Fastenal (FAST) 10-K 5 Feb 18 2017 FY Annual report Financial data

Document And Entity Information

Document And Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2017	Jan. 19, 2018	Jun. 30, 2017
Document And Entity Information [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2017
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	FY
Entity Registrant Name	FASTENAL CO
Entity Central Index Key	815,556
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		287,603,912
Entity Public Float			$ 12,488,792,738
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Well-known Seasoned Issuer	Yes
Trading Symbol	fast

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 116.9	$ 112.7
Trade accounts receivable, net of allowance for doubtful accounts of $11.9 and $11.2, respectively	607.8	499.7
Inventories	1,092.9	993
Prepaid income taxes	0	12.9
Other current assets	118.1	102.5
Total current assets	1,935.7	1,720.8
Property and equipment, net	893.6	899.7
Other assets	81.2	48.4
Total assets	2,910.5	2,668.9
Current liabilities:
Current portion of debt	3	10.5
Accounts payable	147.5	108.8
Accrued expenses	194	156.4
Income taxes payable	6.5	0
Total current liabilities	351	275.7
Long-term debt	412	379.5
Deferred income tax liabilities	50.6	80.6
Commitments and contingencies (Notes 5, 9, 10, and 11)
Stockholders' equity:
Preferred stock: $0.01 par value, 5,000,000 shares authorized, no shares issued or outstanding	0	0
Common stock: $0.01 par value, 400,000,000 shares authorized, 287,591,536 and 289,161,924 shares issued and outstanding, respectively	2.9	2.9
Additional paid-in capital	8.5	37.4
Retained earnings	2,110.6	1,940.1
Accumulated other comprehensive loss	(25.1)	(47.3)
Total stockholders' equity	2,096.9	1,933.1
Total liabilities and stockholders' equity	$ 2,910.5	$ 2,668.9

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Current assets:
Trade accounts receivable, allowance for doubtful accounts	$ 11.9	$ 11.2
Preferred stock:
Par value (in dollars per share)	$ 0.01	$ 0.01
Authorized (in shares)	5,000,000	5,000,000
Issued (in shares)	0	0
Outstanding (in shares)	0	0
Common stock:
Par value (in dollars per share)	$ 0.01	$ 0.01
Authorized (in shares)	400,000,000	400,000,000
Issued (in shares)	287,591,536	289,161,924
Outstanding (in shares)	287,591,536	289,161,924

Consolidated Statements of Earn

Consolidated Statements of Earnings - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Statement [Abstract]
Net sales	$ 4,390.5	$ 3,962	$ 3,869.2
Cost of sales	2,226.9	1,997.2	1,920.3
Gross profit	2,163.6	1,964.8	1,948.9
Operating and administrative expenses	1,282.8	1,169.5	1,121.5
Gain on sale of property and equipment	(1)	(0.5)	(1.4)
Operating income	881.8	795.8	828.8
Interest income	0.4	0.4	0.4
Interest expense	(9.1)	(6.5)	(3.1)
Earnings before income taxes	873.1	789.7	826.1
Income tax expense	294.5	290.3	309.7
Net earnings	$ 578.6	$ 499.4	$ 516.4
Basic net earnings per share (in dollars per share)	$ 2.01	$ 1.73	$ 1.77
Diluted net earnings per share (in dollars per share)	$ 2.01	$ 1.73	$ 1.77
Basic weighted average shares outstanding (in shares)	288,208,435	288,949,525	291,453,107
Diluted weighted average shares outstanding (in shares)	288,342,733	289,157,523	292,045,442

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement of Comprehensive Income [Abstract]
Net earnings	$ 578.6	$ 499.4	$ 516.4
Other comprehensive income (loss), net of tax:
Foreign currency translation adjustments (net of tax of $0.0 in 2017, 2016, and 2015)	22.2	(0.9)	(38.6)
Comprehensive income	$ 600.8	$ 498.5	$ 477.8

Consolidated Statements of Com6

Consolidated Statements of Comprehensive Income (Parenthetical) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement of Comprehensive Income [Abstract]
Foreign currency translation adjustments, tax	$ 0	$ 0	$ 0

