Loans and Credit Quality - Narrative (Details)	12 Months Ended
Dec. 31, 2018 USD ($) segment	Dec. 31, 2017 USD ($)
Financing Receivable, Impaired [Line Items]
Number of operating segments \| segment	2
Total loans receivable before fees and costs	$ 5,093,747,000	$ 4,529,627,000
Total loans held for investment	$ 5,093,747,000	4,529,627,000
Number of days past due on re-default consumer loans	60 days
Number of days past due on re-default commercial loans	90 days
Federal Home Loan Bank Advances [Member]
Financing Receivable, Impaired [Line Items]
Loans pledged as collateral	$ 2,160,000,000	1,810,000,000
Federal Reserve Bank Advances [Member]
Financing Receivable, Impaired [Line Items]
Loans pledged as collateral	$ 502,700,000	$ 663,800,000
WASHINGTON \| Residential Mortgage And Multifamily [Member]
Financing Receivable, Impaired [Line Items]
Percentage of loan portfolio	13.10%
WASHINGTON \| Residential Mortgage [Member]
Financing Receivable, Impaired [Line Items]
Percentage of loan portfolio		15.00%
CALIFORNIA \| Residential Mortgage And Multifamily [Member]
Financing Receivable, Impaired [Line Items]
Percentage of loan portfolio	10.20%
CALIFORNIA \| Residential Mortgage [Member]
Financing Receivable, Impaired [Line Items]
Percentage of loan portfolio		10.90%
Doubtful [Member]
Financing Receivable, Impaired [Line Items]
Total loans receivable before fees and costs	$ 0	$ 0
Unlikely to be Collected Financing Receivable [Member]
Financing Receivable, Impaired [Line Items]
Total loans receivable before fees and costs	$ 0	$ 0

Percentage of total loan portfolio.

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Trouble Debt Restructuring, Re-Default, Number Of Days Past Due, Commercial

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Trouble Debt Restructuring, Re-Default, Number of Days Past Due, Consumer

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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- Definition

Amount, before allowance and fees, of loans and leases receivable. Excludes loans and leases covered under loss sharing agreements.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=82891408&loc=d3e4428-111522

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Amount before allowance of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Includes deferred interest and fees, undisbursed portion of loan balance, unamortized costs and premiums and discounts from face amounts. Excludes loans and leases covered under loss sharing agreements.

+ References

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Carrying amount as of the balance sheet date of loans that have been pledged as collateral for borrowings. If the secured party has the right by contract or custom to sell or re-pledge the collateral, then the debtor reclassifies that asset and report that asset in its statement of financial position separately from other assets not so encumbered.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 30
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=66007379&loc=d3e113888-111728

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Number of operating segments. An operating segment is a component of an enterprise: (a) that engages in business activities from which it may earn revenues and incur expenses (including revenues and expenses relating to transactions with other components of the same enterprise), (b) whose operating results are regularly reviewed by the enterprise's chief operating decision maker to make decisions about resources to be allocated to the segment and assess its performance, and (c) for which discrete financial information is available. An operating segment may engage in business activities for which it has yet to earn revenues, for example, start-up operations may be operating segments before earning revenues.

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