Income Tax Disclosure [Abstract] Federal statutory tax rate (as a percent) Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent Income tax expense at Federal statutory rate Effective Income Tax Rate Reconciliation at Federal Statutory Income Tax Rate, Amount Tax-exempt instruments Effective Income Tax Rate Reconciliation, Tax Exempt Income, Amount Non-deductible acquisition costs Effective Income Tax Rate Reconciliation, Nondeductible Expense, Acquisition Costs, Amount Effective Income Tax Rate Reconciliation, Nondeductible Expense, Acquisition Costs, Amount Federal tax credits and other benefits Effective Income Tax Rate Reconciliation, Tax Credit, Amount Effects of BOLI IncomeTaxReconciliationBankOwnedLifeInsuranceTaxFeeIncome Amount of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to tax free bank owned life insurance income recorded Revaluation of net deferred tax assets Effective Income Tax Rate Reconciliation, Change in Enacted Tax Rate, Amount Other, net Effective Income Tax Rate Reconciliation, Other Adjustments, Amount Income tax expense Income Tax Expense (Benefit) Amortizaon of LIHTC Amortization Method Qualified Affordable Housing Project Investments, Amortization Goodwill and Intangible Assets Disclosure [Abstract] Change in goodwill Schedule of Goodwill [Table Text Block] Change in other intangible assets Schedule of Finite-Lived Intangible Assets [Table Text Block] Estimated aggregate amortization expense for future years Schedule of Finite-Lived Intangible Assets, Future Amortization Expense [Table Text Block] Deposits [Abstract] Schedule of deposits Schedule of Interest Bearing Deposit Liabilities Domestic by Component [Table Text Block] Schedule of interest bearing deposit liabilities domestic by component. Schedule of interest expense, by category Schedule of Interest Expense Deposits [Table Text Block] Schedule of interest expense deposits. Schedule of maturities of certificates of deposit Schedule of Maturities of Time Deposits [Table Text Block] Schedule of maturities of time deposits. Statement of Stockholders' Equity [Abstract] Statement [Table] Statement [Table] Equity Components [Axis] Equity Components [Axis] Equity Component [Domain] Equity Component [Domain] Common stock Common Stock [Member] Retained earnings Retained Earnings [Member] Accumulated other comprehensive income (loss), net AOCI Attributable to Parent [Member] Statement [Line Items] Statement [Line Items] Increase (Decrease) in Stockholders' Equity [Roll Forward] Increase (Decrease) in Stockholders' Equity [Roll Forward] Balance at beginning of the year, shares Shares, Outstanding Balance at the beginning of the year Stockholders' Equity Attributable to Parent Restricted stock awards granted, net of forfeitures, shares Stock Issued During Period, Shares, Restricted Stock Award, Net of Forfeitures Restricted stock awards granted, net of forfeitures Stock Issued During Period, Value, Restricted Stock Award, Net of Forfeitures Restricted stock units vested, net of restricted stock awards forfeited, shares Stock Vested During Period, Shares, Restricted Stock Units Stock Vested During Period, Shares, Restricted Stock Units Restricted stock units vested, net of restricted stock awards forfeited Stock Vested During Period, Value, Restricted Stock Units Stock Vested During Period, Value, Restricted Stock Units Restricted stock awards forfeited, shares Stock Issued During Period, Shares, Restricted Stock Award, Forfeited Restricted stock awards forfeited Stock Issued During Period, Value, Restricted Stock Award, Forfeitures Exercise of stock options, shares Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period Exercise of stock options Stock Issued During Period, Value, Stock Options Exercised Stock-based compensation expense Adjustments to Additional Paid in Capital, Share-based Compensation, Restricted Stock Unit or Restricted Stock Award, Requisite Service Period Recognition Net excess tax benefits from vesting of restricted stock Adjustment to Additional Paid in Capital, Income Tax Effect from Share-based Compensation, Net Common stock repurchased, shares Stock Repurchased and Retired During Period, Shares Common stock repurchased Stock Repurchased and Retired During Period, Value Net income Net Income (Loss) Attributable to Parent Other comprehensive income (loss), net of tax Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent Common stock issued in business combinations, shares Stock Issued During Period, Shares, Acquisitions Common stock issued in business combinations Stock Issued During Period, Value, Acquisitions Cash dividends declared on common stock Dividends, Common Stock, Cash ASU Implementation Cumulative Effect of New Accounting Principle in Period of Adoption Balance at end of the year, shares Balance at the end of the year Fair Value Disclosures [Abstract] Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Table] Fair Value Measurements, Recurring and Nonrecurring [Table] Measurement Frequency [Axis] Measurement Frequency [Axis] Fair Value, Measurement Frequency [Domain] Fair Value, Measurement Frequency [Domain] Nonrecurring Fair Value, Measurements, Nonrecurring [Member] Financial Instrument Performance Status [Axis] Financial Instrument Performance Status [Axis] Financial Instrument Performance Status [Domain] Financial Instrument Performance Status [Domain] Impaired Loans Impaired Loans [Member] Impaired Loans [Member] Financing Receivable Portfolio Segment [Axis] Financing Receivable Portfolio Segment [Axis] Financing Receivable Portfolio Segment [Domain] Financing Receivable Portfolio Segment [Domain] Commercial business Commercial Portfolio Segment [Member] Consumer Consumer Portfolio Segment [Member] Class of Financing Receivable, Type [Axis] Class of Financing Receivable, Type [Axis] Class of Financing Receivable, Type [Domain] Class of Financing Receivable, Type [Domain] Commercial and industrial Commercial and Industrial [Member] Commercial and industrial. Non-owner occupied commercial real estate Non Owner Occupied Commercial Real Estate [Member] Non owner occupied commercial real estate. One-to-four family residential One to Four Family Real Estate Construction [Member] One to Four Family Real Estate Construction [Member] Fair Value, Hierarchy [Axis] Fair Value, Hierarchy [Axis] Fair Value, Measurements, Fair Value Hierarchy [Domain] Fair Value Hierarchy [Domain] Level 1 Fair Value, Inputs, Level 1 [Member] Level 2 Fair Value, Inputs, Level 2 [Member] Level 3 Fair Value, Inputs, Level 3 [Member] Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] Basis Basis for Assets Measured at Fair Value Basis for assets measured at fair value. Fair Value Loans Receivable, Fair Value Disclosure Net Losses (Gains) Recorded in Earnings Fair Value Assets Measured on Nonrecurring Basis Net Gains Losses Included in Earnings Amount of net gains and losses recorded in earnings for nonrecurring assets reported at fair value Receivables [Abstract] Schedule of Accounts, Notes, Loans and Financing Receivable [Table] Schedule of Accounts, Notes, Loans and Financing Receivable [Table] One-to-four family residential Residential Portfolio Segment [Member] Range [Axis] Range [Axis] Range [Domain] Range [Domain] Minimum Minimum [Member] Maximum Maximum [Member] Accounts, Notes, Loans and Financing Receivable [Line Items] Accounts, Notes, Loans and Financing Receivable [Line Items] Number of loan segments Number of Loan Segments Number of loan segments. Maximum percent of appraised value or underlying collateral mortgage (not to exceed 80%) residential loans (percent) Maximum Loans and Leases Receivable Percent of Appraised Value or Underlying Collateral Mortgage Residential Loans Maximum loans and leases receivable percent of appraised value or underlying collateral mortgage residential loans. Loan term Loans and Leases Receivable, maturity Term Loans and leases receivable, maturity term. Maximum percentage consumer loans (percent) Loans and Leases Receivable Maximum Percentage Consumer Loans Loans and leases receivable maximum percentage consumer loans. Accrued interest payable on deposits Deposit Liabilities, Accrued Interest Certificates of deposit equal to or in excess of $250,000 Time Deposits, $250,000 or More, Domestic Time Deposits, $250,000 or More, Domestic Equity [Abstract] AOCI attributable to parent Other comprehensive (loss) income before reclassification Other Comprehensive Income (Loss), before Reclassifications, Net of Tax Amounts reclassified from AOCI for gain on sale of investment securities included in net income Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax Other comprehensive (loss) income Real estate construction and land development Real Estate Construction and Land Development [Member] Total real estate construction and land development. Owner-occupied commercial real estate Owner Occupied Commercial Real Estate [Member] Owner occupied commercial real estate. Five or more family residential and commercial properties Five or More Family Residential and Commercial Properties [Member] Five or more family residential and commercial properties. Gross loans receivable Loans and Leases Receivable, Gross Net deferred loan costs Unamortized Loan Commitment and Origination Fees and Unamortized Discounts or Premiums Loans receivable, net Loans and Leases Receivable, Net of Deferred Income Allowance for loan losses Loans and Leases Receivable, Allowance Total loans receivable, net Loans and Leases Receivable, Net Amount Stockholders' Equity Note [Abstract] Subsequent Event [Table] Subsequent Event [Table] Dividends [Axis] Dividends [Axis] Dividends [Domain] Dividends [Domain] Special Dividend Special Dividend [Member] Special Dividend [Member] Subsequent Event [Line Items] Subsequent Event [Line Items] Declared Dividends Payable, Date Declared Cash Dividend per Share (in usd per share) Common Stock, Dividends, Per Share, Declared Record Date Dividends Payable, Date of Record Paid Date Dividends Payable, Date to be Paid Regulatory Capital Requirements [Abstract] Regulatory Capital Requirements Regulatory Capital Requirements under Banking Regulations [Text Block] Anti-dilutive securities excluded from computation Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount Dividends declared per common share (in usd per share) Condensed Financial Information of Parent Company Only Disclosure [Abstract] Condensed Balance Sheet Statement [Table] Condensed Balance Sheet Statement [Table] Consolidated Entities [Axis] Consolidated Entities [Axis] Consolidated Entities [Domain] Consolidated Entities [Domain] Parent Company Parent Company [Member] Condensed Balance Sheet Statements, Captions [Line Items] Condensed Balance Sheet Statements, Captions [Line Items] ASSETS Assets [Abstract] Cash and interest earning deposits Cash Equivalents, at Carrying Value Investment in subsidiary bank Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures Other assets Other Assets Total assets Assets LIABILITIES AND STOCKHOLDERS’ EQUITY Liabilities and Equity [Abstract] Junior subordinated debentures Junior Subordinated Notes Other liabilities Other Liabilities Total stockholders’ equity Total liabilities and stockholders’ equity Liabilities and Equity Condensed Cash Flow Statement [Table] Condensed Cash Flow Statement [Table] Condensed Cash Flow Statements, Captions [Line Items] Condensed Cash Flow Statements, Captions [Line Items] Cash flows from operating activities: Net Cash Provided by (Used in) Operating Activities [Abstract] Adjustments to reconcile net income to net cash provided by operating activities: Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract] Equity in undistributed income of subsidiary bank Equity in Undistributed Income of Subsidiaries Equity in Undistributed Income of Subsidiaries Net excess tax benefit from exercise of stock options and vesting of restricted stock Employee Service Share-based Compensation, Tax Benefit from Exercise of Stock Options Stock-based compensation expense Employee Benefits and Share-based Compensation Net change in other assets and liabilities Increase (Decrease) in Other Current Assets and Liabilities, Net Net cash provided by operating activities Net Cash Provided by (Used in) Operating Activities Cash flows from investing activities: Net Cash Provided by (Used in) Investing Activities [Abstract] Net cash received from acquisitions Cash Acquired from Acquisition Net cash used in investing activities Net Cash Provided by (Used in) Investing Activities Cash flows from financing activities: Net Cash Provided by (Used in) Financing Activities [Abstract] Common stock cash dividends paid Payments of Ordinary Dividends, Common Stock Proceeds from exercise of stock options Proceeds from Stock Options Exercised Net excess tax benefit from exercise of stock options and vesting of restricted stock Excess Tax Benefit from Share-based Compensation, Financing Activities Repurchase of common stock Payments for Repurchase of Common Stock Net cash provided by financing activities Net Cash Provided by (Used in) Financing Activities Net increase (decrease) in cash and cash equivalents Cash and Cash Equivalents, Period Increase (Decrease) Cash and cash equivalents at the beginning of year Cash and cash equivalents at the end of year Supplemental non-cash disclosures of cash flow information: Supplemental Cash Flow Information [Abstract] Common stock issued for business combinations Common Stock issued Business Combinations Common Stock issued Business Combinations Capital contribution of net assets acquired in business combinations to Bank Capital Contribution Net Assets Acquired in Business Combinations Capital Contribution Net Assets Acquired in Business Combinations Schedule of earnings per share reconciliation Schedule of Earnings Per Share Reconciliation [Abstract] Schedule of earnings per share reconciliation. Net income: Net Income (Loss) Available to Common Stockholders, Diluted [Abstract] Dividends and undistributed earnings allocated to participating securities Dividends and Undistributed Earnings Dividends and undistributed earnings. Net income allocated to common shareholders Undistributed Earnings, Diluted Basic: Weighted Average Number of Shares Outstanding, Basic [Abstract] Weighted average common shares outstanding (in shares) Gross Weighted Average Number of Shares Outstanding Basic Gross weighted average number of shares outstanding basic. Restricted stock awards (in shares) Weighted Average Number of Shares, Restricted Stock Total basic weighted average common shares outstanding (in shares) Weighted Average Number of Shares Outstanding, Basic Diluted: Weighted Average Number of Shares Outstanding, Diluted [Abstract] Basic weighted average common shares outstanding (in shares) Effect of potentially dilutive common shares (in shares) Weighted Average Number Diluted Shares Outstanding Adjustment Total diluted weighted average common shares outstanding (in shares) Weighted Average Number of Shares Outstanding, Diluted Derivative Instruments and Hedging Activities Disclosure [Abstract] Derivative Financial Instruments Derivative Instruments and Hedging Activities Disclosure [Text Block] Income Taxes Income Tax Disclosure [Text Block] Disclosure of Compensation Related Costs, Share-based Payments [Abstract] Stock option activity Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward] Shares Share-based Compensation Arrangement by Share-based Payment Award, Options, Nonvested, Number of Shares [Roll Forward] Outstanding at beginning of period (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number Exercised (in shares) Forfeited or expired (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Forfeitures and Expirations in Period Outstanding at end of period (in shares) Vested and expected to vest at end of period (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Number Exercisable at end of period (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Number Weighted-Average Exercise Price Share-based Compensation Arrangement by Share-based Payment Award, Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract] Outstanding at beginning of period (in usd per share) Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price Exercised (in usd per share) Share-based Compensation Arrangements by Share-based Payment Award, Options, Exercises in Period, Weighted Average Exercise Price Forfeited or expired (in usd per share) Share-based Compensation Arrangement by Share-based Payment Award, Options, Forfeitures and Expirations in Period, Weighted Average Exercise Price Outstanding at end of period (in usd per share) Vested and expected to vest at end of period (in usd per share) Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Weighted Average Exercise Price Exercisable at end of period (in usd per share) Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Exercise Price Weighted-Average Remaining Contractual Term, Outstanding Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Remaining Contractual Term Weighted-Average Remaining Contractual Term, Vested and expected to vest Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Weighted Average Remaining Contractual Term Weighted-Average Remaining Contractual Term, Exercisable Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Remaining Contractual Term Aggregate Intrinsic Value, Outstanding Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Intrinsic Value Aggregate Intrinsic Value, Vested and expected to vest Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Aggregate Intrinsic Value Aggregate Intrinsic Value, Exercisable Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Intrinsic Value Current tax expense Current Income Tax Expense (Benefit) Deferred tax expense Deferred Income Tax Expense (Benefit) Banking and Thrift [Abstract] Required reserve balance Restricted Cash and Cash Equivalents Statement of Comprehensive Income [Abstract] Change in fair value of investment securities available for sale, net of tax of $(1,591), $826 and $(2,316), respectively Other Comprehensive Income (Loss), Unrealized Holding Gain (Loss) on Securities Arising During Period, Net of Tax Reclassification adjustment for net gain from sale of investment securities available for sale included in income, net of tax of $(29), $(2) and $(461), respectively Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Sale of Securities, Net of Tax Comprehensive income Comprehensive Income (Loss), Net of Tax, Attributable to Parent Changes in other real estate owned Other Real Estate [Roll Forward] Balance at the beginning of the year Other Real Estate Additions Other Real Estate, Additions Additions from acquisitions Noncash or Part Noncash Acquisition Other Real Estate Owned Noncash or part noncash acquisition other real estate owned. Proceeds from dispositions Other Real Estate, Disposals Gain on sale, net Gains (Losses) on Sales of Other Real Estate Valuation adjustment Other Real Estate, Valuation Adjustments Balance at the end of the year Retirement Benefits [Abstract] Schedule of Deferred Compensation Arrangement with Individual, Postretirement Benefits [Table] Schedule of Deferred Compensation Arrangement with Individual, Postretirement Benefits [Table] Plan Name [Axis] Plan Name [Axis] Plan Name [Domain] Plan Name [Domain] 401(k) Plan and Trust Salary Saving Plan Heritage Financial Corporation 401(k) Plan and Trust Salary Saving Plan [Member] Heritage Financial Corporation 401(k) Plan and Trust Salary Saving Plan [Member] 401(k) Plan and Trust Heritage Financial Corporation 401(k) Plan and Trust [Member] Heritage Financial Corporation 401(k) Plan and Trust [Member] Deferred Compensation Plan deferred compensation plan [Member] deferred compensation plan [Member] Balance Sheet Location [Axis] Balance Sheet Location [Axis] Balance Sheet Location [Domain] Balance Sheet Location [Domain] Accrued expenses and other liabilities Accrued Expenses and Other Liabilities [Member] Accrued Expenses and Other Liabilities [Member] Business Acquisition [Axis] Business Acquisition [Axis] Business Acquisition, Acquiree [Domain] Business Acquisition, Acquiree [Domain] Washington Banking Washington Banking [Member] Washington Banking [Member] Deferred Compensation Arrangement with Individual, Postretirement Benefits [Line Items] Deferred Compensation Arrangement with Individual, Postretirement Benefits [Line Items] Minimum service days required for eligibility under the plan Minimum Service Days Required for Eligibility Under Plan Minimum Service Days Required for Eligibility Under Plan Employer matching contribution, percent of employee's gross pay Defined Contribution Plan, Employer Matching Contribution, Percent of Employees' Gross Pay Maximum annual contributions per employee, percent Defined Contribution Plan, Maximum Annual Contributions Per Employee, Percent Percentage of employer contribution fully vested Percentage of Employer Contribution Fully Vested Percentage of Employer Contribution Fully Vested Defined contribution plan, employer matching contribution amount defined contribution plan, employer matching contribution amount defined contribution plan, employer matching contribution amount Minimum hours of service required for eligibility under the plan Minimum Hours of Service Required for Eligibility Under Plan Minimum Hours of Service Required for Eligibility Under Plan Minimum age required for eligibility under the plan Minimum Age Required for Eligibility Under Plan Minimum Age Required for Eligibility Under Plan Employer profit sharing contributions Defined Contribution Plan, Employer Contribution for Profit Sharing and Discretionary Defined Contribution Plan, Employer Contribution for Profit Sharing and Discretionary Compensation expense Deferred Compensation Arrangement with Individual, Compensation Expense Company's contributions Deferred Compensation Arrangement with Individual, Contributions by Employer Carrying value of obligation related to deferred compensation plan Deferred Compensation Arrangement with Individual, Recorded Liability Carrying value of obligation Liability for Future Policy Benefits, Life Salary Continuation Plan Salary Continuation Plan Salary Continuation Plan Salary Continuation Plan expense Salary Continuation Plan Expense Salary Continuation Plan Expense Changes in accumulated other comprehensive income (loss) Schedule of Accumulated Other Comprehensive Income (Loss) [Table Text Block] PCI Loans Purchase Credit Impaired Loans [Member] [Domain] Purchase Credit Impaired Loans [Member] [Domain] Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Accretable Yield Movement Schedule [Roll Forward] Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Accretable Yield Movement Schedule [Roll Forward] Balance at the beginning of the year Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Accretable Yield Accretion Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Accretable Yield, Accretion Disposal and other Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Accretable Yield, Disposals of Loans Change in accretable yield Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Accretable Yield, Reclassifications (to) from Nonaccretable Difference Balance at the end of the year Investments, Debt and Equity Securities [Abstract] Schedule of Available-for-sale Securities [Table] Schedule of Available-for-sale Securities [Table] Financial Instrument [Axis] Financial Instrument [Axis] Financial Instruments [Domain] Financial Instruments [Domain] U.S. Treasury and U.S. Government-sponsored agencies US Treasury and Government [Member] Municipal securities Municipal Bonds [Member] Residential mortgage-backed securities Residential Mortgage Backed Securities [Member] Commercial mortgage-backed securities Commercial Mortgage Backed Securities [Member] Collateralized loan obligations Collateralized Loan Obligations [Member] Corporate obligations Corporate Debt Securities [Member] Other securities Other Security Investments [Member] Schedule of Available-for-sale Securities [Line Items] Schedule of Available-for-sale Securities [Line Items] Amortized Cost Available-for-sale Debt Securities, Amortized Cost Basis Gross Unrealized Gains Available-for-sale Debt Securities, Accumulated Gross Unrealized Gain, before Tax Gross Unrealized Losses Available-for-sale Debt Securities, Accumulated Gross Unrealized Loss, before Tax Fair Value Available-for-sale Securities, Debt Securities Property, Plant and Equipment [Abstract] Property, Plant and Equipment [Table] Property, Plant and Equipment [Table] Property, Plant and Equipment, Type [Axis] Property, Plant and Equipment, Type [Axis] Property, Plant and Equipment, Type [Domain] Property, Plant and Equipment, Type [Domain] Land Land [Member] Buildings and building improvements Building and Building Improvements [Member] Furniture, fixtures and equipment Furniture and Fixtures [Member] Property, Plant and Equipment [Line Items] Property, Plant and Equipment [Line Items] Total premises and equipment Property, Plant and Equipment, Gross Less: Accumulated depreciation Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment Premises and equipment, net Property, Plant and Equipment, Net Depreciation Depreciation Business Combinations [Abstract] Schedule of Business Acquisitions, by Acquisition [Table] Schedule of Business Acquisitions, by Acquisition [Table] Puget Sound Puget Sound Bank [Member] Puget Sound Bank [Member] Premier Commercial Premier Commercial Bancorp [Member] Premier Commercial Bancorp [Member] Business Acquisition [Line Items] Business Acquisition [Line Items] Number of shares issued (in shares) Business Combination, Shares Of Common Stock Issued Of Acquired Entity Business Combination, Shares Of Common Stock Issued Of Acquired Entity Number of shares issued Business Acquisition, Equity Interest Issued or Issuable, Number of Shares Share price (in usd per share) Business Acquisition, Share Price Fair value of shares issued Business Acquisition, Equity Interest Issued or Issuable, Value Assigned Share price paid in cash (in usd per share) Business Acquisition, Share Price paid in Cash The cash paid per share as part of the consideration in a business combination Total consideration paid Business Combination, Consideration Transferred Total fair value of shares forfeited to pay applicable taxes Business Combination, Fair Value of Shares Issued in Merger but Forfeited to Pay Taxes Business Combination, Fair Value of Shares Issued in Merger but Forfeited to Pay Taxes Number of shares forfeited to pay applicable taxes (in shares) Business Combination, Shares Issued in Merger but Forfeited to Pay Taxes Business Combination, Shares Issued in Merger but Forfeited to Pay Taxes Acquisition-related costs Business Combination, Acquisition Related Costs Goodwill Goodwill, Acquired During Period Goodwill, purchase accounting adjustment Goodwill, Purchase Accounting Adjustments Schedule of Compliance with Regulatory Capital Requirements under Banking Regulations [Table] Schedule of Compliance with Regulatory Capital Requirements under Banking Regulations [Table] Legal Entity [Axis] Legal Entity [Axis] Entity [Domain] Entity [Domain] Heritage Bank Heritage Bank [Member] Heritage bank. Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items] Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items] Common Equity Tier One Capital Required for Capital Adequacy Common Equity Tier One Capital Required for Capital Adequacy Common Equity Tier One Capital Required for Capital Adequacy to Average Assets Common Equity Tier One Capital Required for Capital Adequacy to Average Assets Common Equity Tier One Capital Required for Capital Adequacy to Average Assets Common Equity Tier One Capital Required to be Well-Capitalized Common Equity Tier One Capital Required to be Well-Capitalized Common Equity Tier One Capital Required to be Well Capitalized to Average Assets Common Equity Tier One Capital Required to be Well Capitalized to Average Assets Common Equity Tier One Capital Required to be Well Capitalized to Average Assets Common Equity Tier One Capital Common Equity Tier One Capital Common Equity Tier One Capital to Average Assets Common Equity Tier One Capital to Average Assets Common Equity Tier One Capital to Average Assets Tier One Leverage Capital Required for Capital Adequacy Tier One Leverage Capital Required for Capital Adequacy Tier One Leverage Capital Required for Capital Adequacy to Average Assets Tier One Leverage Capital Required for Capital Adequacy to Average Assets Tier One Leverage Capital Required to be Well Capitalized Tier One Leverage Capital Required to be Well Capitalized Tier One Leverage Capital Required to be Well Capitalized to Average Assets Tier One Leverage Capital Required to be Well Capitalized to Average Assets Tier One Leverage Capital Tier One Leverage Capital Tier One Leverage Capital to Average Assets Tier One Leverage Capital to Average Assets Tier One Risk Based Capital Required for Capital Adequacy Tier One Risk Based Capital Required for Capital Adequacy Tier One Risk Based Capital Required for Capital Adequacy to Risk Weighted Assets Tier One Risk Based Capital Required for Capital Adequacy to Risk Weighted Assets Tier One Risk Based Capital Required to be Well Capitalized Tier One Risk Based Capital Required to be Well Capitalized Tier One Risk Based Capital Required to be Well Capitalized to Risk Weighted Assets Tier One Risk Based Capital Required to be Well Capitalized to Risk Weighted Assets Tier One Risk Based Capital Tier One Risk Based Capital Tier One Risk Based Capital to Risk Weighted Assets Tier One Risk Based Capital to Risk Weighted Assets Capital Required for Capital Adequacy Capital Required for Capital Adequacy Capital Required for Capital Adequacy to Risk Weighted Assets Capital Required for Capital Adequacy to Risk Weighted Assets Capital Required to be Well Capitalized Capital Required to be Well Capitalized Capital Required to be Well Capitalized to Risk Weighted Assets Capital Required to be Well Capitalized to Risk Weighted Assets Capital Capital Capital to Risk Weighted Assets Capital to Risk Weighted Assets Capital conservation buffer, percentage Capital Conservation Buffer, Percentage Capital Conservation Buffer, Percentage Investment Securities Investments in Debt and Marketable Equity Securities (and Certain Trading Assets) Disclosure [Text Block] Schedule of Impaired Financing Receivable [Table] Schedule of Impaired Financing Receivable [Table] Financing Receivable, Impaired [Line Items] Financing Receivable, Impaired [Line Items] Outstanding Principal Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Outstanding Balance Recorded Investment Certain Loans Acquired In Transfer Not Accounted For As Debt Securities Carrying Amount The recorded balance after any applicable reductions (i.e. outstanding balance net of unamortized accretable yield). This relates to loans not accounted for debt securities with evidence of deterioration of credit quality since origination that were acquired by completion of a transfer for which it is probable, at acquisition, that the investor will be unable to collect all contractually required payments receivable. Schedule of stock option activity Share-based Compensation, Activity [Table Text Block] Schedule of restricted stock award activity Schedule of Share-based Compensation, Restricted Stock Units Award Activity [Table Text Block] Schedule of assumptions of PRSUs granted Schedule of Share-based Payment Award, Equity Instruments Other than Options, Valuation Assumptions [Table Text Block] Schedule of Share-based Payment Award, Equity Instruments Other than Options, Valuation Assumptions [Table Text Block] Summary of RSU activity Schedule of Nonvested Restricted Stock Units Activity [Table Text Block] Recorded Investment With No Specific Valuation Allowance Impaired Financing Receivable, with No Related Allowance, Recorded Investment Recorded Investment With Specific Valuation Allowance Impaired Financing Receivable, with Related Allowance, Recorded Investment Total Recorded Investment Impaired Financing Receivable, Recorded Investment Unpaid Contractual Principal Balance Impaired Financing Receivable, Unpaid Principal Balance Related Specific Valuation Allowance Impaired Financing Receivable, Related Allowance Unallocated Unallocated [Member] Unallocated. Allowance for Loan Losses Disaggregated: Accounts, Notes, Loans and Financing Receivable, Gross, Allowance, and Net [Abstract] Loans Individually Evaluated for Impairment Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment Loans Collectively Evaluated for Impairment Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment PCI Loans Certain Loans and Debt Securities Acquired in Transfer, Allowance for Credit Losses Due to Subsequent Impairment Total Allowance for Loan Losses Loan Receivables, Disaggregated: Financing Receivable, Additional Disclosures [Abstract] Loans Individually Evaluated for Impairment Financing Receivable, Individually Evaluated for Impairment Loans Collectively Evaluated for Impairment Financing Receivable, Collectively Evaluated for Impairment PCI Loans Total Gross Loans Receivable Amount Deposits Liabilities, Balance Sheet, Reported Amounts [Abstract] Noninterest demand deposits Noninterest-bearing Domestic Deposit, Demand Interest bearing demand deposits Interest-bearing Domestic Deposit, Demand Money market accounts Interest-bearing Domestic Deposit, Money Market Savings accounts Interest-bearing Domestic Deposit, Savings Total non-maturity deposits Interest-bearing Domestic Deposit, Time Deposits Certificate of deposit accounts Interest-bearing Domestic Deposit, Certificates of Deposits Total deposits Deposits Percent Percentage of Interest-bearing Domestic Deposit Liabilities to Deposit Liabilities [Abstract] Noninterest demand deposits (as a percent) Percentage Of Noninterest-Bearing Domestic Deposit, Demand Percentage Of Noninterest-Bearing Domestic Deposit, Demand Interest bearing demand deposits (as a percent) Percentage of Interest-bearing Domestic Deposits to Deposits, Demand Money market accounts (as a percent) Percentage of Interest-bearing Domestic Deposits to Deposits, Money Market Savings accounts (as a percent) Percentage of Interest-bearing Domestic Deposits to Deposits, Savings Total non-maturity deposits (as a percent) Percentage of Interest-bearing Domestic Deposits to Deposits, Time Deposits Certificate of deposit accounts (as a percent) Percentage of Interest-bearing Domestic Deposits to Deposits, Certificates of Deposit Total deposits (as a percent) Percentage of Interest-bearing Domestic Deposits to Deposits Organization, Consolidation and Presentation of Financial Statements [Abstract] Description of Business, Basis of Presentation and Significant Accounting Policies and Recently Issued Accounting Pronouncements Organization, Consolidation and Presentation of Financial Statements Disclosure [Text Block] Preliminary fair value estimates of assets acquired and liabilities assumed and adjustments Schedule of Recognized Identified Assets Acquired and Liabilities Assumed [Table Text Block] Summary of results of operations of acquired business Business Combination, Results Of Operations Of Acquired Business [Table Text Block] Business Combination, Results Of Operations Of Acquired Business [Table Text Block] Unaudited pro forma information Business Acquisition, Pro Forma Information [Table Text Block] Description of Business Description of Business [Policy Text Block] The entire