Business Overview and Summary of Significant Accounting Policies	12 Months Ended
Dec. 31, 2015
Business Overview and Summary of Significant 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 operating a store-based business with approximately 2,600 locations. These locations are 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 and Accounts Receivable Net sales include products, services, and shipping and handling charges billed, net of any related sales incentives, and net of an estimate for product returns. We recognize revenue when persuasive evidence of an arrangement exists, title and risk of ownership have passed, the sales price is fixed or determinable, and collectibility is reasonably assured. These criteria are met at the time the product is shipped to or picked up by the customer. We recognize services at the time the service is completed and product is provided to the customer. We recognize revenue for shipping and handling charges billed at the time the products are shipped to or picked up by the customer. We estimate product returns based on historical return rates. Accounts receivable are stated at their estimated net realizable value. The allowance for doubtful accounts is based on an analysis of customer accounts and our historical experience with accounts receivable write-offs. Sales taxes (and value added taxes in foreign jurisdictions) collected from customers and remitted to governmental authorities are accounted for on a net basis and therefore are excluded from net sales. 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 period. The translation adjustments are deferred as a separate component of stockholders’ equity captioned accumulated other comprehensive (loss) income. Gains or losses resulting from transactions denominated in foreign currencies are included in 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. Financial Instruments and Marketable Securities All financial instruments are carried at amounts that approximate fair value. The fair value is the price at which an asset could be exchanged in a current transaction between knowledgeable, willing parties. Assets measured at fair value are categorized based upon the lowest level of significant input to the valuations. Level 1 inputs are quoted prices (unadjusted) in active markets for identical assets or liabilities. Level 2 inputs are quoted prices for similar assets and liabilities in active markets or inputs that are observable for the asset or liability, either directly or indirectly through market corroboration. Level 3 inputs are unobservable inputs based upon our own assumptions used to measure assets and liabilities at fair value. In determining fair value we use observable market data when available. Due to the varying short-term cash needs of our business, we periodically have available-for-sale marketable securities. We did not have any marketable securities as of December 31, 2015 or December 31, 2014. Available-for-sale securities are recorded at fair value based on current market value. Unrealized holding gains and losses on available-for-sale securities are excluded from earnings but are included in comprehensive income and are reported as a separate component of stockholders’ equity until realized, unless a decline in the market value of any available-for-sale security is below cost, then the amount is deemed other than temporary and is charged to net earnings, resulting in the establishment of a new cost basis for the security. Inventories Inventories, consisting of finished goods merchandise held for resale, are stated at the lower of cost (first in, first out method) or market. 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 lease space under operating leases for certain distribution centers, stores, and manufacturing locations. These leases do not have significant rent escalation holidays, concessions, leasehold improvement incentives, or other build-out clauses. Any such terms are recognized as rent expense over the term of the lease. Further, the leases do not contain contingent rent provisions. Leasehold improvements on operating leases are amortized over their estimated service lives on a straight-line basis, or the remaining lease term, whichever is shorter. We lease certain semi-tractors, pick-ups, and equipment under operating leases. Other Long-Lived Assets Other assets consist of prepaid deposits, goodwill, non-compete agreements, and other related 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 non-compete and related intangible assets are amortized on a straight-line basis over their estimated life. Accounting Estimates The preparation of the consolidated financial statements in conformity with U.S. generally accepted accounting principles (GAAP) requires us 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 consolidated financial statements and the reported amounts of revenues and expenses during the reported period. Actual results could differ from those estimates. Insurance Reserves We are self-insured for certain losses relating to medical, dental, workers’ compensation, and other casualty losses. Specific stop loss coverage is provided for catastrophic claims in order to limit exposure to significant claims. Losses and claims are charged to operations when it is probable a loss has been incurred and the amount can be reasonably estimated. Accrued insurance liabilities are based on claims filed but unpaid and estimates of claims incurred but not 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. We report the benefits of tax deductions in excess of recognized stock-based compensation as cash flows from financing activities, thereby reducing net cash flows from operating activities and increasing net cash flows from financing activities. 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 we meet the aggregation criteria outlined in the accounting standards as our various operations have similar (1) economic characteristics, (2) products and services, (3) customers, (4) distribution channels, and (5) regulatory environments. Therefore, we report as a single business segment.

