Cash and Due from Banks (Narrative) (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018
Cash and Due from Banks
Amount of required reserve balance with Federal Reserve Bank	$ 0	$ 0

Amount of reserve balance required to maintain with the Federal Reserve Bank (FRB).

No definition available.

Name:	ffbw_AmountOfRequiredReserveBalanceWithFederalReserveBank
Namespace Prefix:	ffbw_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration