Regulatory Matters - Actual and Required Capital Ratios of Bank (Detail) $ in Thousands	Mar. 31, 2024 USD ($)	Dec. 31, 2023 USD ($)
Consolidated
Schedule of Capitalization [Line Items]
Total Capital (to Risk Weighted Assets)	$ 1,212,626	$ 1,196,106
Tier 1 Capital (to Risk Weighted Assets)	1,068,911	1,052,063
Common Equity Tier 1 Capital (to Risk Weighted Assets)	1,011,649	994,907
Tier 1 Capital (to Average Assets)	$ 1,068,911	$ 1,052,063
Total Capital Ratio (to Risk Weighted Assets)	0.1497	0.1473
Tier 1 Capital Ratio (to Risk Weighted Assets)	0.1320	0.1295
Common Equity Tier 1 Capital Ratio (to Risk Weighted Assets)	0.1249	0.1225
Tier 1 Capital Ratio (to Average Assets)	0.1101	0.1075
Consolidated \| Basel III Fully Phased In
Schedule of Capitalization [Line Items]
Total Capital (to Risk Weighted Assets), Minimum Capital Requirement	$ 850,469	$ 852,850
Tier 1 Capital (to Risk Weighted Assets), Minimum Capital Requirement	688,475	690,402
Common Equity Tier 1 Capital (to Risk Weighted Assets), Minimum Capital Requirement	566,979	568,566
Tier 1 Capital (to Average Assets), Minimum Capital Requirement	$ 388,326	$ 391,620
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)	$ 1,202,415	$ 1,190,542
Tier 1 Capital (to Risk Weighted Assets)	1,100,831	1,088,717
Common Equity Tier 1 Capital (to Risk Weighted Assets)	1,100,831	1,088,717
Tier 1 Capital (to Average Assets)	$ 1,100,831	$ 1,088,717
Total Capital Ratio (to Risk Weighted Assets)	0.1485	0.1466
Tier 1 Capital Ratio (to Risk Weighted Assets)	0.1359	0.1341
Common Equity Tier 1 Capital Ratio (to Risk Weighted Assets)	0.1359	0.1341
Tier 1 Capital Ratio (to Average Assets)	0.1134	0.1112
Total Capital (to Risk Weighted Assets), Minimum To Be Well Capitalized Under Prompt Corrective Action Provisions	$ 809,776	$ 812,046
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	$ 647,821	$ 649,637
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	$ 526,355	$ 527,830
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	$ 485,316	$ 489,468
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	$ 850,265	$ 852,648
Tier 1 Capital (to Risk Weighted Assets), Minimum Capital Requirement	688,310	690,239
Common Equity Tier 1 Capital (to Risk Weighted Assets), Minimum Capital Requirement	566,843	568,432
Tier 1 Capital (to Average Assets), Minimum Capital Requirement	$ 388,253	$ 391,574
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

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

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 942
-SubTopic 505
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (c)(1)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480696/942-505-50-1

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 942
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-Section 50
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