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 operating a store-based business with approximately 2,600 locations. These locations are 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 and Accounts Receivable

Net sales include products, services, and shipping and handling charges billed, net of any related sales incentives, and net of an estimate for product returns. We recognize revenue when persuasive evidence of an arrangement exists, title and risk of ownership have passed, the sales price is fixed or determinable, and collectibility is reasonably assured. These criteria are met at the time the product is shipped to or picked up by the customer. We recognize services at the time the service is completed and product is provided to the customer. We recognize revenue for shipping and handling charges billed at the time the products are shipped to or picked up by the customer. We estimate product returns based on historical return rates. Accounts receivable are stated at their estimated net realizable value. The allowance for doubtful accounts is based on an analysis of customer accounts and our historical experience with accounts receivable write-offs. Sales taxes (and value added taxes in foreign jurisdictions) collected from customers and remitted to governmental authorities are accounted for on a net basis and therefore are excluded from net sales.

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 period. The translation adjustments are deferred as a separate component of stockholders’ equity captioned accumulated other comprehensive (loss) income. Gains or losses resulting from transactions denominated in foreign currencies are included in 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.

Financial Instruments and Marketable Securities

All financial instruments are carried at amounts that approximate fair value. The fair value is the price at which an asset could be exchanged in a current transaction between knowledgeable, willing parties. Assets measured at fair value are categorized based upon the lowest level of significant input to the valuations. Level 1 inputs are quoted prices (unadjusted) in active markets for identical assets or liabilities. Level 2 inputs are quoted prices for similar assets and liabilities in active markets or inputs that are observable for the asset or liability, either directly or indirectly through market corroboration. Level 3 inputs are unobservable inputs based upon our own assumptions used to measure assets and liabilities at fair value. In determining fair value we use observable market data when available.

Due to the varying short-term cash needs of our business, we periodically have available-for-sale marketable securities. We did not have any marketable securities as of December 31, 2015 or December 31, 2014. Available-for-sale securities are recorded at fair value based on current market value. Unrealized holding gains and losses on available-for-sale securities are excluded from earnings but are included in comprehensive income and are reported as a separate component of stockholders’ equity until realized, unless a decline in the market value of any available-for-sale security is below cost, then the amount is deemed other than temporary and is charged to net earnings, resulting in the establishment of a new cost basis for the security.

Inventories

Inventories, consisting of finished goods merchandise held for resale, are stated at the lower of cost (first in, first out method) or market.

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 lease space under operating leases for certain distribution centers, stores, and manufacturing locations. These leases do not have significant rent escalation holidays, concessions, leasehold improvement incentives, or other build-out clauses. Any such terms are recognized as rent expense over the term of the lease. Further, the leases do not contain contingent rent provisions. Leasehold improvements on operating leases are amortized over their estimated service lives on a straight-line basis, or the remaining lease term, whichever is shorter. We lease certain semi-tractors, pick-ups, and equipment under operating leases.

Other Long-Lived Assets

Other assets consist of prepaid deposits, goodwill, non-compete agreements, and other related 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 non-compete and related intangible assets are amortized on a straight-line basis over their estimated life.

Accounting Estimates

The preparation of the consolidated financial statements in conformity with U.S. generally accepted accounting principles (GAAP) requires us 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 consolidated financial statements and the reported amounts of revenues and expenses during the reported period. Actual results could differ from those estimates.

Insurance Reserves

We are self-insured for certain losses relating to medical, dental, workers’ compensation, and other casualty losses. Specific stop loss coverage is provided for catastrophic claims in order to limit exposure to significant claims. Losses and claims are charged to operations when it is probable a loss has been incurred and the amount can be reasonably estimated. Accrued insurance liabilities are based on claims filed but unpaid and estimates of claims incurred but not 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.

We report the benefits of tax deductions in excess of recognized stock-based compensation as cash flows from financing activities, thereby reducing net cash flows from operating activities and increasing net cash flows from financing activities.

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 we meet the aggregation criteria outlined in the accounting standards as our various operations have similar (1) economic characteristics, (2) products and services, (3) customers, (4) distribution channels, and (5) regulatory environments. Therefore, we report as a single business segment.