Goodwill and Intangible Assets - Additional Information (Detail) - USD ($)			12 Months Ended
	Jul. 01, 2015	Apr. 03, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Intangible Assets [Line Items]
Goodwill acquired			$ 21,424,000	$ 8,428,000
Goodwill impairment loss			0	0
Amortization expense for intangible assets totaled			$ 988,000	$ 880,000	$ 760,000
Peoples Bancorp Inc [Member]
Intangible Assets [Line Items]
Goodwill acquired	$ 21,400,000
Core deposit intangible amortization period			7 years
Summit [Member]
Intangible Assets [Line Items]
Goodwill acquired		$ 8,400,000
Core deposit intangible amortization period			7 years
Core Deposits [Member] | Minimum [Member]
Intangible Assets [Line Items]
Core deposit intangible amortization period			7 years
Core Deposits [Member] | Maximum [Member]
Intangible Assets [Line Items]
Core deposit intangible amortization period			10 years