Acquisition (Summary of Consideration Paid for MNB) (Details) - USD ($)		12 Months Ended
	May 01, 2020	Dec. 31, 2020	Dec. 31, 2019
Business Acquisition [Line Items]
Cash portion of purchase price (cash in lieu of fractional shares)		$ 4,000
Goodwill Recorded in Acquisition		$ 7,053,000	$ 209,000
MNB Corporation [Member]
Business Acquisition [Line Items]
MNB shares oustanding	1,132,873
Exchange ratio	1.039
Total FDBC shares	1,177,055
Shares paid in cash for fractional shares	84.71
Cash consideration (per MNB share)	$ 43.77
Cash portion of purchase price (cash in lieu of fractional shares)	$ 3,708
Total FDBC shares issued	1,176,970
FDBC's share price for purposes of calculation	$ 38.58
Equity portion of purchase price	$ 45,407,503
Total consideration paid	45,411,210
Total Purchase Price	45,411,000
Cash and cash equivalents	53,004,000
Investment securities	123,420,000
Loans held for sale	604,000
Loans	244,679,000
Restricted investments in bank stock	692,000
Premises and equipment	6,907,000
Core deposit intangible asset	1,973,000
Other assets	13,264,000
Total assets acquired	444,543,000
Non-interest bearing deposits	118,822,000
Interest bearing deposits	276,816,000
FHLB borrowings	7,627,000
Other liabilities	2,710,000
Total liabilities assumed	405,975,000
Net Assets Acquired	38,568,000
Goodwill Recorded in Acquisition	$ 6,843,000