disclosure for the business description and basis of presentation concepts. Business description describes the nature and type of organization including but not limited to organizational structure as may be applicable to holding companies, parent and subsidiary relationships, business divisions, business units, business segments, affiliates and information about significant ownership of the reporting entity. Basis of Presentation Basis of Accounting, Policy [Policy Text Block] Reclassifications Reclassification, Policy [Policy Text Block] Cash and Cash Equivalents Cash and Cash Equivalents, Policy [Policy Text Block] Investment Securities Marketable Securities, Policy [Policy Text Block] Loans Held for Sale Finance, Loan and Lease Receivables, Held-for-sale, Policy [Policy Text Block] Loans Receivable and Loan Commitments Loans Receivable and Loan Commitments Policy [Policy Text Block] Loans Receivable and Loan Commitments Policy [Policy Text Block] Loan Fees and Costs Deferred Charges, Policy [Policy Text Block] Allowance for Loan Losses Loans and Leases Receivable, Allowance for Loan Losses Policy [Policy Text Block] Mortgage Banking Operations Loans and Leases Receivable, Mortgage Banking Activities, Policy [Policy Text Block] Other Real Estate Owned Real Estate, Policy [Policy Text Block] Premises and Equipment Property, Plant and Equipment, Policy [Policy Text Block] Bank Owned Life Insurance Life Insurance, Corporate or Bank Owned Policy [Policy Text Block] Life Insurance, Corporate or Bank Owned Policy [Policy Text Block] Other Intangible Assets Goodwill and Intangible Assets, Intangible Assets, Policy [Policy Text Block] Goodwill Goodwill and Intangible Assets, Goodwill, Policy [Policy Text Block] Income Taxes Income Tax, Policy [Policy Text Block] Stock-Based Compensation and Deferred Compensation Plans Compensation Related Costs, Policy [Policy Text Block] Earnings per Share Earnings Per Share, Policy [Policy Text Block] Derivative Financial Instruments Derivatives, Policy [Policy Text Block] Operating Segments Segment Reporting, Policy [Policy Text Block] Revenue from Contract with Customers Revenue From Contract With Customer [Policy Text Block] Revenue From Contract With Customer [Policy Text Block] Recently Issued Accounting Pronouncements New Accounting Pronouncements, Policy [Policy Text Block] Number of operating segments Number of Operating Segments Concentration of loans greater than 10% Concentration Risk Percentage Greater than Ten Percent Concentration risk percentage greater than ten percent. Percentage of concentrations of loans in any industry (in excess of 10%) (percent) Concentration Risk, Percentage Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table] Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table] Award Type [Axis] Award Type [Axis] Equity Award [Domain] Equity Award [Domain] RSU Restricted Stock Units (RSUs) [Member] Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Shares Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward] Nonvested at beginning of period (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number Granted (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period Vested (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period Forfeited (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeited in Period Nonvested at end of period (in shares) Weighted-Average Grant Date Fair Value Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract] Nonvested at beginning of period (in usd per share) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value Granted (in usd per share) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value Vested (in usd per share) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Weighted Average Grant Date Fair Value Forfeited (in usd per share) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeitures, Weighted Average Grant Date Fair Value Nonvested at end of period (in usd per share) Condensed Income Statement [Table] Condensed Income Statement [Table] Condensed Income Statements, Captions [Line Items] Condensed Income Statements, Captions [Line Items] Interest and dividends on interest earning deposits and other assets Interest Income, Deposits with Financial Institutions Total interest income Interest and Dividend Income, Operating Junior subordinated debentures Interest Expense, Junior Subordinated Debentures Total interest expense Interest Expense Net interest income Interest Income (Expense), Net Dividends from subsidiary bank Dividend Income, Operating Equity in undistributed income of subsidiary bank Other income Noninterest Income, Other Total noninterest income Noninterest Income Professional services Professional Fees Other expense Other Noninterest Expense Total noninterest expense Noninterest Expense Income before income taxes Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest Income tax expense Net income Restricted Stock Awards Restricted Stock [Member] Vesting [Axis] Vesting [Axis] Vesting [Domain] Vesting [Domain] Award 1 Share-based Compensation Award, Tranche One [Member] Award 2 Share-based Compensation Award, Tranche Two [Member] Vesting period Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period Compensation expense Allocated Share-based Compensation Expense Tax benefit Employee Service Share-based Compensation, Tax Benefit from Compensation Expense Total unrecognized compensation expense Employee Service Share-based Compensation, Nonvested Awards, Compensation Not yet Recognized, Share-based Awards Other than Options Weighted average, recognition period Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition Restricted stock awards issued, net of forfeitures Stock Issued During Period, Value, Restricted Stock Award, Gross Quarterly Financial Information Disclosure [Abstract] Selected Quarterly Financial Data (Unaudited) Quarterly Financial Information [Text Block] Schedule of allowance for loan losses on the basis of impairment method Allowance for Loan and Lease Losses [Roll Forward] Balance at the beginning of the year Charge-offs Allowance for Loan and Lease Losses, Write-offs Recoveries Allowance for Loan and Lease Loss, Recovery of Bad Debts Provision for loan losses Provision for Loan and Lease Losses Balance at the end of the year Commitments and Contingencies Disclosure [Abstract] 2019 Operating Leases, Future Minimum Payments Due, Next Twelve Months 2020 Operating Leases, Future Minimum Payments, Due in Two Years 2021 Operating Leases, Future Minimum Payments, Due in Three Years 2022 Operating Leases, Future Minimum Payments, Due in Four Years 2023 Operating Leases, Future Minimum Payments, Due in Five Years Thereafter Operating Leases, Future Minimum Payments, Due Thereafter Future minimum annual rental commitments Operating Leases, Future Minimum Payments Due Useful lives Property, Plant and Equipment, Useful Life Schedule of Financing Receivable, Troubled Debt Restructurings [Table] Schedule of Financing Receivable, Troubled Debt Restructurings [Table] Troubled Debt Restructured Loans Troubled Debt Restructured Loans [Member] Troubled debt restructured loans. Loan Restructuring Modification [Axis] Loan Restructuring Modification [Axis] Loan Restructuring Modification [Domain] Loan Restructuring Modification [Domain] Modified during the year Modified during the year [Member] Modified during the year [Member] Modified subsequently Finance Receivable Modified Subsequent Default [Member] Finance Receivable Modified Subsequent Default [Member] Financing Receivables, Period Past Due [Axis] Financing Receivables, Period Past Due [Axis] Financing Receivables, Period Past Due [Domain] Financing Receivables, Period Past Due [Domain] Past modified maturity date Past Modified Maturity Date [Member] Past Modified Maturity Date [Member] 30-89 days past due Financing Receivables, 30 to 89 Days Past Due [Member] Financing Receivables, 30 to 89 Days Past Due [Member] Financing Receivable, Modifications [Line Items] Financing Receivable, Modifications [Line Items] Related specific valuation allowance for TDRs Number of contracts modified that subsequently defaulted Financing Receivable, Modifications, Subsequent Default, Number of Contracts Loans modified during the previous twelve months and subsequently defaulted Financing Receivable, Modifications, Subsequent Default, Recorded Investment Debt Disclosure [Abstract] Other Borrowings Other Borrowings [Text Block] Other Borrowings [Text Block] New Accounting Pronouncements or Change in Accounting Principle [Table] New Accounting Pronouncements or Change in Accounting Principle [Table] Adjustments for New Accounting Pronouncements [Axis] Adjustments for New Accounting Pronouncements [Axis] Type of Adoption [Domain] Type of Adoption [Domain] ASU 2016-01 Accounting Standards Update 2016-01 [Member] ASU 2016-02 Accounting Standards Update 2016-02 [Member] ASU 2018-02 