Business Overview and Summary of Significant Accounting Policies	12 Months Ended
Dec. 31, 2021
Accounting Policies [Abstract]
Business Overview and Summary of Significant Accounting Policies	Note 1. Business Overview and Summary of Significant Accounting Policies Business Overview Fastenal is a leader in the wholesale distribution of industrial and construction supplies. We distribute these supplies through a network of branches and Onsite locations. Collectively we refer to our branches and Onsite locations as in-market locations. We have over 3,200 in-market locations located primarily in North America. Principles of Consolidation The consolidated financial statements include the accounts of Fastenal Company and its subsidiaries (collectively referred to as Fastenal or by terms such as we, our, or us). All material intercompany balances and transactions have been eliminated in consolidation. Revenue Recognition Net sales include products and shipping and handling charges, net of estimates for product returns and any related sales incentives. Revenue is measured as the amount of consideration we expect to receive in exchange for transferring products. All revenue is recognized when we satisfy our performance obligations under the contract. We recognize revenue by transferring the promised products to the customer, with the majority of revenue recognized at the point in time the customer obtains control of the products. We recognize revenue for shipping and handling charges at the time the products are delivered to or picked up by the customer. We estimate product returns based on historical return rates. Using probability assessments, which are based on known inputs at year-end, we estimate sales incentives expected to be paid over the term of the contract. The majority of our contracts have a single performance obligation and are short term in nature. Sales taxes and value added taxes in foreign jurisdictions that are collected from customers and remitted to governmental authorities are accounted for on a net basis and therefore are excluded from net sales. Accounts Receivable Credit is extended based upon an evaluation of the customers' financial condition. Accounts receivable are stated at their estimated net realizable value. The allowance for credit losses is based on an income statement approach which adjusts the ending balance sheet to take into consideration expected losses over the contractual lives of the receivables, considering factors such as historical data as a basis for future expected losses. Foreign Currency Translation and Transactions The functional currency of our foreign operations is typically the applicable local currency. The functional currency is translated into United States dollars for balance sheet accounts, except retained earnings, using current exchange rates as of the balance sheet date, for retained earnings at historical exchange rates, and for revenue and expense accounts using a weighted average exchange rate during the applicable period. The translation adjustments are deferred as a separate component of stockholders' equity captioned accumulated other comprehensive income (loss). Gains or losses resulting from transactions denominated in foreign currencies are included in cost of sales or operating and administrative expenses. Cash and Cash Equivalents We consider all investments purchased with original maturities of three months or less to be cash equivalents. Inventories Inventories, consisting of finished goods merchandise held for resale, are stated at the lower of cost (first in, first out method) or net realizable value. We record valuation adjustments for excess, slow-moving, and obsolete inventory that are equal to the difference between the cost and estimated net realizable value for that inventory. These estimates are based on a review and comparison of the current inventory levels to projected and historical sales of inventory. Property and Equipment Property and equipment are stated at cost. Depreciation on property and equipment is provided for using the straight-line method over the anticipated economic useful lives of the related property. Long-lived assets are reviewed for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. If circumstances require a long-lived asset or asset group be tested for possible impairment, we first compare undiscounted cash flows expected to be generated by the asset or asset group to its carrying value. If the carrying value of the long-lived asset or asset group is not recoverable on an undiscounted cash flow basis, an impairment is recognized to the extent the carrying value exceeds its fair value. Fair value is determined through various valuation techniques including discounted cash flow models, quoted market values, and third-party independent appraisals, as considered necessary. There were no impairments recorded during any of the three years reported in these consolidated financial statements. Leases We determine if an arrangement contains a lease at inception. Operating leases are included in our operating lease right-of-use (ROU) assets, the current portion of operating lease liabilities, and the operating lease liabilities in our Consolidated Balance Sheets. The ROU assets represent our right to control the use of an underlying asset for the lease term, and lease liabilities represent our obligation to make lease payments arising from the lease. Operating lease ROU assets and lease liabilities are recognized at commencement date based on the present value of lease payments over the lease term. The operating lease ROU assets also include any prepaid lease payments made and exclude lease incentives. Lease expense is recognized on a straight-line basis over the lease term. Many of our leases include both lease (e.g., fixed payments including rent, taxes, and insurance costs) and nonlease components (e.g., common-area or other maintenance costs) which are accounted for as a single lease component as we have elected the practical expedient to group lease and nonlease components for all leases. Our pick-up truck leases typically have a non-cancelable lease term of less than one year and therefore, we have elected the practical expedient to exclude these short-term leases from our ROU assets and lease liabilities. Most leases include one or more options to renew. The exercise of lease renewal options is typically at our sole discretion; therefore, the majority of renewals to extend the lease terms are not included in our ROU assets and lease liabilities as they are not reasonably certain of exercise. We regularly evaluate the renewal options and when they are reasonably certain of exercise, we include the renewal period in our lease term. As most of our leases do not provide an implicit rate, we use our incremental borrowing rate based on the information available at the lease commencement date in determining the present value of the lease payments. We have a centrally managed treasury function; therefore, based on the applicable lease terms and the current economic environment, we apply a portfolio approach for determining the incremental borrowing rate. Other Long-Lived Assets Other assets consist of prepaid deposits, goodwill, and other definite-lived intangible assets. Goodwill represents the excess of the purchase price over the fair value of net assets acquired. Goodwill is reviewed for impairment annually. The identifiable intangible assets are amortized on a straight-line basis over their estimated life. On March 30, 2020 we purchased certain assets of Apex for $125.0, including identifiable intangible assets totaling $123.8, with a weighted average amortization period of approximately 19.4 years. Accounting Estimates The preparation of the consolidated financial statements in conformity with U.S. GAAP requires us to make estimates and assumptions that affect the reported amounts of assets and liabilities, revenues and expenses, and the disclosure of contingent liabilities. Actual results could differ from those estimates. Insurance Reserves We are self-insured for certain losses relating to workers' compensation, automobile, health, and general liability costs. Specific stop-loss coverage is provided for catastrophic claims in order to limit exposure to significant claims. Self-insurance liabilities are based on our estimate of reported claims and claims incurred but not yet reported. Product Warranties We offer a basic limited warranty for certain of our products. The specific terms and conditions of those warranties vary depending upon the product sold. We typically recoup these costs through product warranties we hold with the original equipment manufacturers. Our warranty expense has historically been minimal. Stock-Based Compensation We estimate the value of stock option grants using a Black-Scholes valuation model. Stock-based compensation expense is recognized on a straight-line basis over the vesting period. Our stock-based compensation expense is recorded in operating and administrative expenses. Income Taxes We account for income taxes under the asset and liability method. Under this method, deferred tax assets and liabilities are recognized for the future tax consequences attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax bases. Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the years in which those temporary differences are expected to be recovered or settled. The effect on deferred tax assets and liabilities of a change in tax rates is recognized in income in the period that includes the enactment date. We recognize the effect of income tax positions only if those positions are more likely than not to be sustained. Recognized income tax positions are measured at the largest amount that is greater than 50% likely of being realized. Changes in recognition or measurement are reflected in the period in which the change in judgment occurs. We record interest and penalties related to unrecognized tax benefits in income tax expense. Earnings Per Share Basic net earnings per share is calculated using net earnings available to common stockholders divided by the weighted average number of shares of common stock outstanding during the year. Diluted net earnings per share is similar to basic net earnings per share except that the weighted average number of shares of common stock outstanding includes the incremental shares assumed to be issued upon the exercise of stock options considered to be 'in-the-money' (i.e., when the market price of our stock is greater than the exercise price of our outstanding stock options). Segment Reporting We have determined that for our North American regions we meet the aggregation criteria outlined in the accounting standards as these regions have similar: (1) economic characteristics, (2) products and services, (3) customers, (4) distribution channels, and (5) regulatory environments. Considering the insignificance of our operations outside of North America, we report as a single business segment. Impact of COVID-19 The COVID-19 pandemic has likely influenced various trends the company is currently experiencing. These include supply chain disruptions and labor shortages, and a modest shift in our mix to include more safety products. Evaluating 2021 is challenging given the impacts of the pandemic on the company in the year-earlier period. However, in contrast to much of the preceding one to two years, we are currently seeing a narrower impact on our business related directly to the COVID-19 pandemic, as economic activity has recovered and customer and product mix has reverted back to close to pre-pandemic levels. We believe current financial results are more reflective of traditional economic and marketplace dynamics than of pandemic-related issues such as facility restrictions, labor force illness, and personal protective equipment (PPE) demand. The primary exception to this normalization trend is in the signings of our Onsite and Fastenal Managed Inventory (FMI), which have yet to recover to pre-pandemic levels. To the extent that COVID-19 infections and/or interventions continue to meaningfully influence the marketplace, on a national, local, or business-specific basis, this can either directly impact or indirectly influence access to customer facilities and decision-makers, and lengthen the sales cycle for certain of our solutions. However, it is possible the COVID-19 pandemic, particularly in light of variant strains of the virus, could further impact our operations and the operations of our suppliers and vendors as a result of quarantines, facility closures, illnesses, and travel and logistics restrictions. The extent to which the COVID-19 pandemic impacts our business, results of operations, and financial condition will depend on future developments, which are highly uncertain and cannot be predicted, including, but not limited to, the resumption of high levels of infection and hospitalization, the resulting impact on our customers, suppliers, and vendors, the remedial actions and stimulus measures adopted by federal, state, and local governments, and to what extent normal economic and operating conditions are impacted. We cannot reasonably estimate the future impact at this time. Stock Split On April 17, 2019, the board of directors approved a two-for-one stock split of the company's outstanding common stock. Holders of the company's common stock, par value $0.01 per share, at the close of business on May 2, 2019, received one additional share of common stock for every share of common stock they owned. The stock split took effect at the close of business on May 22, 2019. All historical common stock share and per share information for all periods presented in the accompanying consolidated financial statements and notes thereto have been retroactively adjusted to reflect the stock split. Immaterial Revision The prior period balances for additional paid-in capital and common stock have been updated in both the Consolidated Balance Sheets and Consolidated Statements of Stockholders' Equity to reflect the impact of an immaterial correction which reclassified $2.9 from additional paid-in capital to common stock in connection with the 2019 stock split. Recently Issued Accounting Pronouncements In March 2020, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) 2020-04, Reference Rate Reform (Topic 848): Facilitation of the Effects of Reference Rate Reform on Financial Reporting, which provides temporary optional expedients and exceptions to U.S. GAAP on contract modifications, hedging relationships, and other transactions affected by reference rate reform to ease entities' financial reporting burdens as the market transitions from the London Interbank Offered Rate (LIBOR) and other interbank offered rates to alternative reference rates. The guidance was effective upon issuance and may be applied prospectively to contract modifications made, hedging relationships entered into, and other transactions affected by reference rate reform, evaluated on or before December 31, 2022, beginning during the reporting period in which the guidance has been elected. We do not have any receivables, hedging relationships, or lease agreements that reference LIBOR or another reference rate expected to be discontinued. We are currently evaluating the impact of the new guidance on our consolidated financial statements; however, we have determined that, of our current debt commitments as outlined in detail in Note 9 'Debt Commitments', only the obligations described under Unsecured Revolving Credit Facility in Note 9 would be impacted by ASU 2020-04. Our Senior Unsecured Promissory Notes Payable described in Note 9 each have fixed interest rates.

