Shareholders Equity and Regulatory Matters - Schedule of comparison of the actual capital amounts and ratios (Details) $ in Thousands	Sep. 30, 2025 USD ($)	Dec. 31, 2024 USD ($)
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Total capital (to risk weighted assets), Actual, Amount	$ 609,476	$ 559,871
Total capital (to risk weighted assets), Actual, Ratio	0.129	0.1268
Total capital (to risk weighted assets), For Capital Adequacy Purposes, Amount	$ 496,174	$ 463,735
Total capital (to risk weighted assets), For Capital Adequacy Purposes, Ratio	0.105	0.105
Tier 1 capital (to risk weighted assets), Actual, Amount	$ 484,235	$ 437,369
Tier 1 capital (to risk weighted assets), Actual, Ratio	0.1025	0.099
Tier 1 capital (to risk weighted assets), For Capital Adequacy Purposes, Amount	$ 401,665	$ 375,405
Tier 1 capital (to risk weighted assets), For Capital Adequacy Purposes, Ratio	0.085	0.085
Tier 1 capital (to average assets), Actual, Amount	$ 484,235	$ 437,369
Tier 1 capital (to average assets), Actual, Ratio	0.0955	0.0912
Tier 1 capital (to average assets), For Capital Adequacy Purposes, Amount	$ 202,743	$ 191,793
Tier 1 capital (to average assets), For Capital Adequacy Purposes, Ratio	0.04	0.04
Common equity tier 1 (to risk weighted assets), Actual, Amount	$ 418,075	$ 371,209
Common equity tier 1 (to risk weighted assets), Actual, Ratio	0.0885	0.0841
Common equity tier 1 (to risk weighted assets), For Capital Adequacy Purposes, Amount	$ 330,783	$ 309,157
Common equity tier 1 (to risk weighted assets), For Capital Adequacy Purposes, Ratio	0.07	0.07
THIRD COAST BANK
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Total capital (to risk weighted assets), Actual, Amount	$ 639,050	$ 586,569
Total capital (to risk weighted assets), Actual, Ratio	0.1353	0.1329
Total capital (to risk weighted assets), For Capital Adequacy Purposes, Amount	$ 495,833	$ 463,262
Total capital (to risk weighted assets), For Capital Adequacy Purposes, Ratio	0.105	0.105
Total capital (to risk weighted assets), To Be Well Capitalized Under Prompt Corrective Action Provisions, Amount	$ 472,222	$ 441,202
Total capital (to risk weighted assets), To Be Well Capitalized Under Prompt Corrective Action Provisions, Ratio	0.10	0.10
Tier 1 capital (to risk weighted assets), Actual, Amount	$ 594,722	$ 544,826
Tier 1 capital (to risk weighted assets), Actual, Ratio	0.1259	0.1235
Tier 1 capital (to risk weighted assets), For Capital Adequacy Purposes, Amount	$ 401,389	$ 375,021
Tier 1 capital (to risk weighted assets), For Capital Adequacy Purposes, Ratio	0.085	0.085
Tier 1 capital (to risk weighted assets), To Be Well Capitalized Under Prompt Corrective Action Provisions, Amount	$ 377,778	$ 352,961
Tier 1 capital (to risk weighted assets), To Be Well Capitalized Under Prompt Corrective Action Provisions, Ratio	0.08	0.08
Tier 1 capital (to average assets), Actual, Amount	$ 594,722	$ 544,826
Tier 1 capital (to average assets), Actual, Ratio	0.1175	0.1137
Tier 1 capital (to average assets), For Capital Adequacy Purposes, Amount	$ 202,508	$ 191,606
Tier 1 capital (to average assets), For Capital Adequacy Purposes, Ratio	0.04	0.04
Tier 1 capital (to average assets), To Be Well Capitalized Under Prompt Corrective Action Provisions, Amount	$ 253,135	$ 239,507
Tier 1 capital (to average assets), To Be Well Capitalized Under Prompt Corrective Action Provisions, Ratio	0.05	0.05
Common equity tier 1 (to risk weighted assets), Actual, Amount	$ 594,722	$ 544,826
Common equity tier 1 (to risk weighted assets), Actual, Ratio	0.1259	0.1235
Common equity tier 1 (to risk weighted assets), For Capital Adequacy Purposes, Amount	$ 330,555	$ 308,841
Common equity tier 1 (to risk weighted assets), For Capital Adequacy Purposes, Ratio	0.07	0.07
Common equity tier 1 (to risk weighted assets), To Be Well Capitalized Under Prompt Corrective Action Provisions, Amount	$ 306,944	$ 286,781
Common equity tier 1 (to risk weighted assets), To Be Well Capitalized Under Prompt Corrective Action Provisions, Ratio	0.065	0.065