| Document and Entity Information | Jul. 28, 2021 | Jan. 27, 2021 |
| Entity Information [Line Items] | ||
| Amendment Flag | false | |
| Entity Incorporation, State or Country Code | PA | |
| Document Type | 8-K | |
| Document Period End Date | Jul. 28, 2021 | |
| Entity Registrant Name | Customers Bancorp, Inc. | |
| Entity File Number | 001-35542 | |
| Entity Tax Identification Number | 27-2290659 | |
| Entity Address, Address Line One | 701 Reading Avenue | |
| Entity Address, City or Town | West Reading | |
| Entity Address, State or Province | PA | |
| Entity Address, Postal Zip Code | 19611 | |
| City Area Code | 610 | |
| Local Phone Number | 933-2000 | |
| Written Communications | false | |
| Soliciting Material | false | |
| Pre-commencement Tender Offer | false | |
| Pre-commencement Issuer Tender Offer | false | |
| Entity Emerging Growth Company | false | |
| Entity Central Index Key | 0001488813 | |
| Voting Common Stock, par value $1.00 per share | New York Stock Exchange | ||
| Entity Information [Line Items] | ||
| Title of 12(b) Security | Voting Common Stock, par value $1.00 per share | |
| Trading Symbol | CUBI | |
| Security Exchange Name | NYSE | |
| Fixed-to-Floating Rate Non-Cumulative Perpetual Preferred Stock, Series C, par value $1.00 per share | New York Stock Exchange | ||
| Entity Information [Line Items] | ||
| Title of 12(b) Security | Fixed-to-Floating Rate Non-Cumulative PerpetualPreferred Stock, Series C, par value $1.00 per share | |
| Trading Symbol | CUBI/PC | |
| Security Exchange Name | NYSE | |
| Fixed-to-Floating Rate Non-Cumulative Perpetual Preferred Stock, Series D, par value $1.00 per share | New York Stock Exchange | ||
| Entity Information [Line Items] | ||
| Title of 12(b) Security | Fixed-to-Floating Rate Non-Cumulative PerpetualPreferred Stock, Series D, par value $1.00 per share | |
| Trading Symbol | CUBI/PD | |
| Security Exchange Name | NYSE | |
| Fixed-to-Floating Rate Non-Cumulative Perpetual Preferred Stock, Series E, par value $1.00 per share | New York Stock Exchange | ||
| Entity Information [Line Items] | ||
| Title of 12(b) Security | Fixed-to-Floating Rate Non-Cumulative PerpetualPreferred Stock, Series E, par value $1.00 per share | |
| Trading Symbol | CUBI/PE | |
| Security Exchange Name | NYSE | |
| Fixed-to-Floating Rate Non-Cumulative Perpetual Preferred Stock, Series F, par value $1.00 per share | New York Stock Exchange | ||
| Entity Information [Line Items] | ||
| Title of 12(b) Security | Fixed-to-Floating Rate Non-Cumulative PerpetualPreferred Stock, Series F, par value $1.00 per share | |
| Trading Symbol | CUBI/PF | |
| Security Exchange Name | NYSE | |
| Subordinated Debt [Member] | New York Stock Exchange | ||
| Entity Information [Line Items] | ||
| Title of 12(b) Security | 5.375% Subordinated Notes due 2034 | |
| Trading Symbol | CUBB | |
| Security Exchange Name | NYSE |