Fastenal is a leader in the wholesale distribution of industrial and construction supplies. We distribute these supplies through a network of branches and Onsite locations. Collectively we refer to our branches and Onsite locations as in-market locations. We have over 3,200 in-market locations located primarily in North America.

Net sales include products and shipping and handling charges, net of estimates for product returns and any related sales incentives. Revenue is measured as the amount of consideration we expect to receive in exchange for transferring products. All revenue is recognized when we satisfy our performance obligations under the contract. We recognize revenue by transferring the promised products to the customer, with the majority of revenue recognized at the point in time the customer obtains control of the products. We recognize revenue for shipping and handling charges at the time the products are delivered to or picked up by the customer. We estimate product returns based on historical return rates. Using probability assessments, which are based on known inputs at year-end, we estimate sales incentives expected to be paid over the term of the contract. The majority of our contracts have a single performance obligation and are short term in nature. Sales taxes and value added taxes in foreign jurisdictions that are collected from customers and remitted to governmental authorities are accounted for on a net basis and therefore are excluded from net sales.

Credit is extended based upon an evaluation of the customers' financial condition. Accounts receivable are stated at their estimated net realizable value. The allowance for credit losses is based on an income statement approach which adjusts the ending balance sheet to take into consideration expected losses over the contractual lives of the receivables, considering factors such as historical data as a basis for future expected losses.

