Regulatory Matters (Detail) $ in Thousands	Jun. 30, 2026 USD ($)	Dec. 31, 2025 USD ($)
Consolidated
Schedule of Capitalization [Line Items]
Total capital (to risk weighted assets)	$ 1,283,711	$ 1,256,506
Tier 1 capital (to risk weighted assets)	1,176,231	1,151,744
Common equity Tier 1 capital (to risk weighted assets)	1,136,231	1,111,744
Tier 1 capital (to average assets)	$ 1,176,231	$ 1,151,744
Total capital ratio (to risk weighted assets)	0.1499	0.1505
Tier 1 capital ratio (to risk weighted assets)	0.1373	0.1379
Common equity Tier 1 capital ratio (to risk weighted assets)	0.1326	0.1331
Tier 1 capital ratio (to average assets)	0.1204	0.1184
Consolidated \| Basel III Fully Phased In
Schedule of Capitalization [Line Items]
Total capital (to risk weighted assets), minimum capital requirement	$ 899,458	$ 876,852
Tier 1 capital (to risk weighted assets), minimum capital requirement	728,132	709,832
Common equity Tier 1 capital (to risk weighted assets), minimum capital requirement	599,638	584,568
Tier 1 capital (to average assets), minimum capital requirement	$ 390,775	$ 389,131
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)	$ 1,279,898	$ 1,250,620
Tier 1 capital (to risk weighted assets)	1,172,450	1,145,890
Common equity Tier 1 capital (to risk weighted assets)	1,172,450	1,145,890
Tier 1 capital (to average assets)	$ 1,172,450	$ 1,145,890
Total capital ratio (to risk weighted assets)	0.1494	0.1498
Tier 1 capital ratio (to risk weighted assets)	0.1369	0.1372
Common equity Tier 1 capital ratio (to risk weighted assets)	0.1369	0.1372
Tier 1 capital ratio (to average assets)	0.1200	0.1178
Total capital (to risk weighted assets), minimum to be well capitalized under prompt corrective action provisions	$ 856,493	$ 834,960
Tier 1 capital (to risk weighted assets), minimum to be well capitalized under prompt corrective action provisions	685,194	667,968
Common equity Tier 1 capital (to risk weighted assets), minimum to be well capitalized under prompt corrective action provisions	556,720	542,724
Tier 1 capital (to average assets), minimum to be well capitalized under prompt corrective action provisions	$ 488,438	$ 486,227
Capital required to be well capitalized to risk weighted assets	0.1000	0.1000
Tier one risk based capital required to be well capitalized to risk weighted assets	0.0800	0.0800
Common equity tier one risk based capital required to be well capitalized to risk weighted assets	6.50%	6.50%
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	$ 899,318	$ 876,708
Tier 1 capital (to risk weighted assets), minimum capital requirement	728,019	709,716
Common equity Tier 1 capital (to risk weighted assets), minimum capital requirement	599,545	584,472
Tier 1 capital (to average assets), minimum capital requirement	$ 390,751	$ 388,982
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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