Summary of Significant Accounting Policies (Details)				3 Months Ended	12 Months Ended
	May 01, 2018 USD ($) payment	Dec. 15, 2017 USD ($) branch shares	May 24, 2017 USD ($) payment	Jun. 30, 2018 payment	Dec. 31, 2018 USD ($) banking_location trust office location	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Business Acquisition [Line Items]
Number of banking locations | banking_location					43
Number of wealth offices | office					6
Number of insurance and risk management locations | location					2
Number of trusts acquired | trust					2
Cash reserve deposit required and made					$ 4,300,000	$ 5,800,000
Other than temporary impairment losses					$ 0	0	$ 0
Delinquency period after which the accrual of Interest Is generally discontinued					90 days
Delinquency period after which a lease Is charged off					120 days
Federal home loan bank stock					$ 14,530,000	$ 20,083,000
Federal reserve bank stock					$ 12,000,000
Domenick
Business Acquisition [Line Items]
Value of consideration	$ 1,456,000
Number of contingent cash payments | payment	3
Maximum contingent cash payment amount per period	$ 250,000
Cash paid at closing	$ 750,000
RBPI
Business Acquisition [Line Items]
Value of consideration		$ 138,740,000
Number of shares issued | shares		3,101,316
Number of securities called by warrants | shares		140,224
Warrants to purchase BMTC common stock value		$ 1,900,000
Cash-out of certain options		112,000
Cash in lieu of fractional shares		7,000
Loans assumed		570,400,000
Investment securities available for sale		121,587,000
Deposits		$ 593,172,000
Number of branches acquired | branch		12
Hirshorn
Business Acquisition [Line Items]
Value of consideration			$ 7,460,000
Number of contingent cash payments | payment			2
Cash paid at closing			$ 5,770,000
Number of contingent cash payments made | payment				1
Contingent cash payments, maximum payment of each installment			$ 575,000