Allowance For Unfunded Commitments

No definition available.

Name:	hmst_AllowanceForUnfundedCommitments
Namespace Prefix:	hmst_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Loans Granted Forbearance, Outstanding Balance

+ References

No definition available.

+ Details

Name:	hmst_LoansGrantedForbearanceOutstandingBalance
Namespace Prefix:	hmst_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Loans In Process Of Forbearance Approval, Outstanding Balance

+ References

No definition available.

+ Details

Name:	hmst_LoansInProcessOfForbearanceApprovalOutstandingBalance
Namespace Prefix:	hmst_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Number Of Loans Granted Forbearance

+ References

No definition available.

+ Details

Name:	hmst_NumberOfLoansGrantedForbearance
Namespace Prefix:	hmst_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Number Of Loans In Process For Forbearance Approval

+ References

No definition available.

+ Details

Name:	hmst_NumberOfLoansInProcessForForbearanceApproval
Namespace Prefix:	hmst_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Percentage of total loan portfolio.

+ References

No definition available.

+ Details

Name:	hmst_PercentageOfLoanPortfolio
Namespace Prefix:	hmst_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Trouble Debt Restructuring, Re-Default, Number Of Days Past Due, Commercial

+ References

No definition available.

+ Details

Name:	hmst_TroubleDebtRestructuringReDefaultNumberOfDaysPastDueCommercial
Namespace Prefix:	hmst_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Trouble Debt Restructuring, Re-Default, Number of Days Past Due, Consumer

+ References

No definition available.

+ Details

Name:	hmst_TroubleDebtRestructuringReDefaultNumberOfDaysPastDueConsumer
Namespace Prefix:	hmst_
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_FinancingReceivableImpairedLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Carrying amount as of the balance sheet date of loans that have been pledged as collateral for borrowings. If the secured party has the right by contract or custom to sell or re-pledge the collateral, then the debtor reclassifies that asset and report that asset in its statement of financial position separately from other assets not so encumbered.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 30
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=66007379&loc=d3e113888-111728

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=118936363&loc=d3e5086-111524

+ Details

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

- Definition

Fair value portion of loan receivable, including, but not limited to, mortgage loans held for investment, finance receivables held for investment, policy loans on insurance contracts.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-URI http://asc.fasb.org/subtopic&trid=2196772

+ Details

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

- Definition

Amount, before allowance for credit loss, of financing receivable.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 50
-Paragraph 5
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=119407570&loc=SL82919230-210447

+ Details

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

- Definition

Number of operating segments. An operating segment is a component of an enterprise: (a) that engages in business activities from which it may earn revenues and incur expenses (including revenues and expenses relating to transactions with other components of the same enterprise), (b) whose operating results are regularly reviewed by the enterprise's chief operating decision maker to make decisions about resources to be allocated to the segment and assess its performance, and (c) for which discrete financial information is available. An operating segment may engage in business activities for which it has yet to earn revenues, for example, start-up operations may be operating segments before earning revenues.

+ References

No definition available.

+ Details

Name:	us-gaap_NumberOfOperatingSegments
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	srt_StatementGeographicalAxis=stpr_WA
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

Name:	srt_StatementGeographicalAxis=stpr_CA
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_FederalHomeLoanBankAdvancesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_FederalReserveBankAdvancesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

LOANS AND CREDIT QUALITY - Narrative (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2020 USD ($) segment	May 05, 2020 USD ($) loan	Dec. 31, 2019 USD ($)	Mar. 31, 2019 USD ($)
Financing Receivable, Impaired [Line Items]
Number of portfolio segments \| segment	2
Fair value of loans held for investment	$ 4,926		$ 3,468
Loans before allowance, net of deferred loan fees and costs	5,093,229		5,114,556
Allowance for unfunded commitments	$ 2,300		$ 1,100	$ 1,400
Number of days past due for consumer loans TDR to be re-default	60 days
Number of days past due for commercial loans TDR to be re-default	90 days
Washington \| Residential Mortgage And Multifamily [Member]
Financing Receivable, Impaired [Line Items]
Percentage of loan portfolio			10.70%
California \| Residential Mortgage And Multifamily [Member]
Financing Receivable, Impaired [Line Items]
Percentage of loan portfolio	14.90%		12.20%
Federal Home Loan Bank Advances [Member]
Financing Receivable, Impaired [Line Items]
Loans pledged as collateral	$ 1,880,000		$ 2,010,000
Federal Reserve Bank Advances [Member]
Financing Receivable, Impaired [Line Items]
Loans pledged as collateral	$ 430,000		$ 490,700
Subsequent Event [Member]
Financing Receivable, Impaired [Line Items]
Number of loans granted forbearance \| loan		393
Loans granted forbearance, outstanding balance		$ 223,000
Number of loans in process for forbearance approval \| loan		173
Loans in process of forbearance approval, outstanding balance		$ 204,000