Accounting Standards Update 2018-02 [Member] Accounting Standards Update 2018-02 [Member] Subsequent Event Type [Axis] Subsequent Event Type [Axis] Subsequent Event Type [Domain] Subsequent Event Type [Domain] Subsequent Event Subsequent Event [Member] New Accounting Pronouncements or Change in Accounting Principle [Line Items] New Accounting Pronouncements or Change in Accounting Principle [Line Items] Cumulative effect of new accounting principle Operating lease assets Operating Lease, Right-of-Use Asset Operating lease liabilities Operating Lease, Liability Reclassification of stranded tax effects from accumulated other comprehensive loss to retained earnings Tax Cuts And Jobs Act Of 2017, Reclassification From AOCI To Retained Earnings, Tax Effect Tax Cuts And Jobs Act Of 2017, Reclassification From AOCI To Retained Earnings, Tax Effect SBA Loans [Table] SBA Loans [Table] SBA Loans [Table] Receivable Type [Axis] Receivable Type [Axis] Receivable [Domain] Receivable [Domain] SBA Loans SBA Loans [Member] SBA Loans [Member] SBA Loans [Line Items] SBA Loans [Line Items] [Line Items] for SBA Loans [Table] SBA loans serviced for others with participating interest, gross loan balance Participating Loans Borrower Obligations Amount The aggregate amount of the participating loan obligation at the end of the accounting period. SBA loans serviced for others with participating interest, participation balance owned by Bank Transfer of Financial Assets Accounted for as Sales, Amount Derecognized Servicing fee income and fees from SBA loans serviced for others Fees and Commissions, Mortgage Banking and Servicing Derivative [Table] Derivative [Table] Hedging Designation [Axis] Hedging Designation [Axis] Hedging Designation [Domain] Hedging Designation [Domain] Non-hedging interest rate derivatives Not Designated as Hedging Instrument [Member] Derivative Instrument [Axis] Derivative Instrument [Axis] Derivative Contract [Domain] Derivative Contract [Domain] Interest rate swaps Interest Rate Swap [Member] Prepaid expenses and other assets Prepaid Expenses and Other Current Assets [Member] Derivative [Line Items] Derivative [Line Items] Notional Amounts - Interest rate swaps with customer Derivative Asset, Notional Amount Notional Amounts - Interest rate swap with third party Derivative Liability, Notional Amount Estimated Fair Value - Interest rate swaps with customer Derivative Asset, Fair Value, Gross Asset Estimated Fair Value - Interest rate swap with third party Derivative Liability, Fair Value, Gross Liability Statement of Financial Position [Abstract] Preferred stock, no par value (in usd per share) Preferred Stock, Par or Stated Value Per Share Preferred stock, shares authorized Preferred Stock, Shares Authorized Preferred stock, shares issued Preferred Stock, Shares Issued Preferred stock, shares outstanding Preferred Stock, Shares Outstanding Common stock, no par value (in usd per share) Common Stock, No Par Value Common stock, shares authorized Common Stock, Shares Authorized Common stock, shares issued Common Stock, Shares, Issued Common stock, shares outstanding Common Stock, Shares, Outstanding Schedule of Variable Interest Entities [Table] Schedule of Variable Interest Entities [Table] Scenario [Axis] Scenario [Axis] Scenario, Unspecified [Domain] Scenario, Unspecified [Domain] Forecast Scenario, Forecast [Member] Subsidiaries Subsidiaries [Member] Tax Credit Carryforward [Axis] Tax Credit Carryforward [Axis] Tax Credit Carryforward, Name [Domain] Tax Credit Carryforward, Name [Domain] Investment Tax Credit Carryforward Investment Tax Credit Carryforward [Member] Tax Period [Axis] Tax Period [Axis] Tax Period [Domain] Tax Period [Domain] 2020 Twenty Twenty [Member] Twenty Twenty [Member] Variable Interest Entity [Line Items] Variable Interest Entity [Line Items] Number of equity investments in LIHTCs Variable Interest Entity Number of Investments Variable Interest Entity Number of Investments Investments in unconsolidated LIHTCs Investments in Affordable Housing Limited Entities Investments in Affordable Housing Limited Entities Tax benefits Affordable Housing Tax Credits and Other Tax Benefits, Amount Commitments Qualified Affordable Housing Project Investments, Commitment Qualified Affordable Housing Project Investments, future commitment Qualified Affordable Housing Project Investments, Future Commitment Qualified Affordable Housing Project Investments, Future Commitment Impairment losses on LIHTC investments Affordable Housing Project Investment, Write-down, Amount Qualified Equity Investments Qualified Equity Investments Qualified Equity Investments Number of tranches Number of Tranches Number of Tranches Gross tax credits related to the Company's CDEs Tax Credit carryforward, Amount Subject to Expiration Tax Credit carryforward, Amount Subject to Expiration Percentage of tranche required to fund to claim the entire tax credit Tax Credit Carryforward, Required Funding Percentage Tax Credit Carryforward, Required Funding Percentage Carrying value of NMTC Investment in Certified Development Entities Investment in Certified Development Entities Investment income Income (Loss) from Affordable Housing Projects, Equity Method Investments Document and Entity Information [Abstract] Document and entity information. Entity Registrant Name Entity Registrant Name Entity Central Index Key Entity Central Index Key Document Type Document Type Document Period End Date Document Period End Date Amendment Flag Amendment Flag Document Fiscal Year Focus Document Fiscal Year Focus Document Fiscal Period Focus Document Fiscal Period Focus Current Fiscal Year End Date Current Fiscal Year End Date Entity Filer Category Entity Filer Category Entity Small Business Entity Small Business Entity Small Business Entity Emerging Growth Company Entity Emerging Growth Company Entity Emerging Growth Company Entity Shell Company Entity Shell Company Entity Shell Company Entity Common Stock, Shares Outstanding Entity Common Stock, Shares Outstanding Entity Public Float Entity Public Float Entity Well-known Seasoned Issuer Entity Well-known Seasoned Issuer Entity Voluntary Filers Entity Voluntary Filers Entity Current Reporting Status Entity Current Reporting Status Net interest income Business Acquisition, Pro Forma Revenue Net income Business Acquisition, Pro Forma Net Income (Loss) Basic earnings per common share (in usd per share) Business Acquisition, Pro Forma Earnings Per Share, Basic Diluted earnings per common share (in usd per share) Business Acquisition, Pro Forma Earnings Per Share, Diluted Goodwill and Other Intangible Assets Goodwill Disclosure [Text Block] Changes in other real estate owned Other Real Estate, Roll Forward [Table Text Block] Disclosure of Repurchase Agreements [Abstract] Repurchase agreement obligation by class of collateral pledged Schedule of Repurchase Agreements [Table Text Block] Stockholders' Equity Stockholders' Equity Note Disclosure [Text Block] ASSETS Cash on hand and in banks Cash and Due from Banks Interest earning deposits Interest-bearing Deposits in Banks and Other Financial Institutions Cash and cash equivalents Cash and Cash Equivalents, at Carrying Value Investment securities available for sale, at fair value Available-for-sale Securities Loans held for sale Loans Receivable Held-for-sale, Net, Not Part of Disposal Group, Mortgage Loans receivable, net Other real estate owned Premises and equipment, net Federal Home Loan Bank stock, at cost Federal Home Loan Bank Stock Bank owned life insurance Bank Owned Life Insurance Accrued interest receivable Interest Receivable Prepaid expenses and other assets Prepaid Expense and Other Assets Other intangible assets, net Intangible Assets, Net (Excluding Goodwill) Goodwill Goodwill LIABILITIES AND STOCKHOLDERS' EQUITY Deposits Federal Home Loan Bank advances Long-term Federal Home Loan Bank Advances Junior subordinated debentures Securities sold under agreement to repurchase Securities Sold under Agreements to Repurchase Accrued expenses and other liabilities Total liabilities Liabilities Stockholders’ equity: Stockholders' Equity Attributable to Parent [Abstract] Preferred stock, no par value, 2,500,000 shares authorized; no shares issued and outstanding at December 31, 2018 and 2017 Preferred Stock, Value, Issued Common stock, no par value, 50,000,000 shares authorized; 36,874,055 and 29,927,746 shares issued and outstanding at December 31, 2018 and 2017, respectively Common Stock, Value, Issued Retained earnings Retained Earnings (Accumulated Deficit) Accumulated other comprehensive loss, net Accumulated Other Comprehensive Income (Loss), Net of Tax Total stockholders’ equity Securities classified as trading Trading Securities Securities classified as held to maturity Held-to-maturity Securities OTTI, unrealized losses Other than Temporary Impairment Losses, Investments, Portion Recognized in