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Acquisition - Narrative (Details)			12 Months Ended
	Nov. 21, 2017 USD ($) branch	Nov. 29, 2013 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Business Acquisition [Line Items]
Goodwill			$ 30,140,000	$ 30,140,000
Amortization of core deposit intangible			921,000	529,000
Bank of Napa, N.A. (Napa)
Business Acquisition [Line Items]
Number of branch offices | branch	2
Loans acquired	$ 134,700,000
Deposits assumed	249,900,000
Investment securities acquired	$ 75,500,000
Shares received by Napa shareholders in merger per acquiree share	0.307
Goodwill	$ 23,700,000
Goodwill impairment			0	0
NorCal Community Bancorp
Business Acquisition [Line Items]
Goodwill		$ 6,400,000
Core deposit intangible
Business Acquisition [Line Items]
Core deposit intangible asset			$ 5,571,000
Useful life of core deposit intangible asset			10 years
Core deposit intangible | Bank of Napa, N.A. (Napa)
Business Acquisition [Line Items]
Core deposit intangible asset	$ 4,400,000
Amortization of core deposit intangible			$ 508,000	$ 56,000
Useful life of core deposit intangible asset	10 years
Core deposit intangible | NorCal Community Bancorp
Business Acquisition [Line Items]
Core deposit intangible asset		$ 4,600,000
Useful life of core deposit intangible asset		10 years

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Business Combination, Consideration Transferred, Equity Interests Issued and Issuable, Entity Shares Issued Per Acquiree Share, Ratio

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Amount of investments in debt and equity securities, including, but not limited to, held-to-maturity, trading and available-for-sale expected to be converted to cash, sold or exchanged within one year or the normal operating cycle, if longer, acquired at the acquisition date.

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Useful life of finite-lived intangible assets, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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