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Concentrations of Credit Risk (Details) - USD ($) $ in Millions |  | 12 Months Ended
--- | --- | ---
Aug. 06, 2021 | Dec. 31, 2021 | Dec. 31, 2020
Small Business Administration Paycheck Protection Program | Commercial real estate |  |  |
Concentration Risk [Line Items] |  |  |
Decrease in unsecured loans |  | $ 180.4 |
Credit concentration risk | U.S. Government, its agencies and Government Sponsored Enterprises (GSEs) | U.S. Government And Government-Sponsored Enterprises |  |  |
Concentration Risk [Line Items] |  |  |
Concentration risk amount |  | $ 1,277.0 | $ 389.1
Concentration risk percentage |  | 85.00% | 78.00%
Credit concentration risk | U.S. Government, its agencies and Government Sponsored Enterprises (GSEs) | U.S. Government And Government-Sponsored Enterprises | American River Bank ARB |  |  |
Concentration Risk [Line Items] |  |  |
Concentration risk amount | $ 261.3 |  |
Credit concentration risk | Non-Government Sponsored Enterprises | U.S. Government And Government-Sponsored Enterprises |  |  |
Concentration Risk [Line Items] |  |  |
Concentration risk amount | $ 827.9 |  |
Credit concentration risk | Non-Government Sponsored Enterprises | Non-Government Sponsored Enterprises |  |  |
Concentration Risk [Line Items] |  |  |
Concentration risk percentage |  | 2.00% | 3.00%
Credit concentration risk | Loans portfolio |  |  |
Concentration Risk [Line Items] |  |  |
Concentration risk, threshold for major borrower, percentage |  | 3.00% |
Credit concentration risk | Loans on real estate | Residential loans |  |  |
Concentration Risk [Line Items] |  |  |
Concentration risk percentage |  | 84.00% | 76.00%

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