Summary of Significant Accounting Policies (Narrative) (Details) $ in Thousands		12 Months Ended
	Jan. 01, 2018 USD ($)	Dec. 31, 2017 USD ($) segment loan item	Dec. 31, 2016 USD ($) loan
Summary Of Significant Accounting Policies [Line Items]
Number of community offices, providing investment and trust services | item		15
Number of operating segments | segment		1
Collection of the original recorded investment on HTM securities (percentage)		85.00%
Impairment charges on securities		$ 0	$ 0
Restricted stock		$ 7,641	5,381
Accrual of interest general discontinued period, in days		90 days
General charge-off period, in days		120 days
Partial charge-off of loan amount		$ 1,325	$ 311
Number of TDR loans | loan		8	5
TDR recorded investment		$ 1,857	$ 914
Loan defaults on TDRs		0	0
Reserve for unfunded loan commitments		348	345
Unrecognized tax positions		$ 0
Age of eligibility for noncontributory defined benefit pension plan		21 years
Defined benefit pension plan requisite service period, in years		1 year
Highest consecutive years of average-compensation (years)		5 years
Defined benefit pension plan, years of service		10 years
Advertising and marketing		$ 755	707
Federal Home Loan Bank Of Pittsburgh [Member]
Summary Of Significant Accounting Policies [Line Items]
Restricted stock		5,200	4,100
Federal Reserve Bank Of Philadelphia [Member]
Summary Of Significant Accounting Policies [Line Items]
Restricted stock		2,300	1,100
Atlantic Central Bankers Bank [Member]
Summary Of Significant Accounting Policies [Line Items]
Restricted stock		156	156
Accounting Standards Update 2016-09 [Member]
Summary Of Significant Accounting Policies [Line Items]
Excess tax benefit from share-based compensation		$ 331
Accounting Standards Update 2018-02 [Member] | Subsequent Event [Member]
Summary Of Significant Accounting Policies [Line Items]
Reclassification amount from accumulated other comprehensive income related to Tax Cuts and jobs Act	$ 471
Commercial Mortgage [Member]
Summary Of Significant Accounting Policies [Line Items]
Number of TDR loans | loan		3
TDR recorded investment		$ 992
Real estate loans in process of foreclosure		416	3,100
Consumer Installment Loan [Member]
Summary Of Significant Accounting Policies [Line Items]
Partial charge-off of loan amount		$ 2	$ 2
Number of TDR loans | loan		1	1
Consumer: Home Equity [Member]
Summary Of Significant Accounting Policies [Line Items]
Number of TDR loans | loan			1
TDR recorded investment			$ 102
Accruing Loans [Member]
Summary Of Significant Accounting Policies [Line Items]
Number of TDR loans | loan		5
TDR recorded investment		$ 1,128
Nonaccrual Impaired Loans [Member]
Summary Of Significant Accounting Policies [Line Items]
Number of TDR loans | loan		3	4
TDR recorded investment		$ 729	$ 812
Residential Mortgage [Member]
Summary Of Significant Accounting Policies [Line Items]
Partial charge-off of loan amount		$ 151	$ 151
Number of TDR loans | loan		2	2