Shareholders' Equity, Compliance with Regulatory Capital Requirements (Details) $ in Thousands	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)
CET1 capital to risk-weighted assets [Abstract]
Actual Amount	$ 493,438	$ 450,687
Required for Capital Adequacy Purposes, Amount	$ 191,984	$ 173,674
CET1 capital to risk-weighted assets, Ratio [Abstract]
Actual Ratio	0.1157	0.1168
Required for Capital Adequacy Purposes, Ratio	0.045	0.045
Tier 1 capital to risk-weighted assets [Abstract]
Actual Amount	$ 503,438	$ 460,687
Minimum Capital Requirement, Amount	$ 255,978	$ 231,566
Tier 1 capital to risk-weighted assets, Ratio [Abstract]
Actual Ratio	0.118	0.1194
Minimum Capital Requirement, Ratio	0.06	0.06
Risk-based capital to risk-weighted assets [Abstract]
Actual Amount	$ 556,964	$ 509,091
Minimum Capital Requirement, Amount	$ 341,305	$ 308,755
Risk-based capital to risk-weighted assets, Ratio [Abstract]
Actual Ratio	0.1306	0.1319
Minimum Capital Requirement, Ratio	0.08	0.08
Tier 1 leverage capital ratio [Abstract]
Actual Amount	$ 503,438	$ 460,687
Minimum Capital Requirement, Amount	$ 215,201	$ 206,606
Tier 1 leverage capital ratio, Ratio [Abstract]
Actual Ratio	0.0936	0.0892
Minimum Capital Requirement, Ratio	0.04	0.04
Farmers & Merchants Bank [Member]
CET1 capital to risk-weighted assets [Abstract]
Actual Amount	$ 502,838	$ 459,813
Required for Capital Adequacy Purposes, Amount	191,970	173,664
Minimum to be Categorized as "Well Capitalized" Under Prompt Corrective Action Regulation, Amount	$ 277,290	$ 250,847
CET1 capital to risk-weighted assets, Ratio [Abstract]
Actual Ratio	0.1179	0.1191
Required for Capital Adequacy Purposes, Ratio	0.045	0.045
Minimum to be Categorized as "Well Capitalized" Under Prompt Corrective Action Regulation, Ratio	0.065	0.065
Tier 1 capital to risk-weighted assets [Abstract]
Actual Amount	$ 502,838	$ 459,813
Minimum Capital Requirement, Amount	255,960	231,551
Well Capitalized Requirement, Amount	$ 341,280	$ 308,735
Tier 1 capital to risk-weighted assets, Ratio [Abstract]
Actual Ratio	0.1179	0.1191
Minimum Capital Requirement, Ratio	0.06	0.06
Well Capitalized Requirement, Ratio	0.08	0.08
Risk-based capital to risk-weighted assets [Abstract]
Actual Amount	$ 556,361	$ 508,215
Minimum Capital Requirement, Amount	341,280	308,735
Well Capitalized Requirement, Amount	$ 426,600	$ 385,919
Risk-based capital to risk-weighted assets, Ratio [Abstract]
Actual Ratio	0.1304	0.1317
Minimum Capital Requirement, Ratio	0.08	0.08
Well Capitalized Requirement, Ratio	0.10	0.10
Tier 1 leverage capital ratio [Abstract]
Actual Amount	$ 502,838	$ 459,813
Minimum Capital Requirement, Amount	215,018	206,426
Well Capitalized Requirement, Amount	$ 268,772	$ 258,033
Tier 1 leverage capital ratio, Ratio [Abstract]
Actual Ratio	0.0935	0.0891
Minimum Capital Requirement, Ratio	0.04	0.04
Well Capitalized Requirement, Ratio	0.05	0.05

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 505
-Section 50
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-URI https://asc.fasb.org/extlink&oid=117337116&loc=SL5958570-112826

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