Interest Expense	19,747	19,270
Income before Income Taxes	7,359	7,917
Income Tax Expense	1,978	1,939
Net Income	5,381	5,978
Net Income Available to Common Shareholders	$ 5,339	$ 5,984
Basic Earnings Per Share	$ 0.45	$ 0.52
Diluted Earnings Per Share	$ 0.44	$ 0.51