Regulatory Matters - Actual and Required Capital Ratios of Bank (Detail) $ in Thousands	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)
Parent
Schedule of Capitalization [Line Items]
Total Capital (to Risk Weighted Assets), Actual, Amount	$ 893,294	$ 793,433
Tier 1 Capital (to Risk Weighted Assets), Actual, Amount	820,654	727,879
Common Equity Tier 1 Capital (to Risk Weighted Assets), Actual, Amount	764,319	671,975
Tier 1 Capital (to Average Assets), Actual, Amount	$ 820,654	$ 727,879
Total Capital (to Risk Weighted Assets), Actual, Ratio	0.1542	0.1522
Tier 1 Capital (to Risk Weighted Assets), Actual, Ratio	0.1417	0.1396
Common Equity Tier 1 Capital (to Risk Weighted Assets), Actual, Ratio	0.1319	0.1289
Tier 1 Capital (to Average Assets), Actual, Ratio	0.0988	0.0993
Parent \| Required for Capital Adequacy Purposes
Schedule of Capitalization [Line Items]
Total Capital (to Risk Weighted Assets), Minimum Capital Requirement, Amount	$ 608,258	$ 547,352
Tier 1 Capital (to Risk Weighted Assets), Minimum Capital Requirement, Amount	492,399	443,094
Common Equity Tier 1 Capital (to Risk Weighted Assets), Minimum Capital Requirement, Amount	405,505	364,901
Tier 1 Capital (to Average Assets), Minimum Capital Requirement, Amount	$ 332,205	$ 293,138
Total Capital (to Risk Weighted Assets), Minimum Capital Requirement, Ratio	0.1050	0.1050
Tier 1 Capital (to Risk Weighted Assets), Minimum Capital Requirement, Ratio	0.0850	0.0850
Common Equity Tier 1 Capital (to Risk Weighted Assets), Minimum Capital Requirement, Ratio	7.00%	7.00%
Tier 1 Capital (to Average Assets), Minimum Capital Requirement, Ratio	0.0400	0.0400
Tri Counties Bank
Schedule of Capitalization [Line Items]
Total Capital (to Risk Weighted Assets), Actual, Amount	$ 884,255	$ 780,320
Tier 1 Capital (to Risk Weighted Assets), Actual, Amount	811,713	714,811
Common Equity Tier 1 Capital (to Risk Weighted Assets), Actual, Amount	811,713	714,811
Tier 1 Capital (to Average Assets), Actual, Amount	$ 811,713	$ 714,811
Total Capital (to Risk Weighted Assets), Actual, Ratio	0.1528	0.1497
Tier 1 Capital (to Risk Weighted Assets), Actual, Ratio	0.1403	0.1372
Common Equity Tier 1 Capital (to Risk Weighted Assets), Actual, Ratio	0.1403	0.1372
Tier 1 Capital (to Average Assets), Actual, Ratio	0.0977	0.0976
Total Capital (to Risk Weighted Assets), Minimum To Be Well Capitalized Under Prompt Corrective Action Provisions, Amount	$ 578,676	$ 521,101
Tier 1 Capital (to Risk Weighted Assets), Minimum To Be Well Capitalized Under Prompt Corrective Action Provisions, Amount	462,941	416,881
Common Equity Tier 1 Capital (to Risk Weighted Assets), Minimum To Be Well Capitalized Under Prompt Corrective Action Provisions, Amount	376,140	338,716
Tier 1 Capital (to Average Assets), Minimum To Be Well Capitalized Under Prompt Corrective Action Provisions, Amount	$ 415,245	$ 366,186
Total Capital (to Risk Weighted Assets), Minimum To Be Well Capitalized Under Prompt Corrective Action Provisions, Ratio	0.1000	0.1000
Tier 1 Capital (to Risk Weighted Assets), Minimum To Be Well Capitalized Under Prompt Corrective Action Provisions, Ratio	0.0800	0.0800
Common Equity Tier 1 Capital (to Risk Weighted Assets), Minimum To Be Well Capitalized Under Prompt Corrective Action Provisions, Ratio	6.50%	6.50%
Tier 1 Capital (to Average Assets), Minimum To Be Well Capitalized Under Prompt Corrective Action Provisions, Ratio	0.0500	0.0500
Tri Counties Bank \| Required for Capital Adequacy Purposes
Schedule of Capitalization [Line Items]
Total Capital (to Risk Weighted Assets), Minimum Capital Requirement, Amount	$ 607,610	$ 547,156
Tier 1 Capital (to Risk Weighted Assets), Minimum Capital Requirement, Amount	491,875	442,936
Common Equity Tier 1 Capital (to Risk Weighted Assets), Minimum Capital Requirement, Amount	405,073	364,771
Tier 1 Capital (to Average Assets), Minimum Capital Requirement, Amount	$ 332,196	$ 292,949
Total Capital (to Risk Weighted Assets), Minimum Capital Requirement, Ratio	0.1050	0.1050
Tier 1 Capital (to Risk Weighted Assets), Minimum Capital Requirement, Ratio	0.0850	0.0850
Common Equity Tier 1 Capital (to Risk Weighted Assets), Minimum Capital Requirement, Ratio	7.00%	7.00%
Tier 1 Capital (to Average Assets), Minimum Capital Requirement, Ratio	0.0400	0.0400

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