Earnings, Net, Held-to-maturity Securities Heritage Financial Corporation (Parent Company Only) Condensed Financial Information of Parent Company Only Disclosure [Text Block] Fair Value, by Balance Sheet Grouping [Table] Fair Value, by Balance Sheet Grouping [Table] Recurring Fair Value, Measurements, Recurring [Member] Assets Assets, Fair Value Disclosure [Abstract] Derivative assets - interest rate swaps Liabilities Liabilities, Fair Value Disclosure [Abstract] Derivative liabilities - interest rate swaps Premier Merger Puget Sound Merger Premier and Puget Mergers Premier And Puget Mergers [Member] Premier And Puget Mergers [Member] Interest income: Interest and fees on loans Interest and Fee Income, Loans and Leases Interest income: Interest and fees on investments Interest Income, Securities, Operating, Taxable Interest income: Other interest earning assets Other Interest and Dividend Income Interest expense Provision for loan losses for loans Noninterest income Noninterest expense Accretion of discount on purchased loans Investment Income, Amortization of Discount Mortgage Loans on Real Estate Schedule [Table] Mortgage Loans on Real Estate Schedule [Table] Mortgage Loans on Real Estate [Line Items] Mortgage Loans on Real Estate [Line Items] Carrying amount of other real estate owned from foreclosure Other Real Estate, Foreclosed Assets, and Repossessed Assets Mortgage loans secured by residential real estate properties Mortgage Loans in Process of Foreclosure, Amount Line of Credit Facility [Table] Line of Credit Facility [Table] Credit Facility [Axis] Credit Facility [Axis] Credit Facility [Domain] Credit Facility [Domain] Federal Reserve Bank Advances Federal Reserve Bank Advances [Member] Line of Credit Facility [Line Items] Line of Credit Facility [Line Items] Credit facility, maximum borrowing capacity Line of Credit Facility, Maximum Borrowing Capacity Borrowings outstanding Line of Credit Facility Line of Credit Facility Fair Value Inputs, Assets, Quantitative Information [Table] Fair Value Inputs, Assets, Quantitative Information [Table] Measurement Input Type [Axis] Measurement Input Type [Axis] Measurement Input Type [Axis] Measurement Input Type [Domain] Measurement Input Type [Domain] [Domain] for Measurement Input Type [Axis] Comparability Adjustment Measurement Input, Comparability Adjustment [Member] Measurement Input, Comparability Adjustment [Member] Weighted Average Weighted Average [Member] Fair Value Inputs, Assets, Quantitative Information [Line Items] Fair Value Inputs, Assets, Quantitative Information [Line Items] Fair value measurements for financial instruments measured at fair value on a non-recurring basis Fair Value Inputs, Quantitative Information [Abstract] Impaired loans Range of Inputs Impaired Loans, Measurement Input Impaired Loans, Measurement Input Employee Benefit Plans Compensation and Employee Benefit Plans [Text Block] Credit facility with the FHLB Federal Home Loan Bank, Advances, General Debt Obligations, Maximum Amount Available Advances outstanding Federal Home Loan Bank, Advances, Branch of FHLB Bank, Amount of Advances FHLB Advances: Advances from Federal Home Loan Banks [Abstract] Average balance during the year Federal Home Loan Bank, Advances, Activity for Year, Average Balance of Agreements Outstanding Maximum month-end balance during the year Federal Home Loan Bank, Advances, Activity for Year, Maximum Outstanding at any Month End Weighted average rate during the year Federal Home Loan Bank, Advances, Activity for Year, Average Interest Rate for Year Weighted average rate at the end of year Federal Home Loan Bank, Advances, Activity for Year, Average Interest Rate at Period End Federal Home Loan Bank, Advances [Table] Federal Home Loan Bank, Advances [Table] Federal Home Loan Bank, Advances [Line Items] Federal Home Loan Bank, Advances [Line Items] Unencumbered collateral in amount equal to varying percentages Unencumbered collateral in amount equal to varying percentages Unencumbered collateral in amount equal to varying percentages Reconciliation of available for sale securities Schedule of Available-for-sale Securities Reconciliation [Table Text Block] Schedule of securities available for sale Available-for-sale Securities [Table Text Block] Schedule of fair value and unrealized losses of available for sale investment securities Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value [Table Text Block] Gross realized gains and losses on sale of securities available for sale Schedule of Realized Gain (Loss) [Table Text Block] Scheduled of amortized cost and fair value of securities pledged as collateral Schedule of Financial Instruments Owned and Pledged as Collateral [Table Text Block] Schedule of FHLB advances Federal Home Loan Bank, Advances [Table Text Block] Loans and Leases Receivable Disclosure [Table] Loans and Leases Receivable Disclosure [Table] Loans and Leases Receivable Disclosure [Line Items] Loans and Leases Receivable Disclosure [Line Items] One-to-four family residential loans: Mortgage Banking [Abstract] Originated Payments for Origination of Mortgage Loans Held-for-sale Sold Proceeds from Sale of Mortgage Loans Held-for-sale Gains on sales of loans, net Gain (Loss) on Sale of Mortgage Loans Contractual amounts of commitments to sell and fund with off-balance sheet risk: Contractual Amounts of Commitments [Abstract] Contractual Amounts of Commitments [Abstract] Commitments to sell mortgage loans Loans and Leases Receivable, Commitments to Purchase or Sell Commitments to fund mortgage loans (at interest rates approximating market rates) for portfolio or for sale: Commitments to Fund Mortgage Loans [Abstract] Commitments to Fund Mortgage Loans [Abstract] Fixed rate Loans and Leases Receivable, Commitments, Fixed Rates Variable or adjustable rate Loans and Leases Receivable, Commitments, Variable Rates Total commitments to fund mortgage loans Loans and Leases Receivable, Total Commitments to Purchase or Sell Loans and Leases Receivable, Total Commitments to Purchase or Sell Results of operations on a quarterly basis Quarterly Financial Information [Table Text Block] Repurchase Agreements Disclosure of Repurchase Agreements [Text Block] Disclosure of Repurchase Agreements [Text Block] Statement of Cash Flows [Abstract] Depreciation of premises and equipment, amortization of securities available for sale, and amortization of discount of junior subordinated debentures Depreciation, Amortization and Accretion, Net Changes in net deferred loan costs, net of amortization Amortization of Deferred Loan Origination Fees, Net Net change in accrued interest receivable, prepaid expenses and other assets, accrued expenses and other liabilities Net Change in Accrued Interest Receivable, Prepaid Expenses and Other Assets, Accrued Expenses and Other Liabilities Net change in accrued interest receivable, prepaid expenses and other assets, accrued expenses and other liabilities. Stock-based compensation expense Net excess tax benefit from exercise of stock-based compensation Employee Service Share-based Compensation, Tax Benefit Realized from Exercise of Stock Options and Restricted and Unrestricted Stock Employee Service Share-based Compensation, Tax Benefit Realized from Exercise of Stock Options and Restricted and Unrestricted Stock Amortization of intangible assets Amortization of Intangible Assets Origination of loans held for sale Payments for Origination and Purchases of Loans Held-for-sale Proceeds from sale of loans Proceeds from Sale of Loans Held-for-sale Earnings on bank owned life insurance Bank Owned Life Insurance Income Valuation adjustment on other real estate owned Gain on sale of loans, net Gain (Loss) on Sale of Loans and Leases Gain on sale of investment securities, net Gain (Loss) on Sale of Investments Gain on sale of assets held for sale Gain (Loss) of Assets Held for Sale Gain (Loss) of Assets Held for Sale Loss on sale of other real estate owned Impairment of assets held for sale Impairment of Long-Lived Assets to be Disposed of Loss on sale or write-off of furniture, equipment and leasehold improvements Write off of leasehold improvements due to lease termination Write off of leasehold improvements due to lease termination Loans originated, net of principal payments Payments for (Proceeds from) Loans and Leases Maturities of other interest earning deposits Proceeds from Sale and Maturity of Other Investments Maturities, calls and payments of investment securities available for sale Proceeds from Maturities, Prepayments and Calls of Available-for-sale Securities Purchase of investment securities available for sale Payments to Acquire Available-for-sale Securities Purchase of premises and equipment Payments to Acquire Property, Plant, and Equipment Proceeds from sales of other loans Proceeds from Sales of Assets, Investing Activities Proceeds from sales of other real estate owned