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REGULATORY CAPITAL - Summary of Capital Amounts, Tier 1 Risk Based and Tier 1 Leveraged Ratios (Detail) - USD ($) $ in Thousands | Sep. 30, 2025 | Dec. 31, 2024
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Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items] |  |
Common equity Tier 1 capital (to risk weighted assets), Actual Amount | $ 2,089,260 | $ 1,803,601
Tier 1 capital (to risk weighted assets), Actual Amount | 2,171,461 | 1,941,394
Total capital (to risk weighted assets), Actual Amount | 2,466,429 | 2,219,984
Tier 1 capital (to average assets), Actual Amount | $ 2,171,461 | $ 1,941,394
Common equity Tier 1 (to risk weighted assets), Actual Ratio | 12.999% | 12.087%
Tier 1 capital (to risk weighted assets), Actual Ratio | 0.13510 | 0.13011
Total capital (to risk weighted assets), Actual Ratio | 0.15345 | 0.14878
Tier 1 capital (to average assets), Actual Ratio | 0.09034 | 0.08694
Common equity Tier 1 capital (to risk weighted assets), For Capital Adequacy Purposes Amount | $ 723,277 | $ 671,841
Tier 1 capital (to risk weighted assets), For Capital Adequacy Purposes Amount | 964,369 | 895,308
Total capital (to risk weighted assets), For Capital Adequacy Purposes Amount | 1,285,825 | 1,193,744
Tier 1 capital (to average assets), For Capital Adequacy Purposes Amount | $ 961,444 | $ 893,254
Common equity Tier 1 (to risk weighted assets), For Capital Adequacy Purposes Ratio | 4.50% | 4.50%
Tier 1 capital (to risk weighted assets), For Capital Adequacy Purposes Ratio | 0.06000 | 0.06000
Total capital (to risk weighted assets), For Capital Adequacy Purposes Ratio | 0.08000 | 0.08000
Tier 1 capital (to average assets), For Capital Adequacy Purposes Ratio | 0.04000 | 0.04000
Common equity Tier 1 (to risk weighted assets), for Basel III amount | $ 1,125,097 | $ 1,044,526
Tier 1 (to risk weighted assets) Required for Basel III amount | 1,366,189 | 1,268,353
Total capital (to risk weighted assets), for Basel III amount | 1,687,646 | 1,566,789
Tier 1 (to risk average assets), for Basel III amount | $ 961,444 | $ 893,254
Common equity Tier 1 (to risk weighted assets), for Basel III ratio | 7.00% | 7.00%
Tier 1 capital (to risk weighted assets), for Basel III ratio | 8.50% | 8.50%
Total capital (to risk weighted assets), for Basel III ratio | 10.50% | 10.50%
Tier 1 capital (to average assets), for Basel III ratio | 4.00% | 4.00%
Customers Bank |  |
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items] |  |
Common equity Tier 1 capital (to risk weighted assets), Actual Amount | $ 2,121,804 | $ 1,930,951
Tier 1 capital (to risk weighted assets), Actual Amount | 2,121,804 | 1,930,951
Total capital (to risk weighted assets), Actual Amount | 2,343,688 | 2,136,594
Tier 1 capital (to average assets), Actual Amount | $ 2,121,804 | $ 1,930,951
Common equity Tier 1 (to risk weighted assets), Actual Ratio | 13.222% | 12.955%
Tier 1 capital (to risk weighted assets), Actual Ratio | 0.13222 | 0.12955
Total capital (to risk weighted assets), Actual Ratio | 0.14604 | 0.14335
Tier 1 capital (to average assets), Actual Ratio | 0.08835 | 0.08652
Common equity Tier 1 capital (to risk weighted assets), For Capital Adequacy Purposes Amount | $ 722,164 | $ 670,719
Tier 1 capital (to risk weighted assets), For Capital Adequacy Purposes Amount | 962,885 | 894,292
Total capital (to risk weighted assets), For Capital Adequacy Purposes Amount | 1,283,846 | 1,192,390
Tier 1 capital (to average assets), For Capital Adequacy Purposes Amount | $ 960,668 | $ 892,755
Common equity Tier 1 (to risk weighted assets), For Capital Adequacy Purposes Ratio | 4.50% | 4.50%
Tier 1 capital (to risk weighted assets), For Capital Adequacy Purposes Ratio | 0.06000 | 0.06000
Total capital (to risk weighted assets), For Capital Adequacy Purposes Ratio | 0.08000 | 0.08000
Tier 1 capital (to average assets), For Capital Adequacy Purposes Ratio | 0.04000 | 0.04000
Common equity Tier 1 Capital (to risk weighted assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Amount | $ 1,043,125 | $ 968,817
Tier 1 capital (to risk weighted assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Amount | 1,283,846 | 1,192,390
Total capital (to risk weighted assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Amount | 1,604,808 | 1,490,487
Tier 1 capital (to average assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Amount | $ 1,200,835 | $ 1,115,944
Common equity Tier 1 (to risk weighted assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Ratio | 6.50% | 6.50%
Tier 1 capital (to risk weighted assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Ratio | 0.08000 | 0.08000
Total capital (to risk weighted assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Ratio | 0.10000 | 0.10000
Tier 1 capital (to average assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Ratio | 0.05000 | 0.05000
Common equity Tier 1 (to risk weighted assets), for Basel III amount | $ 1,123,365 | $ 1,043,341
Tier 1 (to risk weighted assets) Required for Basel III amount | 1,364,087 | 1,266,914
Total capital (to risk weighted assets), for Basel III amount | 1,685,048 | 1,565,012
Tier 1 (to risk average assets), for Basel III amount | $ 960,668 | $ 892,755
Common equity Tier 1 (to risk weighted assets), for Basel III ratio | 7.00% | 7.00%
Tier 1 capital (to risk weighted assets), for Basel III ratio | 8.50% | 8.50%
Total capital (to risk weighted assets), for Basel III ratio | 10.50% | 10.50%
Tier 1 capital (to average assets), for Basel III ratio | 4.00% | 4.00%

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