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Summary of Significant Accounting Policies - Additional Information (Detail) $ in Thousands	9 Months Ended
	Sep. 30, 2021 USD ($) office segment county trust
Significant Accounting Policies [Line Items]
Number of subsidiary business trusts (in trusts) | trust	5
Number of loan production offices (in offices)	2
Company's investments in the trusts | $	$ 1,741
Number of business segment (in segments) | segment	1
Loans contractual past due	90 days
North Valley Bancorp
Significant Accounting Policies [Line Items]
Number of loan production offices (in offices)	3
Minimum
Significant Accounting Policies [Line Items]
Loan term	5 years
Amortization period	15 years
Maximum
Significant Accounting Policies [Line Items]
Loan term	10 years
Amortization period	30 years
California
Significant Accounting Policies [Line Items]
Number of counties (in counties) | county	31

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Nonaccrual status loans contractual past due.

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Number Of Counties Bank Operates

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Number Of Loan Production Offices

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Number of subsidiary business trust.

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Significant Accounting Policies [Line Items]

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- Definition

This element represents the aggregate cost of investments accounted for under the equity method of accounting.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.12)
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- Definition

Period between issuance and maturity of loan held for sale, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
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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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Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 18
-URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e8672-108599

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Amortization period for the recovery of regulatory liability, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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