Basis of Presentation	6 Months Ended
Jun. 30, 2026
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Presentation	(1) Basis of Presentation The accompanying unaudited condensed consolidated financial statements of Fastenal Company and subsidiaries (the 'Company,' 'Fastenal,' 'we,' 'our,' or 'us') have been prepared in accordance with U.S. generally accepted accounting principles (GAAP) for interim financial information. They do not include all information and footnotes required by U.S. GAAP for a complete set of financial statements. However, except as described herein, there has been no material change in the information disclosed in the Notes to Consolidated Financial Statements included in our consolidated financial statements as of and for the year ended December 31, 2025. In the opinion of management, all adjustments (consisting of normal recurring adjustments) considered necessary for a fair statement have been included. Percentages, values, and dollar change calculations, which are based on non-rounded dollar values, may not be able to be recalculated or footed using the dollar values in this document due to the rounding of those dollar values. Recently Issued Accounting Pronouncements In November 2024, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) 2024-03, Disaggregation of Income Statement Expenses (DISE), which specifies new disclosure requirements, including the composition of certain income statement expense line items (such as purchases of inventory, employee compensation, and 'other expenses') and a separate disclosure for selling expenses. This change is effective for fiscal years beginning after December 15, 2026, and interim periods beginning after December 15, 2027, however, early adoption is permitted. We are currently evaluating the impact that the adoption of ASU 2024-03 will have on our consolidated financial statements and disclosures and anticipate adoption in 2027.

Basis of Presentation

6 Months Ended

Jun. 30, 2026

Organization, Consolidation and Presentation of Financial Statements [Abstract]

(1) Basis of Presentation

The accompanying unaudited condensed consolidated financial statements of Fastenal Company and subsidiaries (the 'Company,' 'Fastenal,' 'we,' 'our,' or 'us') have been prepared in accordance with U.S. generally accepted accounting principles (GAAP) for interim financial information. They do not include all information and footnotes required by U.S. GAAP for a complete set of financial statements. However, except as described herein, there has been no material change in the information disclosed in the Notes to Consolidated Financial Statements included in our consolidated financial statements as of and for the year ended December 31, 2025. In the opinion of management, all adjustments (consisting of normal recurring adjustments) considered necessary for a fair statement have been included. Percentages, values, and dollar change calculations, which are based on non-rounded dollar values, may not be able to be recalculated or footed using the dollar values in this document due to the rounding of those dollar values.

Recently Issued Accounting Pronouncements

In November 2024, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) 2024-03, Disaggregation of Income Statement Expenses (DISE), which specifies new disclosure requirements, including the composition of certain income statement expense line items (such as purchases of inventory, employee compensation, and 'other expenses') and a separate disclosure for selling expenses. This change is effective for fiscal years beginning after December 15, 2026, and interim periods beginning after December 15, 2027, however, early adoption is permitted. We are currently evaluating the impact that the adoption of ASU 2024-03 will have on our consolidated financial statements and disclosures and anticipate adoption in 2027.