Represents percentage of common stock outstanding to bank eligible members.

No definition available.

Name:	ffbw_PercentageOfCommonStockOutstandingToBankEligibleMembers
Namespace Prefix:	ffbw_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage of common stock to be outstanding upon completion of the reorganization and stock issuance.

+ References

No definition available.

+ Details

Name:	ffbw_PercentageOfCommonStockOutstandingUponCompletionOfReorganizationAndStockIssuance
Namespace Prefix:	ffbw_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage of common stock subscribe to adopt employee stock ownership plan.

+ References

No definition available.

+ Details

Name:	ffbw_PercentageOfCommonStockSubscribeToAdoptEmployeeStockOwnershipPlan
Namespace Prefix:	ffbw_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

The percentage of outstanding shares authorized to be repurchased under the stock repurchase program.

+ References

No definition available.

+ Details

Name:	ffbw_StockRepurchaseProgramPercentageOfSharesAuthorizedToBeRepurchased
Namespace Prefix:	ffbw_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 22
-Subparagraph (h)
-URI http://asc.fasb.org/extlink&oid=115929826&loc=d3e8736-108599

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(h))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 20
-Section 45
-Paragraph 2
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=109238882&loc=d3e38679-109324

+ Details

Name:	us-gaap_IncomeTaxExpenseBenefit
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The cash outflow for cost incurred directly with the issuance of an equity security.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 15
-URI http://asc.fasb.org/extlink&oid=109223946&loc=d3e3291-108585

+ Details

Name:	us-gaap_PaymentsOfStockIssuanceCosts
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Per share amount received by subsidiary or equity investee for each share of common stock issued or sold in the stock transaction.

+ References

No definition available.

+ Details

Name:	us-gaap_SaleOfStockPricePerShare
Namespace Prefix:	us-gaap_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	instant

- Definition

Number of new stock issued during the period.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(29))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21463-112644

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.3-04)
-URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187085-122770

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(28))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

Name:	us-gaap_StockIssuedDuringPeriodSharesNewIssues
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of expense for interest on an underpayment of income taxes and penalties related to a tax position claimed or expected to be claimed in the tax return.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 15
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32718-109319

+ Details

Name:	us-gaap_UnrecognizedTaxBenefitsIncomeTaxPenaltiesAndInterestExpense
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Details

Name:	us-gaap_SubsequentEventTypeAxis=us-gaap_SubsequentEventMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis=us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_IncomeStatementLocationAxis=ffbw_NetGainOnSaleOfSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	dei_LegalEntityAxis=ffbw_FFBWCommunityFoundationMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	dei_LegalEntityAxis=ffbw_FFBWMHCMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Note 1 - Summary of Significant Accounting Policies (Details Textual) - USD ($) $ / shares in Units, $ in Thousands			12 Months Ended
	Jan. 25, 2019	Oct. 10, 2017	Dec. 31, 2018	Dec. 31, 2017
Stock Issued During Period, Shares, New Issues		2,950,625
Sale of Stock, Price Per Share		$ 10
Payments of Stock Issuance Costs		$ 1,394
Unrecognized Tax Benefits, Income Tax Penalties and Interest Expense, Total			$ 0	$ 0
Income Tax Expense (Benefit), Total			318	264
Subsequent Event [Member]
Stock Repurchase Program, Percentage of Shares Authorized to be Repurchased	5.00%
Reclassification out of Accumulated Other Comprehensive Income [Member] \| Net Gain on Sale of Securities [Member]
Income Tax Expense (Benefit), Total			$ 56	$ 5
FFBW Community Foundation [Member]
Stock Issued During Period, Shares, New Issues		25,000
Percentage of Common Stock Outstanding to Bank Eligible Members		45.00%
Percentage of Common Stock Subscribe to Adopt Employee Stock Ownership Plan		3.92%
FFBW, MHC [Member]
Stock Issued During Period, Shares, New Issues		3,636,875
Percentage of Common Stock Outstanding Upon Completion of Reorganization and Stock Issuance		55.00%