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Summary of Significant Accounting Policies (Details) | 12 Months Ended |  |  |
--- | --- | --- | --- | ---
Dec. 31, 2020 USD ($) location | Jan. 01, 2020 USD ($) | Dec. 31, 2019 USD ($) | Dec. 31, 2018 USD ($)
Accounting Policies [Line Items] |  |  |  |
Number Of Branch Locations | location | 145 |  |  |
Number Of Days Used To Determine Treatment As Cash Equivalent | 90 |  |  |
FHLB membership stock purchase requirement cap | $ 10,000,000 |  |  |
Federal Home Loan Bank stock, par value | $ 100 |  |  |
Number of Days of Delinquency at Which Loans Are Categorized As Non Accrual Status | 90 |  |  |
Core Deposits [Member] |  |  |  |
Accounting Policies [Line Items] |  |  |  |
Estimated life of CDI, in years | 10 years |  |  |
WASHINGTON |  |  |  |
Accounting Policies [Line Items] |  |  |  |
Number Of Branch Locations | location | 70 |  |  |
OREGON |  |  |  |
Accounting Policies [Line Items] |  |  |  |
Number Of Branch Locations | location | 60 |  |  |
IDAHO |  |  |  |
Accounting Policies [Line Items] |  |  |  |
Number Of Branch Locations | location | 15 |  |  |
Vehicles [Member] |  |  |  |
Accounting Policies [Line Items] |  |  |  |
Property, Plant and Equipment, Estimated Useful Lives | 5 |  |  |
Minimum | Building and Building Improvements [Member] |  |  |  |
Accounting Policies [Line Items] |  |  |  |
Property, Plant and Equipment, Estimated Useful Lives | 5 |  |  |
Minimum | Furniture and Fixtures [Member] |  |  |  |
Accounting Policies [Line Items] |  |  |  |
Property, Plant and Equipment, Estimated Useful Lives | 3 |  |  |
Minimum | Software [Member] |  |  |  |
Accounting Policies [Line Items] |  |  |  |
Property, Plant and Equipment, Estimated Useful Lives | 3 |  |  |
Maximum | Building and Building Improvements [Member] |  |  |  |
Accounting Policies [Line Items] |  |  |  |
Property, Plant and Equipment, Estimated Useful Lives | 39 |  |  |
Maximum | Furniture and Fixtures [Member] |  |  |  |
Accounting Policies [Line Items] |  |  |  |
Property, Plant and Equipment, Estimated Useful Lives | 7 |  |  |
Maximum | Software [Member] |  |  |  |
Accounting Policies [Line Items] |  |  |  |
Property, Plant and Equipment, Estimated Useful Lives | 5 |  |  |
Accounting Standards Update 2016-13 |  |  |  |
Accounting Policies [Line Items] |  |  |  |
Change in allowance for credit loss due to adoption of new ASU |  | $ 1,632,000 |  |
Change in allowance for unfunded commitments and letters of credit due to adoption of new ASU |  | $ 1,570,000 | $ 0 | $ 0
Adjustment to opening retained earnings, net of tax, pursuant to adoption of ASU |  |  | 2,500,000 |
Accounting Standards Update 2016-13 | Retained Earnings |  |  |  |
Accounting Policies [Line Items] |  |  |  |
Adjustment to opening retained earnings, net of tax, pursuant to adoption of ASU |  |  | $ 2,457,000 |
Designated as Hedging Instrument | Interest rate collar |  |  |  |
Accounting Policies [Line Items] |  |  |  |
Derivative, Notional Amount | $ 500,000,000.0 |  |  |

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