Regulatory Matters - Actual and Required Capital Ratios of Bank (Detail) $ in Thousands	Jun. 30, 2022 USD ($)	Dec. 31, 2021 USD ($)
Consolidated
Schedule of Capitalization [Line Items]
Total Capital (to Risk Weighted Assets)	$ 1,050,849	$ 893,294
Tier 1 Capital (to Risk Weighted Assets)	914,966	820,654
Common Equity Tier 1 Capital (to Risk Weighted Assets)	858,486	764,319
Tier 1 Capital (to Average Assets)	$ 914,966	$ 820,654
Total Capital Ratio (to Risk Weighted Assets)	0.1413	0.1542
Tier 1 Capital Ratio (to Risk Weighted Assets)	0.1230	0.1417
Common Equity Tier 1 Capital Ratio (to Risk Weighted Assets)	0.1154	0.1319
Tier 1 Capital Ratio (to Average Assets)	0.0935	0.0988
Consolidated \| Basel III Fully Phased In
Schedule of Capitalization [Line Items]
Total Capital (to Risk Weighted Assets), Minimum Capital Requirement	$ 781,114	$ 608,258
Tier 1 Capital (to Risk Weighted Assets), Minimum Capital Requirement	632,330	492,399
Common Equity Tier 1 Capital (to Risk Weighted Assets), Minimum Capital Requirement	520,743	405,505
Tier 1 Capital (to Average Assets), Minimum Capital Requirement	$ 391,612	$ 332,205
Total Capital Ratio (to Risk Weighted Assets), Minimum Capital Requirement	0.1050	0.1050
Tier 1 Capital Ratio (to Risk Weighted Assets), Minimum Capital Requirement	0.0850	0.0850
Common Equity Tier 1 Capital Ratio (to Risk Weighted Assets), Minimum Capital Requirement	7.00%	7.00%
Tier 1 Capital Ratio (to Average Assets), Minimum Capital Requirement	0.0400	0.0400
Tri Counties Bank
Schedule of Capitalization [Line Items]
Total Capital (to Risk Weighted Assets)	$ 1,044,231	$ 884,255
Tier 1 Capital (to Risk Weighted Assets)	951,178	811,713
Common Equity Tier 1 Capital (to Risk Weighted Assets)	951,178	811,713
Tier 1 Capital (to Average Assets)	$ 951,178	$ 811,713
Total Capital Ratio (to Risk Weighted Assets)	0.1404	0.1528
Tier 1 Capital Ratio (to Risk Weighted Assets)	0.1279	0.1403
Common Equity Tier 1 Capital Ratio (to Risk Weighted Assets)	0.1279	0.1403
Tier 1 Capital Ratio (to Average Assets)	0.0972	0.0977
Total Capital (to Risk Weighted Assets), Minimum To Be Well Capitalized Under Prompt Corrective Action Provisions	$ 743,526	$ 578,676
Capital Required to be Well Capitalized to Risk Weighted Assets	0.1000	0.1000
Tier 1 Capital (to Risk Weighted Assets), Minimum To Be Well Capitalized Under Prompt Corrective Action Provisions	$ 594,821	$ 462,941
Tier One Risk Based Capital Required to be Well Capitalized to Risk Weighted Assets	0.0800	0.0800
Common Equity Tier 1 Capital (to Risk Weighted Assets), Minimum To Be Well Capitalized Under Prompt Corrective Action Provisions	$ 483,292	$ 376,140
Common Equity Tier One Risk Based Capital Required to be Well Capitalized to Risk Weighted Assets	6.50%	6.50%
Tier 1 Capital (to Average Assets), Minimum To Be Well Capitalized Under Prompt Corrective Action Provisions	$ 489,052	$ 415,245
Tier One Leverage Capital Required to be Well Capitalized to Average Assets	0.0500	0.0500
Tri Counties Bank \| Basel III Fully Phased In
Schedule of Capitalization [Line Items]
Total Capital (to Risk Weighted Assets), Minimum Capital Requirement	$ 780,703	$ 607,610
Tier 1 Capital (to Risk Weighted Assets), Minimum Capital Requirement	631,997	491,875
Common Equity Tier 1 Capital (to Risk Weighted Assets), Minimum Capital Requirement	520,468	405,073
Tier 1 Capital (to Average Assets), Minimum Capital Requirement	$ 391,241	$ 332,196
Total Capital Ratio (to Risk Weighted Assets), Minimum Capital Requirement	0.1050	0.1050
Tier 1 Capital Ratio (to Risk Weighted Assets), Minimum Capital Requirement	0.0850	0.0850
Common Equity Tier 1 Capital Ratio (to Risk Weighted Assets), Minimum Capital Requirement	7.00%	7.00%
Tier 1 Capital Ratio (to Average Assets), Minimum Capital Requirement	0.0400	0.0400

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