Leases (Analysis of Leased Property under Finance Leases) (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Leases [Abstract]
Equipment	$ 397	$ 375
Less accumulated depreciation and amortization	(117)	(42)
Leased property under finance leases, net	$ 280	$ 333

Finance Lease, Leased Property, Accumulated Depreciation, Depletion and Amortization

No definition available.

Name:	fdbc_FinanceLeaseLeasedPropertyAccumulatedDepreciationDepletionAndAmortization
Namespace Prefix:	fdbc_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant