Investment Securities Available for Sale (Weighted Average Yield)(Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Mortgage Backed and Collateral Mortgage Obligation
Available-for-sale Securities, Debt Maturities, Next Twelve Months, Fair Value	$ 26,010	$ 25,998
Available-for-sale Securities, Debt Maturities, Year Two Through Five, Fair Value	27,646	24,595
Available-for-sale Securities, Debt Maturities, Year Six Through Ten, Fair Value	76,496	78,677
Available-for-sale Securities, Debt Maturities, after Ten Years, Fair Value	319,178	298,056
Available-for-sale Securities, Debt Securities	449,330	427,326
Available for Sale Securities Debt Maturities with in One Year Weighted Average Yield	0.28%	0.28%
Available-for-sale Securities, Debt Maturities, Year Two Through Five, Weighted Average Yield	1.46%	1.19%
Available for Sale Securities Debt Maturities After Five Through Ten Years Weighted Average Yield	3.10%	3.09%
Available for Sale Securities Debt Maturities After Ten Years Weighted Average Yield	2.78%	2.92%
Available for Sale Securities Debt Maturities Without Single Maturity Date Weighted Average Yield	2.61%	2.69%
Residential Mortgage Backed Securities [Member]
Mortgage Backed and Collateral Mortgage Obligation
Available-for-sale Securities, Debt Maturities, Next Twelve Months, Fair Value	0	0
Available-for-sale Securities, Debt Maturities, Year Two Through Five, Fair Value	6	0
Available-for-sale Securities, Debt Maturities, Year Six Through Ten, Fair Value	6,535	6,949
Available-for-sale Securities, Debt Maturities, after Ten Years, Fair Value	107,634	100,331
Available-for-sale Securities, Debt Securities	114,175	107,280
Available for Sale Securities Debt Maturities with in One Year Weighted Average Yield	0.00%	0.00%
Available-for-sale Securities, Debt Maturities, Year Two Through Five, Weighted Average Yield	0.46%	0.00%
Available for Sale Securities Debt Maturities After Five Through Ten Years Weighted Average Yield	1.76%	1.72%
Available for Sale Securities Debt Maturities After Ten Years Weighted Average Yield	1.77%	1.75%
Available for Sale Securities Debt Maturities Without Single Maturity Date Weighted Average Yield	1.77%	1.75%
Commercial Mortgage Backed Securities [Member]
Mortgage Backed and Collateral Mortgage Obligation
Available-for-sale Securities, Debt Maturities, Next Twelve Months, Fair Value	0	0
Available-for-sale Securities, Debt Maturities, Year Two Through Five, Fair Value	0	0
Available-for-sale Securities, Debt Maturities, Year Six Through Ten, Fair Value	0	0
Available-for-sale Securities, Debt Maturities, after Ten Years, Fair Value	13,667	13,671
Available-for-sale Securities, Debt Securities	13,667	13,671
Available for Sale Securities Debt Maturities with in One Year Weighted Average Yield	0.00%	0.00%
Available-for-sale Securities, Debt Maturities, Year Two Through Five, Weighted Average Yield	0.00%	0.00%
Available for Sale Securities Debt Maturities After Five Through Ten Years Weighted Average Yield	0.00%	0.00%
Available for Sale Securities Debt Maturities After Ten Years Weighted Average Yield	4.82%	4.75%
Available for Sale Securities Debt Maturities Without Single Maturity Date Weighted Average Yield	4.82%	4.75%
Municipal Bonds [Member]
Mortgage Backed and Collateral Mortgage Obligation
Available-for-sale Securities, Debt Maturities, Next Twelve Months, Fair Value	0	0
Available-for-sale Securities, Debt Maturities, Year Two Through Five, Fair Value	2,506	604
Available-for-sale Securities, Debt Maturities, Year Six Through Ten, Fair Value	22,337	23,465
Available-for-sale Securities, Debt Maturities, after Ten Years, Fair Value	97,591	98,265
Available-for-sale Securities, Debt Securities	122,434	122,334
Available for Sale Securities Debt Maturities with in One Year Weighted Average Yield	0.00%	0.00%
Available-for-sale Securities, Debt Maturities, Year Two Through Five, Weighted Average Yield	3.89%	4.10%
Available for Sale Securities Debt Maturities After Five Through Ten Years Weighted Average Yield	3.52%	3.55%
Available for Sale Securities Debt Maturities After Ten Years Weighted Average Yield	4.24%	4.21%
Available for Sale Securities Debt Maturities Without Single Maturity Date Weighted Average Yield	4.10%	4.09%
Residential [Member]
Mortgage Backed and Collateral Mortgage Obligation
Available-for-sale Securities, Debt Maturities, Next Twelve Months, Fair Value	0	0
Available-for-sale Securities, Debt Maturities, Year Two Through Five, Fair Value	0	0
Available-for-sale Securities, Debt Maturities, Year Six Through Ten, Fair Value	181	0
Available-for-sale Securities, Debt Maturities, after Ten Years, Fair Value	58,295	43,166
Available-for-sale Securities, Debt Securities	58,476	43,166
Available for Sale Securities Debt Maturities with in One Year Weighted Average Yield	0.00%	0.00%
Available-for-sale Securities, Debt Maturities, Year Two Through Five, Weighted Average Yield	0.00%	0.00%
Available for Sale Securities Debt Maturities After Five Through Ten Years Weighted Average Yield	0.83%	0.00%
Available for Sale Securities Debt Maturities After Ten Years Weighted Average Yield	1.43%	1.84%
Available for Sale Securities Debt Maturities Without Single Maturity Date Weighted Average Yield	1.43%	1.84%
Commercial [Member]
Mortgage Backed and Collateral Mortgage Obligation
Available-for-sale Securities, Debt Maturities, Next Twelve Months, Fair Value	0	0
Available-for-sale Securities, Debt Maturities, Year Two Through Five, Fair Value	0	0
Available-for-sale Securities, Debt Maturities, Year Six Through Ten, Fair Value	9,892	9,776
Available-for-sale Securities, Debt Maturities, after Ten Years, Fair Value	9,902	10,710
Available-for-sale Securities, Debt Securities	19,794	20,486
Available for Sale Securities Debt Maturities with in One Year Weighted Average Yield	0.00%	0.00%
Available-for-sale Securities, Debt Maturities, Year Two Through Five, Weighted Average Yield	0.00%	0.00%
Available for Sale Securities Debt Maturities After Five Through Ten Years Weighted Average Yield	1.97%	1.96%
Available for Sale Securities Debt Maturities After Ten Years Weighted Average Yield	1.68%	1.99%
Available for Sale Securities Debt Maturities Without Single Maturity Date Weighted Average Yield	1.83%	1.97%
Corporate Debt Securities [Member]
Mortgage Backed and Collateral Mortgage Obligation
Available-for-sale Securities, Debt Maturities, Next Twelve Months, Fair Value	0	0
Available-for-sale Securities, Debt Maturities, Year Two Through Five, Fair Value	10,129	9,000
Available-for-sale Securities, Debt Maturities, Year Six Through Ten, Fair Value	37,551	38,487
Available-for-sale Securities, Debt Maturities, after Ten Years, Fair Value	32,089	31,913
Available-for-sale Securities, Debt Securities	79,769	79,400
Available for Sale Securities Debt Maturities with in One Year Weighted Average Yield	0.00%	0.00%
Available-for-sale Securities, Debt Maturities, Year Two Through Five, Weighted Average Yield	2.37%	2.21%
Available for Sale Securities Debt Maturities After Five Through Ten Years Weighted Average Yield	3.39%	3.35%
Available for Sale Securities Debt Maturities After Ten Years Weighted Average Yield	3.84%	3.73%
Available for Sale Securities Debt Maturities Without Single Maturity Date Weighted Average Yield	3.44%	3.37%
US Treasury Securities [Member]
Mortgage Backed and Collateral Mortgage Obligation
Available-for-sale Securities, Debt Maturities, Next Twelve Months, Fair Value	26,010	25,998
Available-for-sale Securities, Debt Maturities, Year Two Through Five, Fair Value	15,005	14,991
Available-for-sale Securities, Debt Maturities, Year Six Through Ten, Fair Value	0	0
Available-for-sale Securities, Debt Maturities, after Ten Years, Fair Value	0	0
Available-for-sale Securities, Debt Securities	$ 41,015	$ 40,989
Available for Sale Securities Debt Maturities with in One Year Weighted Average Yield	0.28%	0.28%
Available-for-sale Securities, Debt Maturities, Year Two Through Five, Weighted Average Yield	0.46%	0.46%
Available for Sale Securities Debt Maturities After Five Through Ten Years Weighted Average Yield	0.00%	0.00%
Available for Sale Securities Debt Maturities After Ten Years Weighted Average Yield	0.00%	0.00%
Available for Sale Securities Debt Maturities Without Single Maturity Date Weighted Average Yield	0.35%	0.35%

