Loans and Credit Quality - Narrative (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2019 USD ($) segment	Dec. 31, 2018 USD ($)	Mar. 31, 2018 USD ($)
Financing Receivable, Impaired [Line Items]
Number of portfolio segments | segment	2
Concentration percentage	10.00%	10.00%
Allowance for unfunded commitments	$ 1,360	$ 1,400	$ 1,400
Washington | Residential Mortgage And Multifamily [Member]
Financing Receivable, Impaired [Line Items]
Percentage of loan portfolio	12.50%	13.10%
California | Residential Mortgage And Multifamily [Member]
Financing Receivable, Impaired [Line Items]
Percentage of loan portfolio	10.20%	10.20%
Federal Home Loan Bank Advances [Member]
Financing Receivable, Impaired [Line Items]
Loans pledged as collateral	$ 1,930,000	$ 2,160,000
Federal Reserve Bank Advances [Member]
Financing Receivable, Impaired [Line Items]
Loans pledged as collateral	$ 449,600	$ 502,700