| Document and Entity Information | Aug. 09, 2022 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Amendment Flag | false |
| Document Period End Date | Aug. 09, 2022 |
| Entity Registrant Name | 1895 Bancorp of Wisconsin, Inc. /MD/ |
| Entity Incorporation, State or Country Code | MD |
| Entity File Number | 333-254135 |
| Entity Tax Identification Number | 61-1993378 |
| Entity Address, Address Line One | 7001 WEST EDGERTON AVENUE |
| Entity Address, City or Town | GREENFIELD |
| Entity Address, State or Province | WI |
| Entity Address, Postal Zip Code | 53220 |
| City Area Code | 414 |
| Local Phone Number | 421-8200 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Entity Emerging Growth Company | true |
| Entity Ex Transition Period | false |
| Entity Central Index Key | 0001847360 |
| Title of 12(b) Security | Common Stock, par value $0.01 per share |
| Trading Symbol | BCOW |
| Security Exchange Name | NASDAQ |
