Loans (Composition of Total Loans Outstanding) (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Jun. 30, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Dec. 31, 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	$ 923,949		$ 934,971
Less allowance for credit losses	(6,853)	$ (6,672)	(6,675)	$ (6,559)	$ (6,188)	$ (5,843)
Net loans	917,096		928,296
Residential Mortgage [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	93,586		99,932
Less allowance for credit losses	(123)	(133)	(161)	(163)	(207)	(221)
Commercial Mortgage [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	527,680		535,735
Less allowance for credit losses	(3,675)	(3,579)	(3,647)	(3,289)	(3,076)	(2,856)
Commercial Term [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	174,445		166,335
Less allowance for credit losses	(1,246)	(1,144)	(1,062)	(987)	(889)	(845)
Commercial Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	75,573		76,302
Less allowance for credit losses	(994)	(1,032)	(1,032)	(1,068)	(1,355)	(1,128)
Consumer: Home Equity [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	48,094		51,536
Less allowance for credit losses	(206)	(209)	(190)	(196)	(196)	(183)
Consumer: Other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	4,571		5,131
Less allowance for credit losses	$ (46)	$ (39)	$ (46)	$ (48)	$ (49)	$ (63)

DNB FINANCIAL CORP /PA/ 10-Q