Regulatory Matters - Actual and Required Capital Ratios of Bank (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Parent
Schedule of Capitalization [Line Items]
Total Capital (to Risk Weighted Assets), Actual, Amount	$ 753,200	$ 682,419
Tier 1 Capital (to Risk Weighted Assets), Actual, Amount	719,809	647,262
Common Equity Tier 1 Capital (to Risk Weighted Assets), Actual, Amount	664,296	591,933
Tier 1 Capital (to Average Assets), Actual, Amount	$ 719,809	$ 647,262
Total Capital (to Risk Weighted Assets), Actual, Ratio	15.07%	14.40%
Tier 1 Capital (to Risk Weighted Assets), Actual, Ratio	14.40%	13.66%
Common Equity Tier 1 Capital (to Risk Weighted Assets), Actual, Ratio	13.29%	12.49%
Tier 1 Capital (to Average Assets), Actual, Ratio	11.55%	10.68%
Parent \| Required for Capital Adequacy Purposes
Schedule of Capitalization [Line Items]
Total Capital (to Risk Weighted Assets), Minimum Capital Requirement, Amount	$ 524,944	$ 497,486
Tier 1 Capital (to Risk Weighted Assets), Minimum Capital Requirement, Amount	424,955	402,727
Common Equity Tier 1 Capital (to Risk Weighted Assets), Minimum Capital Requirement, Amount	349,963	331,658
Tier 1 Capital (to Average Assets), Minimum Capital Requirement, Amount	$ 249,343	$ 242,452
Total Capital (to Risk Weighted Assets), Minimum Capital Requirement, Ratio	10.50%	10.50%
Tier 1 Capital (to Risk Weighted Assets), Minimum Capital Requirement, Ratio	8.50%	8.50%
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	4.00%	4.00%
Tri Counties Bank
Schedule of Capitalization [Line Items]
Total Capital (to Risk Weighted Assets), Actual, Amount	$ 748,660	$ 680,624
Tier 1 Capital (to Risk Weighted Assets), Actual, Amount	715,269	645,467
Common Equity Tier 1 Capital (to Risk Weighted Assets), Actual, Amount	715,269	645,467
Tier 1 Capital (to Average Assets), Actual, Amount	$ 715,269	$ 645,467
Total Capital (to Risk Weighted Assets), Actual, Ratio	14.98%	14.37%
Tier 1 Capital (to Risk Weighted Assets), Actual, Ratio	14.31%	13.63%
Common Equity Tier 1 Capital (to Risk Weighted Assets), Actual, Ratio	14.31%	13.63%
Tier 1 Capital (to Average Assets), Actual, Ratio	11.47%	10.65%
Total Capital (to Risk Weighted Assets), Minimum To Be Well Capitalized Under Prompt Corrective Action Provisions, Amount	$ 499,770	$ 473,624
Tier 1 Capital (to Risk Weighted Assets), Minimum To Be Well Capitalized Under Prompt Corrective Action Provisions, Amount	399,816	378,899
Common Equity Tier 1 Capital (to Risk Weighted Assets), Minimum To Be Well Capitalized Under Prompt Corrective Action Provisions, Amount	324,851	307,856
Tier 1 Capital (to Average Assets), Minimum To Be Well Capitalized Under Prompt Corrective Action Provisions, Amount	$ 311,672	$ 303,059
Total Capital (to Risk Weighted Assets), Minimum To Be Well Capitalized Under Prompt Corrective Action Provisions, Ratio	10.00%	10.00%
Tier 1 Capital (to Risk Weighted Assets), Minimum To Be Well Capitalized Under Prompt Corrective Action Provisions, Ratio	8.00%	8.00%
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	5.00%	5.00%
Tri Counties Bank \| Required for Capital Adequacy Purposes
Schedule of Capitalization [Line Items]
Total Capital (to Risk Weighted Assets), Minimum Capital Requirement, Amount	$ 524,759	$ 497,305
Tier 1 Capital (to Risk Weighted Assets), Minimum Capital Requirement, Amount	424,805	402,581
Common Equity Tier 1 Capital (to Risk Weighted Assets), Minimum Capital Requirement, Amount	349,839	331,537
Tier 1 Capital (to Average Assets), Minimum Capital Requirement, Amount	$ 249,337	$ 242,447
Total Capital (to Risk Weighted Assets), Minimum Capital Requirement, Ratio	10.50%	10.50%
Tier 1 Capital (to Risk Weighted Assets), Minimum Capital Requirement, Ratio	8.50%	8.50%
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	4.00%	4.00%

Common Equity Tier One Risk Based Capital Required For Capital Adequacy To Risk Weighted Assets

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Common Equity Tier One Risk Based Capital Required to be Well Capitalized to Risk Weighted Assets

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The amount of total capital as defined in the regulations.

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The amount of Total Capital required to be categorized as well as capitalized under the regulatory framework for prompt corrective action.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Tier 1 Leverage Capital as defined in the regulations. Also called Core Capital.

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