Summary of Significant Accounting Policies (Details)	12 Months Ended
	Dec. 31, 2019 USD ($) location	Jan. 01, 2020 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Accounting Policies [Line Items]
Number Of Branch Locations | location	146
FHLB membership stock purchase requirement cap	$ 10,000,000
Federal Home Loan Bank stock, par value	100
Loans and Leases Receivable, Nonaccrual Loans Considered Impaired	500,000
Loans and Leases Receivable, Loans Evaluated For Impairment On Quarterly Basis, Outstanding	$ 500,000
Number Of Days Used To Determine Treatment As Cash Equivalent	90 days
Number of Days of Delinquency at Which Loans Are Categorized As Non Accrual Status	90 days
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	71
OREGON
Accounting Policies [Line Items]
Number Of Branch Locations | location	61
IDAHO
Accounting Policies [Line Items]
Number Of Branch Locations | location	14
Vehicles [Member]
Accounting Policies [Line Items]
Property, Plant and Equipment, Estimated Useful Lives	P5Y
Minimum [Member] | Building and Building Improvements [Member]
Accounting Policies [Line Items]
Property, Plant and Equipment, Estimated Useful Lives	P5Y
Minimum [Member] | Furniture and Fixtures [Member]
Accounting Policies [Line Items]
Property, Plant and Equipment, Estimated Useful Lives	P3Y
Minimum [Member] | Software [Member]
Accounting Policies [Line Items]
Property, Plant and Equipment, Estimated Useful Lives	P3Y
Maximum [Member] | Building and Building Improvements [Member]
Accounting Policies [Line Items]
Property, Plant and Equipment, Estimated Useful Lives	P39Y
Maximum [Member] | Furniture and Fixtures [Member]
Accounting Policies [Line Items]
Property, Plant and Equipment, Estimated Useful Lives	P7Y
Maximum [Member] | Software [Member]
Accounting Policies [Line Items]
Property, Plant and Equipment, Estimated Useful Lives	P5Y
Accounting Standards Update 2016-02 [Member]
Accounting Policies [Line Items]
Change in other assets due to adoption of new ASU	$ 49,200,000
Change in other liabilities due to adoption of new ASU	48,200,000
Cumulative Effect of New Accounting Principle in Period of Adoption			$ (782,000)
Accounting Standards Update 2016-02 [Member] | Retained Earnings [Member]
Accounting Policies [Line Items]
Cumulative Effect of New Accounting Principle in Period of Adoption			$ (782,000)
Accounting Standards Update 2018-02 [Member]
Accounting Policies [Line Items]
Cumulative Effect of New Accounting Principle in Period of Adoption					$ 0
Accounting Standards Update 2018-02 [Member] | Retained Earnings [Member]
Accounting Policies [Line Items]
Cumulative Effect of New Accounting Principle in Period of Adoption					(4,082,000)
Accounting Standards Update 2016-09 [Member]
Accounting Policies [Line Items]
Cumulative Effect of New Accounting Principle in Period of Adoption					(67,000)
Accounting Standards Update 2016-09 [Member] | Retained Earnings [Member]
Accounting Policies [Line Items]
Cumulative Effect of New Accounting Principle in Period of Adoption					117,000
Accounting Standards Update 2016-09 [Member] | Common Stock [Member]
Accounting Policies [Line Items]
Cumulative Effect of New Accounting Principle in Period of Adoption					$ (184,000)
Accounting Standards Update 2016-01 [Member]
Accounting Policies [Line Items]
Cumulative Effect of New Accounting Principle in Period of Adoption				$ 0
Accounting Standards Update 2016-01 [Member] | Retained Earnings [Member]
Accounting Policies [Line Items]
Cumulative Effect of New Accounting Principle in Period of Adoption				$ 157,000
Accounting Standards Update 2018-15 [Member]
Accounting Policies [Line Items]
Change in other assets due to adoption of new ASU	1,500,000
Accounting Standards Update 2016-13 [Member]
Accounting Policies [Line Items]
Change in allowance for credit loss due to adoption of new ASU		$ 1,600,000
Change in allowance for unfunded commitments and letters of credit due to adoption of new ASU		$ 1,600,000
Accounting Standards Update 2016-13 [Member] | Retained Earnings [Member]
Accounting Policies [Line Items]
Cumulative Effect of New Accounting Principle in Period of Adoption	2,500,000
Designated as Hedging Instrument [Member] | Interest rate collar [Domain]
Accounting Policies [Line Items]
Derivative, Notional Amount	$ 500,000,000.0