Note 13 - Fair Value Measurements (Details Textual) $ in Thousands	12 Months Ended
Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers, Net, Total	$ 0	$ 0
Other Repossessed Assets	0	0
Loss from Hedged Firm Commitment Not Qualifying as Fair Value Hedge	$ 0	$ 0	$ 0
Measurement Input, Cost to Sell [Member] \| Minimum [Member]
Impaired Loans, Measurement Input	(0.1961)	(0.3308)
Measurement Input, Cost to Sell [Member] \| Maximum [Member]
Impaired Loans, Measurement Input	(0.2958)	(0.4766)
Measurement Input, Cost to Sell [Member] \| Weighted Average [Member]
Impaired Loans, Measurement Input	(0.2177)	(0.4450)
Measurement Input, Discount Rate [Member] \| Minimum [Member]
Other Real Estate Owned, Measurement Input	(0.3907)	(0.2016)
Measurement Input, Discount Rate [Member] \| Maximum [Member]
Other Real Estate Owned, Measurement Input	(0.7760)	(0.7760)
Measurement Input, Discount Rate [Member] \| Weighted Average [Member]
Other Real Estate Owned, Measurement Input	(0.3961)	(0.2821)

The measurement input for impaired loans.

No definition available.

Name:	fdbc_ImpairedLoansMeasurementInput
Namespace Prefix:	fdbc_
Data Type:	xbrli:decimalItemType
Balance Type:	na
Period Type:	instant

- Definition

Amount of transfer of financial instrument classified as an asset into (out of) level 3 of the fair value hierarchy.

+ References

No definition available.

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of loss recognized in earnings when a hedged firm commitment no longer qualifies as a fair value hedge.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4C
-Subparagraph (g)
-URI https://asc.fasb.org/extlink&oid=125515794&loc=SL5624171-113959

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 25
-Section 50
-Paragraph 1
-Subparagraph (b)
-URI https://asc.fasb.org/extlink&oid=121577467&loc=d3e76258-113986

+ Details

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Period Type:	duration

- Definition

Carrying amount as of the balance sheet date of assets other than real property that were received in full or partial satisfaction of a debt arrangement through foreclosure proceedings or defeasance.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 11
-URI https://asc.fasb.org/extlink&oid=123577603&loc=d3e5162-111524

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 45
-Paragraph 3
-URI https://asc.fasb.org/extlink&oid=124259787&loc=d3e4437-111522

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Balance Type:	debit
Period Type:	instant

- Definition

Value of input used to measure real estate owned by financial institution by financial institution which is not directly related to its business.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (bbb)(2)
-URI https://asc.fasb.org/extlink&oid=126976982&loc=d3e19207-110258

+ Details

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- Details

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- Details

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