Significant Accounting Policies (Policies)	9 Months Ended
Significant Accounting Policies (Policies)	Sep. 30, 2024
Accounting Policies [Abstract]
Nature of Operations [Policy Text Block]	Nature of Operations NSTS Bancorp, Inc. (“NSTS” or the “Company”, “we” or “our”) was formed to serve as the stock holding company for North Shore Trust and Savings (the “Bank”) in connection with the conversion of North Shore Trust and Savings, NSTS Financial Corporation and North Shore MHC, into the stock form of organization, which was completed on January 18, 2022. Shares of NSTS Bancorp, Inc. stock began trading on January 19, 2022 on the Nasdaq Capital Market under the trading symbol "NSTS." The Bank operates primarily out of three bank branch locations in the northern suburbs of Chicago, Illinois. In efforts to expand our loan originations within the Chicagoland area, the Bank also has three loan production offices, located in Chicago, Aurora and Plainfield, Illinois. The lending team operates as Oak Leaf Community Mortgage, powered by North Shore Trust and Savings. The Bank offers a variety of financial services to customers in our surrounding community. Financial services consist primarily of 1-4 family mortgage loans, savings accounts, and certificate of deposit accounts. There are no significant concentrations of loans to any one industry or customer. The Bank’s exposure to credit risk is significantly affected by changes in the economy in the Bank’s market area.
Basis of Accounting, Policy [Policy Text Block]	Basis of Presentation The accompanying unaudited Consolidated Financial Statements were prepared in accordance with GAAP and the instructions to Form 10-Q and Rule 10-01 of Regulation S-X. Accordingly, they do not include all of the information and footnotes required by GAAP for complete financial statements and should be read in conjunction with NSTS Bancorp, Inc.’s Consolidated Financial Statements and footnotes thereto included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2023. The unaudited Consolidated Financial Statements include the accounts of the Company and its wholly-owned subsidiaries. All significant intercompany balances and transactions have been eliminated in consolidation. Management is required to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenue and expenses during the reporting period. Actual results may vary from those estimates. Material estimates that could significantly change in the near-term include the adequacy of the allowance for credit losses, determination of the valuation allowance on deferred tax assets and the valuation of investment securities and the related tax effect. The results of operations for the three and nine months ended September 30, 2024, are not necessarily indicative of results that may be expected for any other interim period or the entire fiscal year ending December 31, 2024. Certain amounts in prior year financial statements have been reclassified to conform to the current presentation. Subsequent events have been evaluated through the date of issuance of the unaudited Consolidated Financial Statements. No significant subsequent events have occurred through this date requiring adjustment to the financial statements or disclosures. In March 2024, the FASB issued ASU No. 2024-01, “Compensation—Stock Compensation (Topic 718): Scope Applications of Profits Interests and Similar Awards” (ASU 2024-01). ASU 2024-01 adds an example to Topic 718 which illustrates how to apply the scope guidance to determine whether profits interests and similar awards should be accounted for as share-based payment arrangements under Topic 718 or under other U.S. GAAP. ASU 2024-01 is effective for annual periods beginning after December 15, 2025, although early adoption is permitted. Upon adoption, ASU 2024-01 is not expected to have an impact on the Company’s consolidated balance sheets or consolidated statements of income.

NSTS Bancorp, Inc. 10-Q