| Document And Entity Information | Jun. 15, 2023 |
| Document Information [Line Items] | |
| Entity, Registrant Name | NSTS Bancorp, Inc. |
| Document, Type | 8-K |
| Document, Period End Date | Jun. 15, 2023 |
| Entity, Incorporation, State or Country Code | DE |
| Entity, File Number | 001-41232 |
| Entity, Tax Identification Number | 87-2522769 |
| Entity, Address, Address Line One | 700 S. Lewis Avenue |
| Entity, Address, City or Town | Waukegan |
| Entity, Address, State or Province | IL |
| Entity, Address, Postal Zip Code | 60085 |
| City Area Code | 847 |
| Local Phone Number | 336-4430 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Title of 12(b) Security | Common Stock |
| Trading Symbol | NSTS |
| Security Exchange Name | NASDAQ |
| Entity, Emerging Growth Company | true |
| Entity, Ex Transition Period | false |
| Amendment Flag | false |
| Entity, Central Index Key | 0001881592 |