Available for sale securities debt maturities after five through ten years weighted average yield.

No definition available.

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

- Definition

Available-for-sale securities debt maturities year two through five fair value

+ References

No definition available.

+ Details

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

- Definition

Available for sale securities debt maturities after ten years weighted average yield.

+ References

No definition available.

+ Details

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

- Definition

Available for sale securities debt maturities with in one year weighted average yield.

+ References

No definition available.

+ Details

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

- Definition

Available for sale securities debt maturities without single maturity date weighted average yield.

+ References

No definition available.

+ Details

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

- Details

Name:	hmst_MortgageBackedAndCollateralMortgageObligationAbstract
Namespace Prefix:	hmst_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Fair value of available-for-sale debt securities maturing in the sixth fiscal year through the tenth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 50

-Paragraph 3

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27198-111563

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (d)

-URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27161-111563

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 320

-Section 50

-Paragraph 3

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=6957658&loc=d3e62586-112803

+ Details

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

- Definition

Fair value of available-for-sale debt securities maturing in the second fiscal year through the fifth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (d)

-URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27161-111563

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 50

-Paragraph 3

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27198-111563

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 320

-Section 50

-Paragraph 3

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=6957658&loc=d3e62586-112803

+ Details

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

- Definition

Fair value of available-for-sale debt securities maturing after the tenth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (d)

-URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27161-111563

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 50

-Paragraph 3

-Subparagraph (d)

-URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27198-111563

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 320

-Section 50

-Paragraph 3

-Subparagraph (d)

-URI http://asc.fasb.org/extlink&oid=6957658&loc=d3e62586-112803

+ Details

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

- Definition

Fair value of available-for-sale debt securities maturing in the next fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 50

-Paragraph 3

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27198-111563

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 320

-Section 50

-Paragraph 3

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=6957658&loc=d3e62586-112803

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (d)

-URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27161-111563

+ Details

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

- Definition

Amount of debt securities categorized neither as held-to-maturity nor trading.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 25

-Paragraph 1

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=28360136&loc=d3e22054-111558

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (aa)

-URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27161-111563

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 45

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6871852&loc=d3e26610-111562

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 320

-Section 50

-Paragraph 2

-Subparagraph (b)-(g)

-URI http://asc.fasb.org/extlink&oid=6957658&loc=d3e62557-112803

+ Details

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

- Details

Name:	us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis=hmst_CollateralizedCommercialMortgageObligationsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis=hmst_CollateralizedResidentialMortgageObligationsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis=us-gaap_CommercialMortgageBackedSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis=us-gaap_CorporateDebtSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis=us-gaap_MunicipalBondsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis=us-gaap_ResidentialMortgageBackedSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis=us-gaap_USTreasurySecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: