Loans, Credit Risk Profile Based on Payment Activity (Details) - USD ($) $ in Thousands	9 Months Ended
Sep. 30, 2016	Dec. 31, 2015
Credit Risk Profile by Type of Loan [Abstract]
Total loans	$ 478,983	$ 461,176
Minimum [Member]
Financing Receivable, Recorded Investment [Line Items]
Period past due for loans still accruing interest to be considered nonperforming	90 days
Period of performance according to modified terms for TDR to be removed from nonperforming status	9 months
Period past due for TDRs loans to be considered nonperforming	30 days
Performing [Member]
Credit Risk Profile by Type of Loan [Abstract]
Total loans	$ 474,114	459,046
Nonperforming [Member]
Credit Risk Profile by Type of Loan [Abstract]
Total loans	4,869	2,130
One-to Four- Family [Member]
Credit Risk Profile by Type of Loan [Abstract]
Total loans	151,992	141,125
One-to Four- Family [Member] \| Performing [Member]
Credit Risk Profile by Type of Loan [Abstract]
Total loans	150,437	139,484
One-to Four- Family [Member] \| Nonperforming [Member]
Credit Risk Profile by Type of Loan [Abstract]
Total loans	1,555	1,641
Home Equity [Member]
Credit Risk Profile by Type of Loan [Abstract]
Total loans	30,297	31,573
Home Equity [Member] \| Performing [Member]
Credit Risk Profile by Type of Loan [Abstract]
Total loans	29,717	31,146
Home Equity [Member] \| Nonperforming [Member]
Credit Risk Profile by Type of Loan [Abstract]
Total loans	580	427
Commercial and Multifamily [Member]
Credit Risk Profile by Type of Loan [Abstract]
Total loans	170,258	175,312
Commercial and Multifamily [Member] \| Performing [Member]
Credit Risk Profile by Type of Loan [Abstract]
Total loans	167,921	175,312
Commercial and Multifamily [Member] \| Nonperforming [Member]
Credit Risk Profile by Type of Loan [Abstract]
Total loans	2,337	0
Construction and Land [Member]
Credit Risk Profile by Type of Loan [Abstract]
Total loans	58,902	57,043
Construction and Land [Member] \| Performing [Member]
Credit Risk Profile by Type of Loan [Abstract]
Total loans	58,902	57,043
Construction and Land [Member] \| Nonperforming [Member]
Credit Risk Profile by Type of Loan [Abstract]
Total loans	0	0
Manufactured Homes [Member]
Credit Risk Profile by Type of Loan [Abstract]
Total loans	15,525	13,798
Manufactured Homes [Member] \| Performing [Member]
Credit Risk Profile by Type of Loan [Abstract]
Total loans	15,377	13,736
Manufactured Homes [Member] \| Nonperforming [Member]
Credit Risk Profile by Type of Loan [Abstract]
Total loans	148	62
Other Consumer [Member]
Credit Risk Profile by Type of Loan [Abstract]
Total loans	25,570	23,030
Other Consumer [Member] \| Performing [Member]
Credit Risk Profile by Type of Loan [Abstract]
Total loans	25,570	23,030
Other Consumer [Member] \| Nonperforming [Member]
Credit Risk Profile by Type of Loan [Abstract]
Total loans	0	0
Commercial Business [Member]
Credit Risk Profile by Type of Loan [Abstract]
Total loans	26,439	19,295
Commercial Business [Member] \| Performing [Member]
Credit Risk Profile by Type of Loan [Abstract]
Total loans	26,190	19,295
Commercial Business [Member] \| Nonperforming [Member]
Credit Risk Profile by Type of Loan [Abstract]
Total loans	$ 249	$ 0

No definition available.

Name:	sfbc_CreditRiskProfileByTypeOfLoanAbstract
Namespace Prefix:	sfbc_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Refers to the period of performance according to modified terms for TDR to be removed from nonperforming status, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

+ Details

Name:	sfbc_PeriodOfPerformanceAccordingToModifiedTermsForTDRToBeRemovedFromNonperformingStatus
Namespace Prefix:	sfbc_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Refers to the period past due for loans still accruing interest to be considered nonperforming, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

+ Details

Name:	sfbc_PeriodPastDueForLoansStillAccruingInterestToBeConsideredNonperforming
Namespace Prefix:	sfbc_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Refers to the Period past due for TDRs loans to be considered nonperforming, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

+ Details

Name:	sfbc_PeriodPastDueForTDRsLoansToBeConsideredNonperforming
Namespace Prefix:	sfbc_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount before allowance of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Includes deferred interest and fees, undisbursed portion of loan balance, unamortized costs and premiums and discounts from face amounts. Excludes loans and leases covered under loss sharing agreements.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=65884687&loc=d3e4428-111522

+ Details

Name:	us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Details

Name:	us-gaap_RangeAxis=us-gaap_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentPerformanceStatusAxis=us-gaap_PerformingFinancingReceivableMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentPerformanceStatusAxis=us-gaap_NonperformingFinancingReceivableMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=us-gaap_ResidentialMortgageMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=us-gaap_HomeEquityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=sfbc_CommercialAndMultifamilyRealEstateLoanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=sfbc_ConstructionAndLandMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=sfbc_ManufacturedHomesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=sfbc_OtherConsumerFinancingReceivableMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=us-gaap_CommercialPortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: