LOANS AND CREDIT QUALITY - Activity in Allowance for Credit Losses by Loan Portfolio (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2024	Dec. 31, 2023
Allowance for credit losses by loan portfolio
Beginning balance	$ 40,500	$ 41,500
Charge-offs	(3,141)	(1,381)
Recoveries	707	448
Provision	677	(67)
Ending balance	38,743	40,500
Commercial and industrial loans \| Real Estate Sector
Allowance for credit losses by loan portfolio
Beginning balance	27,912	27,859
Charge-offs	0	0
Recoveries	0	0
Provision	(3,428)	53
Ending balance	24,484	27,912
Commercial and industrial loans \| Commercial and Industrial Sector
Allowance for credit losses by loan portfolio
Beginning balance	3,849	4,277
Charge-offs	(2,963)	(1,062)
Recoveries	522	87
Provision	6,054	547
Ending balance	7,462	3,849
Commercial and industrial loans \| Non-owner occupied CRE
Allowance for credit losses by loan portfolio
Beginning balance	2,610	2,102
Charge-offs	0	0
Recoveries	0	0
Provision	(871)	508
Ending balance	1,739	2,610
Commercial and industrial loans \| Multifamily
Allowance for credit losses by loan portfolio
Beginning balance	13,093	10,974
Charge-offs	0	0
Recoveries	0	0
Provision	1,816	2,119
Ending balance	14,909	13,093
Commercial and industrial loans \| Multifamily construction
Allowance for credit losses by loan portfolio
Beginning balance	3,983	998
Charge-offs	0	0
Recoveries	0	0
Provision	(3,134)	2,985
Ending balance	849	3,983
Commercial and industrial loans \| CRE construction
Allowance for credit losses by loan portfolio
Beginning balance	189	196
Charge-offs	0	0
Recoveries	0	0
Provision	(123)	(7)
Ending balance	66	189
Commercial and industrial loans \| Single family construction
Allowance for credit losses by loan portfolio
Beginning balance	7,365	12,418
Charge-offs	0	0
Recoveries	0	0
Provision	(628)	(5,053)
Ending balance	6,737	7,365
Commercial and industrial loans \| Single family construction to permanent
Allowance for credit losses by loan portfolio
Beginning balance	672	1,171
Charge-offs	0	0
Recoveries	0	0
Provision	(488)	(499)
Ending balance	184	672
Commercial and industrial loans \| Owner occupied CRE
Allowance for credit losses by loan portfolio
Beginning balance	899	1,030
Charge-offs	0	0
Recoveries	0	0
Provision	(323)	(131)
Ending balance	576	899
Commercial and industrial loans \| Commercial business
Allowance for credit losses by loan portfolio
Beginning balance	2,950	3,247
Charge-offs	(2,963)	(1,062)
Recoveries	522	87
Provision	6,377	678
Ending balance	6,886	2,950
Consumer Portfolio Segment
Allowance for credit losses by loan portfolio
Beginning balance	8,739	9,364
Charge-offs	(178)	(319)
Recoveries	185	361
Provision	(1,949)	(667)
Ending balance	6,797	8,739
Consumer Portfolio Segment \| Single family
Allowance for credit losses by loan portfolio
Beginning balance	5,287	5,610
Charge-offs	0	0
Recoveries	7	23
Provision	(1,684)	(346)
Ending balance	3,610	5,287
Consumer Portfolio Segment \| Home equity and other
Allowance for credit losses by loan portfolio
Beginning balance	3,452	3,754
Charge-offs	(178)	(319)
Recoveries	178	338
Provision	(265)	(321)
Ending balance	$ 3,187	$ 3,452

Amount excluding accrued interest, of allowance for credit loss on financing receivable. Excludes net investment in lease.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 45
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479344/326-20-45-1

+ Details

Name:	us-gaap_FinancingReceivableAllowanceForCreditLossExcludingAccruedInterest
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

+ References

No definition available.

+ Details

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

- Definition

Amount, excluding accrued interest, of increase in allowance for credit loss on financing receivable from recovery. Excludes net investment in lease.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Subparagraph (e)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479319/326-20-50-13

+ Details

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

- Definition

Amount, excluding accrued interest, of decrease in allowance for credit loss on financing receivable from writeoff. Excludes net investment in lease.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479319/326-20-50-6

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479319/326-20-50-13

+ Details

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

- Definition

Amount, excluding accrued interest, of credit loss expense (reversal of expense) on financing receivable. Excludes net investment in lease.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479319/326-20-50-13

+ Details

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

- Details

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

- Details

Name:	us-gaap_EquitySecuritiesByIndustryAxis=us-gaap_RealEstateSectorMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_EquitySecuritiesByIndustryAxis=us-gaap_CommercialAndIndustrialSectorMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

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

- Details

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

- Details

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

- Details

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

- Details

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

- Details

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

- Details

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

- Details

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