Investment Securities (Details Textual) $ in Millions	Mar. 31, 2018 USD ($)
Security Owned and Pledged as Collateral Carrying Value	$ 151.6
Investment Portfolio, Number of Securities	425
Investment Portfolio, Number of Securities, Unrealized Loss	167

Investment securities with a carrying amount and pledged to counterparties as collateral on public deposits for the period.

No definition available.

Name:	fdef_SecurityOwnedAndPledgedAsCollateralCarryingValue
Namespace Prefix:	fdef_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant