Summary of Significant Accounting Policies - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2022 USD ($) trust office segment county	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)
Significant Of Accounting Policies [Line Items]
Number of subsidiary business trusts (in trusts) | trust	5
Number of loan production offices (in offices) | office	2
Company's investments in the trusts	$ 1,757,000
Number of business segments (in segments) | segment	1
Net unrealized gains (losses)	$ 35,000	$ (718,000)
Accrued interest write off	0	0	$ 0
Credit losses recognized	0	0	0
Credit loss	$ 0	$ 0	$ 0
Minimum
Significant Of Accounting Policies [Line Items]
Loans held-for-sale, term	5 years
Regulatory liability, amortization period	15 years
Maximum
Significant Of Accounting Policies [Line Items]
Loans held-for-sale, term	10 years
Regulatory liability, amortization period	30 years
Furniture and equipment | Minimum
Significant Of Accounting Policies [Line Items]
Estimated useful lives of the related assets or lease terms	3 years
Furniture and equipment | Maximum
Significant Of Accounting Policies [Line Items]
Estimated useful lives of the related assets or lease terms	10 years
Land improvements and buildings | Minimum
Significant Of Accounting Policies [Line Items]
Estimated useful lives of the related assets or lease terms	15 years
Land improvements and buildings | Maximum
Significant Of Accounting Policies [Line Items]
Estimated useful lives of the related assets or lease terms	40 years
North Valley Bancorp
Significant Of Accounting Policies [Line Items]
Number of subsidiary business trusts (in trusts) | trust	3
California
Significant Of Accounting Policies [Line Items]
Number of counties (in counties) | county	32