Goodwill and Other Intangible Assets (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Feb. 28, 2022	Dec. 31, 2021	Mar. 31, 2021	Jan. 11, 2020	Jul. 01, 2017	Jan. 05, 2005
Finite-Lived Intangible Assets [Line Items]
Goodwill	$ 44,184		$ 42,108	$ 42,108
ACNB Insurance Services, Inc.
Finite-Lived Intangible Assets [Line Items]
Goodwill							$ 6,308
New Windsor
Finite-Lived Intangible Assets [Line Items]
Goodwill						$ 13,272
Frederick County Bancorp, Inc.
Finite-Lived Intangible Assets [Line Items]
Goodwill					$ 22,528
Hockley & O'Donnell Insurance Agency, LLC
Finite-Lived Intangible Assets [Line Items]
Goodwill		$ 2,077
Core Deposit Intangibles
Finite-Lived Intangible Assets [Line Items]
Amortization period	10 years
Core Deposit Intangibles | New Windsor
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount of intangible asset	$ 2,418					$ 2,418
Accumulated amortization of intangible asset	1,692
Core Deposit Intangibles | Frederick County Bancorp, Inc.
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount of intangible asset	3,560				$ 3,560
Accumulated amortization of intangible asset	1,359
Customer Lists | ACNB Insurance Services, Inc.
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount of intangible asset	16,151
Accumulated amortization of intangible asset	$ 7,562
Customer Lists | Minimum
Finite-Lived Intangible Assets [Line Items]
Amortization period	8 years
Customer Lists | Maximum
Finite-Lived Intangible Assets [Line Items]
Amortization period	15 years
Covenant Not To Compete | Hockley & O'Donnell Insurance Agency, LLC
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount of intangible asset		$ 5,835