| Cover | Aug. 06, 2020 |
| Schedule of Capitalization, Equity [Line Items] | |
| Document Type | 8-K |
| Amendment Flag | false |
| Document Period End Date | Aug. 6, 2020 |
| Entity File Number | 001-35542 |
| Entity Registrant Name | CUSTOMERS BANCORP, INC. |
| Entity Central Index Key | 0001488813 |
| Entity Tax Identification Number | 27-2290659 |
| Entity Incorporation, State or Country Code | PA |
| 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 |
| Voting Common Stock, par value $1.00 per share | |
| Schedule of Capitalization, Equity [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 | |
| Schedule of Capitalization, Equity [Line Items] | |
| Title of 12(b) Security | Fixed-to-Floating Rate Non-Cumulative Perpetual Preferred 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 | |
| Schedule of Capitalization, Equity [Line Items] | |
| Title of 12(b) Security | Fixed-to-Floating Rate Non-Cumulative Perpetual Preferred 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 | |
| Schedule of Capitalization, Equity [Line Items] | |
| Title of 12(b) Security | Fixed-to-Floating Rate Non-Cumulative Perpetual Preferred 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 | |
| Schedule of Capitalization, Equity [Line Items] | |
| Title of 12(b) Security | Fixed-to-Floating Rate Non-Cumulative Perpetual Preferred Stock, Series F, par value $1.00 per share |
| Trading Symbol | CUBI/PF |
| Security Exchange Name | NYSE |
| 5.375% Subordinated Notes due 2034 | |
| Schedule of Capitalization, Equity [Line Items] | |
| Title of 12(b) Security | 5.375% Subordinated Notes due 2034 |
| Trading Symbol | CUBB |
| Security Exchange Name | NYSE |
