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Regulatory Matters - Narrative (Details)
Dec. 31, 2017
Jan. 01, 2017
Dec. 31, 2016
Jan. 01, 2015
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]        
Capital conservation buffer, excess of minimum capital ratio       2.50%
Maximum buffer, percent of risk weighted assets for 2016 0.625%      
Maximum buffer, percent of risk weighted assets for 2017 1.25%      
Maximum buffer, percent of risk weighted assets for 2018 1.875%      
Maximum buffer, percent of risk weighted assets for 2019 2.50%      
Customers Bancorp, Inc.        
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]        
Common equity Tier 1 (to risk-weighted assets), for capital adequacy purposes ratio 4.50% 5.75% 4.50%  
Tier 1 capital (to risk-weighted assets), for capital adequacy purposes ratio 6.00% 7.25% 6.00%  
Total capital (to risk-weighted assets), for capital adequacy purposes ratio 8.00% 9.25% 8.00%