Proceeds from Sale of Foreclosed Assets Proceeds from sales of investment securities available for sale Proceeds from Sale of Available-for-sale Securities Proceeds from sales of assets held for sale Proceeds from Sale of Assets Held for Sale Proceeds from Sale of Assets Held for Sale Proceeds from redemption of Federal Home Loan Bank stock Payments for (Proceeds from) Federal Home Loan Bank Stock Purchases of Federal Home Loan Bank stock Payments to Acquire Federal Home Loan Bank Stock Proceeds from sales of premises and equipment Proceeds from Sale of Property, Plant, and Equipment Purchase of bank owned life insurance Purchase bank owned life insurance Purchase bank owned life insurance Proceeds from BOLI death benefit Proceeds from Life Insurance Policy Capital contributions to low-income housing tax credit partnerships and new market tax credit partnerships, net Change in low income tax housing tax credit partnership Change in low income tax housing tax credit partnership Net increase in deposits Increase (Decrease) in Deposits Federal Home Loan Bank advances Increase (Decrease) in Loans to Federal Home Loan Banks Repayments of Federal Home Loan Bank advances Repayments of Debt Common stock cash dividends paid Net (decrease)/increase in securities sold under agreement to repurchase Increase (Decrease) in Receivables under Repurchase Agreements Proceeds from exercise of stock options Net excess tax benefit from exercise of stock-based compensation Repurchase of common stock Cash and cash equivalents at beginning of year Cash and cash equivalents at end of year Supplemental disclosures of cash flow information: Cash paid for interest Interest Paid, Net Cash paid for income taxes Income Taxes Paid, Net Supplemental non-cash disclosures of cash flow information: Cash Flow, Noncash Investing and Financing Activities Disclosure [Abstract] Transfers of loans receivable to other real estate owned Real Estate Owned, Transfer to Real Estate Owned Transfers of properties held for sale recorded in premises and equipment, net to prepaid expenses and other assets Transfer of Property and Equipment to Prepaid Expenses and Other Assets Held-for-sale Transfer of Property and Equipment to Prepaid Expenses and Other Assets Held-for-sale Transfer of BOLI to prepaid expenses and other assets Transfer of Bank Owned Life Insurance To Prepaid Expenses And Other Assets Transfer of Bank Owned Life Insurance To Prepaid Expenses And Other Assets Investment in low income housing tax credit partnership and related funding commitment Investment in low income housing tax partnership Investment in low income housing tax partnership Business Combinations: Assets acquired (liabilities assumed) in acquisitions: Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net [Abstract] Investment securities available for sale Noncash or Part Noncash Acquisition Investment Available for Sale Noncash or part noncash acquisition investment available for sale. Loans receivable Noncash or Part Noncash Acquisition Purchased Non Covered Loans Receivable Noncash or part noncash acquisition purchased non covered loans receivable. Other real estate owned Premises and equipment Noncash or Part Noncash Acquisition, Fixed Assets Acquired Federal Home Loan Bank stock Noncash or Part Noncash Acquisition Accounts FHLB Stock Acquired Noncash or part noncash acquisition accounts FHLB stock acquired. Accrued interest receivable Noncash or Part Noncash Acquisition, Accounts Receivable Acquired Bank owned life insurance Noncash or Part Noncash, Bank Owned Life Insurance acquired Noncash or Part Noncash, Bank Owned Life Insurance acquired Prepaid expenses and other assets Noncash or Part Noncash Acquisition, Other Assets Acquired Other intangible assets Noncash or Part Noncash Acquisition, Intangible Assets Acquired Deposits Noncash or Part Noncash Acquisition Deposits Liability Noncash or part noncash acquisition deposits liability. Federal Home Loan Bank advances Noncash or Part Noncash Acquisition, Debt Assumed Securities sold under agreement to repurchase noncash or part noncash acquisition, securities sold under agreements to repurchase Noncash or Part Noncash Acquisition, Securities Sold Under Agreements to Repurchase Accrued expenses and other liabilities Noncash or Part Noncash Acquisition, Other Liabilities Assumed Accumulated Other Comprehensive Loss Comprehensive Income (Loss) Note [Text Block] Fair value assets transfers between level 1 and level 2 transfer amount Fair Value Assets Transfers Between Level 1 and Level 2 Transfers Amount Fair value assets transfers between level 1 and level 2 transfers amount. Loans and Leases Receivable Disclosure [Abstract] Schedule of loans receivable Schedule of Accounts, Notes, Loans and Financing Receivable [Table Text Block] Loans receivable by credit quality indicator Financing Receivable Credit Quality Indicators [Table Text Block] Schedule of nonaccrual loans Schedule of Financing Receivables, Non Accrual Status [Table Text Block] Past due financing receivables Past Due Financing Receivables [Table Text Block] Schedule of impaired loans, including restructured Impaired Financing Receivables [Table Text Block] Schedule of average recorded investment impaired loans including restructuring loans Schedule of Average Recorded Investment Impaired Loans Including Restructuring Loans [Table Text Block] Schedule of average recorded investment impaired loans including restructuring loans. Recorded investment balance and related allowance for loan losses of accruing and non-accruing TDRs Troubled Debt Restructurings of Financing Receivables on Basis of Accruing and Non Accruing [Table Text Block] Troubled debt restructurings of financing receivables on basis of accruing and non accruing. Troubled debt restructurings on financing receivables Troubled Debt Restructurings on Financing Receivables [Table Text Block] Troubled debt restructuring loans, subsequently defaulted Troubled Debt Restructurings Loans Subsequently Defaulted [Table Text Block] Troubled debt restructurings loans subsequently defaulted. Purchased impaired loans Schedule of Financing Receivables Loans Acquired with Credit Deterioration [Table Text Block] Schedule of financing receivables loans acquired with credit deterioration. Schedule of impaired purchased loans accretable yield Schedule of Impaired Purchased Loans Accretable Yield [Table Text Block] Schedule of impaired purchased loans accretable yield. Activity in related party loans Schedule of Related Party Transactions [Table Text Block] Mortgage banking activities Loans and Leases Receivable, Mortgage Banking Activities [Table Text Block] Loans and Leases Receivable, Mortgage Banking Activities [Table Text Block] Contractual amounts of commitments to sell and fund with off-balance sheet risk Contractual Amounts of Commitments with Off-balance Sheet Risk [Table Text Block] Contractual Amounts of Commitments with Off-balance Sheet Risk [Table Text Block] Details of SBNA loans serviced Summary of Servicing of Financial Assets [Table Text Block] Summary of Servicing of Financial Assets [Table Text Block] Number of Contracts Financing Receivable, Modifications, Number of Contracts Outstanding Principal Balance Financing Receivable, Modifications, Post-Modification Recorded Investment Initial advance at the time of modification Loans and Leases Receivable, Impaired, Initial Loan DIsbursement Loans and Leases Receivable, Impaired by Modification, Initial Loan Disbursement on construction-type loans. Other Real Estate Owned Real Estate Owned [Text Block] Investment Holdings [Table] Investment Holdings [Table] Investment Holdings [Line Items] Investment Holdings [Line Items] Fair Value Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value [Abstract] Less than 12 Months Debt Securities, Available-For-Sale, Continuous Unrealized Loss Position, Less Than 12 Months Debt Securities, Available-For-Sale, Continuous Unrealized Loss Position, Less Than 12 Months 12 Months or Longer Debt Securities, Available-For-Sale, Continuous Unrealized Loss Position. 12 Months Or Longer Debt Securities, Available-For-Sale, Continuous Unrealized Loss Position. 12 Months Or Longer Total Debt Securities, Available-For-Sale, Unrealized Loss Position Debt Securities, Available-For-Sale, Unrealized Loss Position Unrealized Losses Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Loss [Abstract] Less than 12 Months Debt Securities, Available-For-Sale, Continuous Unrealized Loss Position, Less Than 12 Months, Accumulated Loss Debt Securities, Available-For-Sale, Continuous Unrealized Loss Position, Less Than 12 Months, Accumulated Loss 12 Months or Longer Debt Securities, Available-For-Sale, Continuous Unrealized Loss Position, 12 Months Or Longer, Accumulated Loss Debt Securities, Available-For-Sale, Continuous Unrealized Loss Position, 12 Months Or Longer, Accumulated Loss Total