Commitments, Contingent Liabilities and Off-Balance Sheet Risk (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Loss Contingencies [Line Items]
Commitments and contingent liabilities outstanding
Assets held by DNB First Wealth Management in a fiduciary, custody or agency capacity	253,300
Federal Reserve Bank Of Philadelphia [Member]
Loss Contingencies [Line Items]
Line of credit facility maximum borrowing capacity	568,600
Stand-by Letters of Credit [Member]
Loss Contingencies [Line Items]
Commitments and contingent liabilities outstanding	2,300	4,600
Unfunded Loan And Lines Of Credit Commitments [Member]
Loss Contingencies [Line Items]
Commitments and contingent liabilities outstanding	190,800	176,600
Unfunded Loan And Lines Of Credit Commitments [Member] | Variable Rate [Member]
Loss Contingencies [Line Items]
Commitments and contingent liabilities outstanding	166,200	164,900
Unfunded Loan And Lines Of Credit Commitments [Member] | Fixed Rate [Member]
Loss Contingencies [Line Items]
Commitments and contingent liabilities outstanding	24,600	$ 11,600
Reserve for Unfunded Loan Commitments [Member]
Loss Contingencies [Line Items]
Commitments and contingent liabilities outstanding	$ 395		$ 348