Loans and Allowance for Credit Losses on Loans - Outstanding and Aging Analysis (Details)	3 Months Ended
	Mar. 31, 2022 USD ($) branch	Mar. 31, 2021 USD ($)	Dec. 31, 2021 USD ($) loan	Aug. 06, 2021 USD ($)	Jun. 30, 2021 USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans at amortized cost	$ 2,201,854,000		$ 2,255,645,000
Loans past due more than 90 days still accruing	0
Financing receivable, nonaccrual, earning interest on cash basis	0		0
Financing receivable, nonaccrual, interest income	$ 0	$ 0
Financing receivable, number of loans placed on nonaccrual status \| branch	1
Financing receivable, nonaccrual, amortized cost	$ 16,000	$ 0
Financing receivable, accrued interest, writeoff	1,000
Commercial loans \| Commercial and industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans at amortized cost	248,625,000		301,602,000
Loans past due more than 90 days still accruing			229,000
Commercial loans \| Commercial and industrial \| SBA PPP
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans at amortized cost	40,600,000		$ 111,200,000		$ 444,100,000
Number of loans \| loan			2
Commercial loans \| Commercial and industrial \| American River Bank (ARB) \| SBA PPP
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans at amortized cost				$ 18,600,000
Commercial real estate loans \| Commercial owner-occupied
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans at amortized cost	391,924,000		$ 392,345,000
Commercial real estate loans \| Commercial investor-owned
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans at amortized cost	1,176,918,000		1,189,021,000
Commercial real estate loans \| Construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans at amortized cost	131,015,000		119,840,000
Residential loans \| Home equity
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans at amortized cost	88,092,000		88,746,000
Residential loans \| Other residential
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans at amortized cost	114,277,000		114,558,000
Consumer loans \| Installment and other consumer loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans at amortized cost	51,003,000		49,533,000
Financial asset, other than financial asset acquired with credit deterioration
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans at amortized cost	2,201,854,000		2,255,645,000
Non-accrual	7,678,000		8,376,000
Non-accrual loans with no allowance	7,678,000		8,376,000
Financial asset, other than financial asset acquired with credit deterioration \| Total past due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans at amortized cost	2,643,000		2,314,000
Financial asset, other than financial asset acquired with credit deterioration \| 30-59 days past due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans at amortized cost	2,130,000		1,536,000
Financial asset, other than financial asset acquired with credit deterioration \| 60-89 days past due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans at amortized cost	443,000		461,000
Financial asset, other than financial asset acquired with credit deterioration \| 90 days or more past due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans at amortized cost	70,000		317,000
Financial asset, other than financial asset acquired with credit deterioration \| Current
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans at amortized cost	2,199,211,000		2,253,331,000
Financial asset, other than financial asset acquired with credit deterioration \| Commercial loans \| Commercial and industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans at amortized cost	248,625,000		301,602,000
Non-accrual	0		0
Non-accrual loans with no allowance	0		0
Financial asset, other than financial asset acquired with credit deterioration \| Commercial loans \| Commercial and industrial \| Total past due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans at amortized cost	776,000		625,000
Financial asset, other than financial asset acquired with credit deterioration \| Commercial loans \| Commercial and industrial \| 30-59 days past due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans at amortized cost	435,000		2,000
Financial asset, other than financial asset acquired with credit deterioration \| Commercial loans \| Commercial and industrial \| 60-89 days past due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans at amortized cost	341,000		394,000
Financial asset, other than financial asset acquired with credit deterioration \| Commercial loans \| Commercial and industrial \| 90 days or more past due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans at amortized cost	0		229,000
Financial asset, other than financial asset acquired with credit deterioration \| Commercial loans \| Commercial and industrial \| Current
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans at amortized cost	247,849,000		300,977,000
Financial asset, other than financial asset acquired with credit deterioration \| Commercial real estate loans \| Commercial owner-occupied
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans at amortized cost	391,924,000		392,345,000
Non-accrual	7,272,000		7,269,000
Non-accrual loans with no allowance	7,272,000		7,269,000
Financial asset, other than financial asset acquired with credit deterioration \| Commercial real estate loans \| Commercial owner-occupied \| Total past due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans at amortized cost	324,000		0
Financial asset, other than financial asset acquired with credit deterioration \| Commercial real estate loans \| Commercial owner-occupied \| 30-59 days past due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans at amortized cost	324,000		0
Financial asset, other than financial asset acquired with credit deterioration \| Commercial real estate loans \| Commercial owner-occupied \| 60-89 days past due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans at amortized cost	0		0
Financial asset, other than financial asset acquired with credit deterioration \| Commercial real estate loans \| Commercial owner-occupied \| 90 days or more past due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans at amortized cost	0		0
Financial asset, other than financial asset acquired with credit deterioration \| Commercial real estate loans \| Commercial owner-occupied \| Current
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans at amortized cost	391,600,000		392,345,000
Financial asset, other than financial asset acquired with credit deterioration \| Commercial real estate loans \| Commercial investor-owned
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans at amortized cost	1,176,918,000		1,189,021,000
Non-accrual	0		694,000
Non-accrual loans with no allowance	0		694,000
Financial asset, other than financial asset acquired with credit deterioration \| Commercial real estate loans \| Commercial investor-owned \| Total past due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans at amortized cost	0		0
Financial asset, other than financial asset acquired with credit deterioration \| Commercial real estate loans \| Commercial investor-owned \| 30-59 days past due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans at amortized cost	0		0
Financial asset, other than financial asset acquired with credit deterioration \| Commercial real estate loans \| Commercial investor-owned \| 60-89 days past due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans at amortized cost	0		0
Financial asset, other than financial asset acquired with credit deterioration \| Commercial real estate loans \| Commercial investor-owned \| 90 days or more past due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans at amortized cost			0
Financial asset, other than financial asset acquired with credit deterioration \| Commercial real estate loans \| Commercial investor-owned \| Current
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans at amortized cost	1,176,918,000		1,189,021,000
Financial asset, other than financial asset acquired with credit deterioration \| Commercial real estate loans \| Construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans at amortized cost	131,015,000		119,840,000
Non-accrual	0		0
Non-accrual loans with no allowance	0		0
Financial asset, other than financial asset acquired with credit deterioration \| Commercial real estate loans \| Construction \| Total past due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans at amortized cost	0		0
Financial asset, other than financial asset acquired with credit deterioration \| Commercial real estate loans \| Construction \| 30-59 days past due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans at amortized cost	0		0
Financial asset, other than financial asset acquired with credit deterioration \| Commercial real estate loans \| Construction \| 60-89 days past due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans at amortized cost	0		0
Financial asset, other than financial asset acquired with credit deterioration \| Commercial real estate loans \| Construction \| 90 days or more past due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans at amortized cost	0		0
Financial asset, other than financial asset acquired with credit deterioration \| Commercial real estate loans \| Construction \| Current
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans at amortized cost	131,015,000		119,840,000
Financial asset, other than financial asset acquired with credit deterioration \| Residential loans \| Home equity
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans at amortized cost	88,092,000		88,746,000
Non-accrual	390,000		413,000
Non-accrual loans with no allowance	390,000		413,000
Financial asset, other than financial asset acquired with credit deterioration \| Residential loans \| Home equity \| Total past due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans at amortized cost	553,000		653,000
Financial asset, other than financial asset acquired with credit deterioration \| Residential loans \| Home equity \| 30-59 days past due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans at amortized cost	399,000		498,000
Financial asset, other than financial asset acquired with credit deterioration \| Residential loans \| Home equity \| 60-89 days past due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans at amortized cost	100,000		67,000
Financial asset, other than financial asset acquired with credit deterioration \| Residential loans \| Home equity \| 90 days or more past due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans at amortized cost	54,000		88,000
Financial asset, other than financial asset acquired with credit deterioration \| Residential loans \| Home equity \| Current
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans at amortized cost	87,539,000		88,093,000
Financial asset, other than financial asset acquired with credit deterioration \| Residential loans \| Other residential
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans at amortized cost	114,277,000		114,558,000
Non-accrual	0		0
Non-accrual loans with no allowance	0		0
Financial asset, other than financial asset acquired with credit deterioration \| Residential loans \| Other residential \| Total past due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans at amortized cost	635,000		0
Financial asset, other than financial asset acquired with credit deterioration \| Residential loans \| Other residential \| 30-59 days past due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans at amortized cost	635,000		0
Financial asset, other than financial asset acquired with credit deterioration \| Residential loans \| Other residential \| 60-89 days past due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans at amortized cost	0		0
Financial asset, other than financial asset acquired with credit deterioration \| Residential loans \| Other residential \| 90 days or more past due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans at amortized cost	0		0
Financial asset, other than financial asset acquired with credit deterioration \| Residential loans \| Other residential \| Current
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans at amortized cost	113,642,000		114,558,000
Financial asset, other than financial asset acquired with credit deterioration \| Consumer loans \| Installment and other consumer loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans at amortized cost	51,003,000		49,533,000
Non-accrual	16,000		0
Non-accrual loans with no allowance	16,000		0
Financial asset, other than financial asset acquired with credit deterioration \| Consumer loans \| Installment and other consumer loans \| Total past due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans at amortized cost	355,000		1,036,000
Financial asset, other than financial asset acquired with credit deterioration \| Consumer loans \| Installment and other consumer loans \| 30-59 days past due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans at amortized cost	337,000		1,036,000
Financial asset, other than financial asset acquired with credit deterioration \| Consumer loans \| Installment and other consumer loans \| 60-89 days past due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans at amortized cost	2,000		0
Financial asset, other than financial asset acquired with credit deterioration \| Consumer loans \| Installment and other consumer loans \| 90 days or more past due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans at amortized cost	16,000		0
Financial asset, other than financial asset acquired with credit deterioration \| Consumer loans \| Installment and other consumer loans \| Current
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans at amortized cost	$ 50,648,000		$ 48,497,000