The functional currency of our foreign operations is typically the applicable local currency. The functional currency is translated into United States dollars for balance sheet accounts, except retained earnings, using current exchange rates as of the balance sheet date, for retained earnings at historical exchange rates, and for revenue and expense accounts using a weighted average exchange rate during the applicable period. The translation adjustments are deferred as a separate component of stockholders' equity captioned accumulated other comprehensive income (loss). Gains or losses resulting from transactions denominated in foreign currencies are included in cost of sales or operating and administrative expenses.

Inventories, consisting of finished goods merchandise held for resale, are stated at the lower of cost (first in, first out method) or net realizable value. We record valuation adjustments for excess, slow-moving, and obsolete inventory that are equal to the difference between the cost and estimated net realizable value for that inventory. These estimates are based on a review and comparison of the current inventory levels to projected and historical sales of inventory.

Property and equipment are stated at cost. Depreciation on property and equipment is provided for using the straight-line method over the anticipated economic useful lives of the related property. Long-lived assets are reviewed for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. If

circumstances require a long-lived asset or asset group be tested for possible impairment, we first compare undiscounted cash flows expected to be generated by the asset or asset group to its carrying value. If the carrying value of the long-lived asset or asset group is not recoverable on an undiscounted cash flow basis, an impairment is recognized to the extent the carrying value exceeds its fair value. Fair value is determined through various valuation techniques including discounted cash flow models, quoted market values, and third-party independent appraisals, as considered necessary. There were no impairments recorded during any of the three years reported in these consolidated financial statements.

The ROU assets represent our right to control the use of an underlying asset for the lease term, and lease liabilities represent our obligation to make lease payments arising from the lease. Operating lease ROU assets and lease liabilities are recognized at commencement date based on the present value of lease payments over the lease term. The operating lease ROU assets also include any prepaid lease payments made and exclude lease incentives. Lease expense is recognized on a straight-line basis over the lease term.

Many of our leases include both lease (e.g., fixed payments including rent, taxes, and insurance costs) and nonlease components (e.g., common-area or other maintenance costs) which are accounted for as a single lease component as we have elected the practical expedient to group lease and nonlease components for all leases. Our pick-up truck leases typically have a non-cancelable lease term of less than one year and therefore, we have elected the practical expedient to exclude these short-term leases from our ROU assets and lease liabilities.

Most leases include one or more options to renew. The exercise of lease renewal options is typically at our sole discretion; therefore, the majority of renewals to extend the lease terms are not included in our ROU assets and lease liabilities as they are not reasonably certain of exercise. We regularly evaluate the renewal options and when they are reasonably certain of exercise, we include the renewal period in our lease term.

As most of our leases do not provide an implicit rate, we use our incremental borrowing rate based on the information available at the lease commencement date in determining the present value of the lease payments. We have a centrally managed treasury function; therefore, based on the applicable lease terms and the current economic environment, we apply a portfolio approach for determining the incremental borrowing rate.

Other assets consist of prepaid deposits, goodwill, and other definite-lived intangible assets. Goodwill represents the excess of the purchase price over the fair value of net assets acquired. Goodwill is reviewed for impairment annually. The identifiable intangible assets are amortized on a straight-line basis over their estimated life.

The preparation of the consolidated financial statements in conformity with U.S. GAAP requires us to make estimates and assumptions that affect the reported amounts of assets and liabilities, revenues and expenses, and the disclosure of contingent liabilities. Actual results could differ from those estimates.

We are self-insured for certain losses relating to workers' compensation, automobile, health, and general liability costs. Specific stop-loss coverage is provided for catastrophic claims in order to limit exposure to significant claims. Self-insurance liabilities are based on our estimate of reported claims and claims incurred but not yet reported.

We offer a basic limited warranty for certain of our products. The specific terms and conditions of those warranties vary depending upon the product sold. We typically recoup these costs through product warranties we hold with the original equipment manufacturers. Our warranty expense has historically been minimal.

We account for income taxes under the asset and liability method. Under this method, deferred tax assets and liabilities are recognized for the future tax consequences attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax bases. Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the years in which those temporary differences are expected to be recovered or settled. The effect on deferred tax assets and liabilities of a change in tax rates is recognized in income in the period that includes the enactment date.

We recognize the effect of income tax positions only if those positions are more likely than not to be sustained. Recognized income tax positions are measured at the largest amount that is greater than 50% likely of being realized. Changes in recognition or measurement are reflected in the period in which the change in judgment occurs. We record interest and penalties related to unrecognized tax benefits in income tax expense.

Basic net earnings per share is calculated using net earnings available to common stockholders divided by the weighted average number of shares of common stock outstanding during the year. Diluted net earnings per share is similar to basic net earnings per share except that the weighted average number of shares of common stock outstanding includes the incremental shares assumed to be issued upon the exercise of stock options considered to be 'in-the-money' (i.e., when the market price of our stock is greater than the exercise price of our outstanding stock options).

We have determined that for our North American regions we meet the aggregation criteria outlined in the accounting standards as these regions have similar: (1) economic characteristics, (2) products and services, (3) customers, (4) distribution channels, and (5) regulatory environments. Considering the insignificance of our operations outside of North America, we report as a single business segment.

The COVID-19 pandemic has likely influenced various trends the company is currently experiencing. These include supply chain disruptions and labor shortages, and a modest shift in our mix to include more safety products. Evaluating 2021 is challenging given the impacts of the pandemic on the company in the year-earlier period. However, in contrast to much of the preceding one to two years, we are currently seeing a narrower impact on our business related directly to the COVID-19 pandemic, as economic activity has recovered and customer and product mix has reverted back to close to pre-pandemic levels. We believe current financial results are more reflective of traditional economic and marketplace dynamics than of pandemic-related issues such as facility restrictions, labor force illness, and personal protective equipment (PPE) demand. The primary exception to this normalization trend is in the signings of our Onsite and Fastenal Managed Inventory (FMI), which have yet to recover to pre-pandemic levels. To the extent that COVID-19 infections and/or interventions continue to meaningfully influence the marketplace, on a national, local, or business-specific basis, this can either directly impact or indirectly influence access to customer facilities and decision-makers, and lengthen the sales cycle for certain of our solutions.

However, it is possible the COVID-19 pandemic, particularly in light of variant strains of the virus, could further impact our operations and the operations of our suppliers and vendors as a result of quarantines, facility closures, illnesses, and travel and logistics restrictions. The extent to which the COVID-19 pandemic impacts our business, results of operations, and financial condition will depend on future developments, which are highly uncertain and cannot be predicted, including, but not limited to, the resumption of high levels of infection and hospitalization, the resulting impact on our customers, suppliers, and vendors, the remedial actions and stimulus measures adopted by federal, state, and local governments, and to what extent normal economic and operating conditions are impacted. We cannot reasonably estimate the future impact at this time.

additional share of common stock for every share of common stock they owned. The stock split took effect at the close of business on May 22, 2019. All historical common stock share and per share information for all periods presented in the accompanying consolidated financial statements and notes thereto have been retroactively adjusted to reflect the stock split.

The prior period balances for additional paid-in capital and common stock have been updated in both the Consolidated Balance Sheets and Consolidated Statements of Stockholders' Equity to reflect the impact of an immaterial correction which reclassified $2.9 from additional paid-in capital to common stock in connection with the 2019 stock split.

In March 2020, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) 2020-04, Reference Rate Reform (Topic 848): Facilitation of the Effects of Reference Rate Reform on Financial Reporting, which provides temporary optional expedients and exceptions to U.S. GAAP on contract modifications, hedging relationships, and other transactions affected by reference rate reform to ease entities' financial reporting burdens as the market transitions from the London Interbank Offered Rate (LIBOR) and other interbank offered rates to alternative reference rates. The guidance was effective upon issuance and may be applied prospectively to contract modifications made, hedging relationships entered into, and other transactions affected by reference rate reform, evaluated on or before December 31, 2022, beginning during the reporting period in which the guidance has been elected. We do not have any receivables, hedging relationships, or lease agreements that reference LIBOR or another reference rate expected to be discontinued. We are currently evaluating the impact of the new guidance on our consolidated financial statements; however, we have determined that, of our current debt commitments as outlined in detail in Note 9 'Debt Commitments', only the obligations described under Unsecured Revolving Credit Facility in Note 9 would be impacted by ASU 2020-04. Our Senior Unsecured Promissory Notes Payable described in Note 9 each have fixed interest rates.