Regulatory Matters - Summary of Capital Amounts, Tier 1 Risk Based and Tier 1 Leveraged Ratios (Detail) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Common equity Tier 1 (to risk weighted assets), Actual Amount	$ 481,277
Total capital (to risk weighted assets), Actual Amount	667,532	$ 578,644
Tier 1 capital (to risk weighted assets), Actual Amount	536,846	437,712
Tier 1 capital (to average assets), Actual Amount	$ 536,846	$ 437,712
Common equity Tier 1 ( to risk weighted assets), Actual Ratio	8.24%
Total capital (to risk weighted assets), Actual Ratio	11.43%	11.09%
Tier 1 capital (to risk weighted assets), Actual Ratio	9.19%	8.39%
Tier 1 capital (to average assets), Actual Ratio	7.27%	6.69%
Common equity Tier 1 (to risk weighted assets), For Capital Adequacy Purposes Amount	$ 262,811
Total capital (to risk weighted assets), For Capital Adequacy Purposes Amount	467,219	$ 417,473
Tier 1 capital (to risk weighted assets), For Capital Adequacy Purposes Amount	350,414	208,737
Tier 1 capital (to average assets), For Capital Adequacy Purposes Amount	$ 295,328	$ 261,622
Common equity Tier 1 (to risk weighted assets), For Capital Adequacy Purposes Ratio	4.50%
Total capital (to risk weighted assets), For Capital Adequacy Purposes Ratio	8.00%	8.00%
Tier 1 capital (to risk weighted assets), For Capital Adequacy Purposes Ratio	6.00%	4.00%
Tier 1 capital (to average assets), For Capital Adequacy Purposes Ratio	4.00%	4.00%
Tier 1 capital (to risk weighted assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Ratio	8.00%
Customers Bank
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Common equity Tier 1 (to risk weighted assets), Actual Amount	$ 549,276
Total capital (to risk weighted assets), Actual Amount	693,099	$ 621,894
Tier 1 capital (to risk weighted assets), Actual Amount	549,276	480,963
Tier 1 capital (to average assets), Actual Amount	$ 549,276	$ 480,963
Common equity Tier 1 ( to risk weighted assets), Actual Ratio	9.45%
Total capital (to risk weighted assets), Actual Ratio	11.92%	11.98%
Tier 1 capital (to risk weighted assets), Actual Ratio	9.45%	9.27%
Tier 1 capital (to average assets), Actual Ratio	7.46%	7.39%
Common equity Tier 1 (to risk weighted assets), For Capital Adequacy Purposes Amount	$ 261,566
Total capital (to risk weighted assets), For Capital Adequacy Purposes Amount	465,007	$ 415,141
Tier 1 capital (to risk weighted assets), For Capital Adequacy Purposes Amount	348,755	207,570
Tier 1 capital (to average assets), For Capital Adequacy Purposes Amount	$ 294,713	$ 260,462
Common equity Tier 1 (to risk weighted assets), For Capital Adequacy Purposes Ratio	4.50%
Total capital (to risk weighted assets), For Capital Adequacy Purposes Ratio	8.00%	8.00%
Tier 1 capital (to risk weighted assets), For Capital Adequacy Purposes Ratio	6.00%	4.00%
Tier 1 capital (to average assets), For Capital Adequacy Purposes Ratio	4.00%	4.00%
Common equity Tier 1 (to risk weighted assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Amount	$ 377,818
Total capital (to risk weighted assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Amount	581,259	$ 518,926
Tier 1 capital (to risk weighted assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Amount	465,007	311,356
Tier 1 capital (to average assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Amount	$ 368,392	$ 325,577
Common equity Tier 1 (to risk weighted assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Ratio	6.50%
Total capital (to risk weighted assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Ratio	10.00%	10.00%
Tier 1 capital (to risk weighted assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Ratio	8.00%	6.00%
Tier 1 capital (to average assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Ratio	5.00%	5.00%