Summary of Significant Accounting Policies (Details)	3 Months Ended	12 Months Ended
	Jun. 30, 2017 USD ($)	Dec. 31, 2017 USD ($) location $ / shares	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Accounting Policies [Line Items]
FHLB membership stock purchase requirement cap		$ 10,000,000
Gain on sale of merchant card services portfolio		$ 14,000,000	$ 0	$ 0
Number Of Branch Locations | location		155
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
Loans and Leases Receivable, Nonaccrual Loans Considered Impaired		$ 500,000
Loans and Leases Receivable, Loans Evaluated For Impairment On Quarterly Basis, Outstanding		500,000
Correction of immaterial error, pre-tax increase to interest income on taxable securities		1,800,000
Federal Home Loan Bank stock, par value		100
Correction of immaterial error, pre-tax increase to interest income on taxable securities - amount related to prior periods		$ 700,000
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		75
OREGON
Accounting Policies [Line Items]
Number Of Branch Locations | location		66
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 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
New Accounting Pronouncement or Change in Accounting Principle, Effect of Change on Net Income		$ 1,300,000
New Accounting Pronouncement or Change in Accounting Principle, Effect of Change on Diluted Earnings Per Share | $ / shares		$ 0.02
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]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Change on Net Income		$ 3,000	$ 33,000	$ 64,000
Merchant Card Services Agreement [Member]
Accounting Policies [Line Items]
Gain on sale of merchant card services portfolio		14,000,000
Net carrying amount of merchant card services portfolio upon sale	$ 0
Net revenue share - merchant card services		$ 1,100,000