Basis of Presentation and Nature of Operations (Details) $ in Thousands			3 Months Ended
	Jan. 11, 2020 bank	Jul. 01, 2017 bank	Mar. 31, 2020 USD ($) bank	Dec. 31, 2019 USD ($)	Mar. 31, 2019 USD ($)	Jan. 01, 2019 USD ($)
Business Acquisition [Line Items]
Number of community banking office locations, ACNB | bank			21
Right of use assets			$ 5,974	$ 3,502	$ 3,804
Lease liabilities			$ 6,047	$ 3,502	$ 3,804
Accounting Standards Update 2016-02
Business Acquisition [Line Items]
Right of use assets						$ 4,000
Lease liabilities						$ 4,000
New Windsor
Business Acquisition [Line Items]
Number of community banking office locations, acquired | bank		7
Frederick County Bancorp, Inc.
Business Acquisition [Line Items]
Number of community banking office locations, acquired | bank	5