Summary of Significant Accounting Policies - Additional Information (Detail) $ in Millions	9 Months Ended
	Sep. 30, 2023 USD ($) trust office county segment
Significant Accounting Policies [Line Items]
Number of subsidiary business trusts (in trusts)	5
Number of subsidiary business trusts organized by the company (in trusts)	2
Company's investments in the trusts | $	$ 1.8
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) | office	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