MERGERS AND ACQUISITIONS AND BRANCH CONSOLIDATIONS - Narrative (Details) $ / shares in Units, ft² in Thousands			3 Months Ended	12 Months Ended
	May 01, 2019 USD ($) shares	Oct. 01, 2018 USD ($) shares	Dec. 31, 2019 USD ($)	Dec. 31, 2019 USD ($) shares	Dec. 31, 2018 USD ($) shares	Dec. 31, 2017 USD ($)	Oct. 31, 2019 ft² bank	Apr. 30, 2019 $ / shares	Sep. 28, 2018 $ / shares
Business Acquisition [Line Items]
Shares of common stock issued for acquisition (in shares) | shares				1,765,704	1,052,635
Closing stock price per share (in shares) | $ / shares								$ 20.74	$ 23.80
Goodwill			$ 19,925,000	$ 19,925,000	$ 12,592,000	$ 719,000
Unaudited pro forma net income				20,900,000	12,200,000
Pro forma revenue				102,500,000	95,300,000
Merger related expenses				8,964,000	3,197,000	$ 0
Consolidation of operations expenses			988,000
Fixed asset writedowns			762,000
Lease termination costs			126,000
Severance and other			100,000
Assets Held-for-sale			$ 4,900,000	4,900,000
Pennsylvania Branch Locations
Business Acquisition [Line Items]
Number Of Bank Branch Locations | bank							5
Area of Real Estate Property | ft²							50
Mercersburg Financial Corporation
Business Acquisition [Line Items]
Percentage of interests acquired		100.00%
Cash paid		$ 4,900,000
Consideration transferred		29,900,000
Total assets acquired		181,400,000
Loans acquired		141,100,000
Securities available for sale		7,400,000
Total liabilities assumed		163,400,000
Deposits		160,400,000
Goodwill		$ 11,900,000
Merger related expenses				280,000	2,900,000
Mercersburg Financial Corporation | Investment Banking, Legal And Consulting Fees
Business Acquisition [Line Items]
Merger related expenses				81,000	1,200,000
Mercersburg Financial Corporation | Information Systems
Business Acquisition [Line Items]
Merger related expenses				199,000	1,100,000
Mercersburg Financial Corporation | Other Expenses
Business Acquisition [Line Items]
Merger related expenses				0	617,000
Mercersburg Financial Corporation | Common Stock
Business Acquisition [Line Items]
Shares of common stock issued for acquisition (in shares) | shares		1,052,635
Hamilton Bancorp, Inc.
Business Acquisition [Line Items]
Percentage of interests acquired	100.00%
Cash paid	$ 14,197,000
Total assets acquired	500,177,000
Loans acquired	347,361,000
Securities available for sale	60,882,000
Total liabilities assumed	449,358,000
Deposits	388,246,000
Goodwill	7,333,000
Consideration paid	50,819,000
Assets acquired excluding goodwill	492,800,000
Core deposit intangibles	4,550,000
Merger related expenses				7,700,000	267,000
Hamilton Bancorp, Inc. | Investment Banking, Legal And Consulting Fees
Business Acquisition [Line Items]
Merger related expenses				1,900,000	254,000
Hamilton Bancorp, Inc. | Information Systems
Business Acquisition [Line Items]
Merger related expenses				3,700,000	0
Hamilton Bancorp, Inc. | Other Expenses
Business Acquisition [Line Items]
Merger related expenses				$ 2,200,000	$ 13,000
Hamilton Bancorp, Inc. | Core Deposit Intangibles
Business Acquisition [Line Items]
Core deposit intangibles	$ 4,600,000
Amortization Period	10 years
Hamilton Bancorp, Inc. | Common Stock
Business Acquisition [Line Items]
Shares of common stock issued for acquisition (in shares) | shares	1,765,704