Consolidated Statements of Stoc

Consolidated Statements of Stockholders' Equity - USD ($) $ in Millions	Total	Common Stock [Member]	Additional Paid-In Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]
Balance at Dec. 31, 2014	$ 1,915.3	$ 3	$ 33.7	$ 1,886.4	$ (7.8)
Balance (in shares) at Dec. 31, 2014		295,900,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends paid in cash	(327.1)			(327.1)
Purchases of common stock	(292.9)	$ (0.1)	(60)	(232.8)
Purchases of common stock (in shares)		(7,100,000)
Stock options exercised	19.1	$ 0	19.1
Stock options exercised (in shares)		800,000
Stock-based compensation	5.8		5.8
Excess tax benefits from stock-based compensation	3.4		3.4
Net earnings	516.4			516.4
Other comprehensive income (loss)	(38.6)				(38.6)
Balance at Dec. 31, 2015	1,801.4	$ 2.9	2	1,842.9	(46.4)
Balance (in shares) at Dec. 31, 2015		289,600,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends paid in cash	(346.6)			(346.6)
Purchases of common stock	(59.5)	$ 0	(3.9)	(55.6)
Purchases of common stock (in shares)		(1,600,000)
Stock options exercised	29.3	$ 0	29.3
Stock options exercised (in shares)		1,200,000
Stock-based compensation	4.1		4.1
Excess tax benefits from stock-based compensation	5.9		5.9
Net earnings	499.4			499.4
Other comprehensive income (loss)	(0.9)				(0.9)
Balance at Dec. 31, 2016	$ 1,933.1	$ 2.9	37.4	1,940.1	(47.3)
Balance (in shares) at Dec. 31, 2016	289,161,924	289,200,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends paid in cash	$ (369.1)			(369.1)
Purchases of common stock	(82.6)	$ 0	(43.6)	(39)
Purchases of common stock (in shares)		(1,900,000)
Stock options exercised	9.5	$ 0	9.5
Stock options exercised (in shares)		300,000
Stock-based compensation	5.2		5.2
Net earnings	578.6			578.6
Other comprehensive income (loss)	22.2				22.2
Balance at Dec. 31, 2017	$ 2,096.9	$ 2.9	$ 8.5	$ 2,110.6	$ (25.1)
Balance (in shares) at Dec. 31, 2017	287,591,536	287,600,000

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Cash flows from operating activities:
Net earnings	$ 578.6	$ 499.4	$ 516.4
Adjustments to reconcile net earnings to net cash provided by operating activities, net of acquisitions:
Depreciation of property and equipment	123.6	103.5	86.1
Gain on sale of property and equipment	(1)	(0.5)	(1.4)
Bad debt expense	8.2	8.6	8.8
Deferred income taxes	(30)	25.6	8.3
Stock-based compensation	5.2	4.1	5.8
Amortization of intangible assets	3.8	0.5	0.5
Changes in operating assets and liabilities, net of acquisitions:
Trade accounts receivable	(103.7)	(40.5)	(20.6)
Inventories	(76.3)	(80.9)	(47.8)
Other current assets	(15.6)	29.1	(15.8)
Accounts payable	36.3	(17.2)	20.6
Accrued expenses	37.6	(28.6)	11.1
Income taxes	19.4	15.5	(26.6)
Other	(0.9)	1.3	4.9
Net cash provided by operating activities	585.2	519.9	550.3
Cash flows from investing activities:
Purchases of property and equipment	(119.9)	(189.5)	(155.2)
Proceeds from sale of property and equipment	7.4	6.5	9.9
Cash paid for acquisitions	(58.7)	0	(23.5)
Other	(8.1)	(5.1)	(11.8)
Net cash used in investing activities	(179.3)	(188.1)	(180.6)
Cash flows from financing activities:
Proceeds from debt obligations	1,015	950	1,215
Payments against debt obligations	(980)	(920)	(955)
Proceeds from exercise of stock options	9.5	29.3	19.1
Purchases of common stock	(82.6)	(59.5)	(292.9)
Payments of dividends	(369.1)	(346.6)	(327.1)
Net cash used in financing activities	(407.2)	(346.8)	(340.9)
Effect of exchange rate changes on cash and cash equivalents	5.5	(1.3)	(14.2)
Net increase (decrease) in cash and cash equivalents	4.2	(16.3)	14.6
Cash and cash equivalents at beginning of year	112.7	129	114.4
Cash and cash equivalents at end of year	116.9	112.7	129
Supplemental disclosure of cash flow information:
Cash paid for interest	8.7	6.2	3.1
Net cash paid for income taxes	$ 304.1	$ 248.3	$ 327

Business Overview and Summary o

Business Overview and Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2017
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 branch-based business (with an increasing number of Onsite locations). Collectively we refer to our branches and Onsite locations as in-market locations. We have approximately 3,000 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 and Accounts Receivable Net sales include products, services, shipping and handling charges, and lease fees 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 the product is provided to the customer. We recognize revenue for shipping and handling charges at the time the products are shipped to or picked up by the customer. We recognize revenue for lease fees on a straight-line basis over the corresponding lease term. 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 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 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, branches, 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, 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. 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, 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 operations 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. Considering the insignificance of our operations outside of North America, we report as a single business segment. Recently Adopted Accounting Pronouncements Effective January 1, 2017, we adopted the FASB ASU 2016-09, Improvements to Employee Share-Based Payment Accounting . The standard simplifies several aspects of the accounting for employee share-based payment transactions, including accounting for income taxes, forfeitures, and statutory withholding requirements, as well as classification in the Consolidated Statements of Cash Flows. As a result of the adoption, on a prospective basis, for the year ended December 31, 2017, we recognized $1.8 of excess tax benefits from stock-based compensation as a discrete item in our income tax expense. Historically, these amounts were recorded as additional paid-in capital. Upon adoption, we elected to apply the change retrospectively to our Consolidated Statements of Cash Flows for the years ended December 31, 2016 and December 31, 2015, which resulted in a reclassification of excess tax benefits from stock-based compensation of $5.9 and $3.4 , respectively, offsetting cash flows used in financing activities to cash flows provided by operating activities. We elected not to change our policy on accounting for forfeitures and will continue to estimate a requisite forfeiture rate. Additional amendments to the accounting for income taxes and minimum statutory withholding requirements had no impact on our results of operations. On December 22, 2017, the Securities and Exchange Commission ('SEC') staff issued Staff Accounting Bulletin No. 118 ('SAB 118') to address the application of U.S. GAAP related to the enactment of the comprehensive tax legislation, commonly referred to as the Tax Cut and Jobs Act (the 'Tax Act'). This guidance was adopted in the fourth quarter of 2017. Additional information regarding our adoption of this guidance is contained in Note 7. Recently Issued Accounting Pronouncements In August 2015, the FASB issued ASU 2015-14, Revenue from Contracts with Customers (Topic 606): Deferral of the Effective Date, which deferred the effective date of ASU 2014-09 for all entities by one year. This update is effective for public business entities for annual reporting periods beginning after December 15, 2017, including interim periods within those reporting periods. Earlier application was permitted only as of annual reporting periods beginning after December 15, 2016, including interim reporting periods within that reporting period. ASU 2014-09 was to become effective for us beginning January 2017; however, ASU 2015-14 deferred our effective date until January 2018, which is when we plan to adopt this standard. The ASU permits two methods of adoption: retrospectively to each prior reporting period presented (full retrospective method), or retrospectively with the cumulative effect of initially applying the guidance recognized at the date of initial application (the modified retrospective method). The ASU also requires expanded disclosures relating to the nature, amount, timing, and uncertainty of revenue and cash flows arising from contracts with customers. Additionally, qualitative and quantitative disclosures are required for customer contracts, significant judgments and changes in judgments, and assets recognized from the costs to obtain or fulfill a contract. We have completed the process of evaluating the effect of the adoption and determined there were no changes required to our reported revenues as a result of the adoption. The majority of our revenue arrangements generally consist of a single performance obligation to transfer promised goods or services. Based on our evaluation process and review of our contracts with customers, the timing and amount of revenue recognized based on ASU 2015-14 is consistent with our revenue recognition policy under previous guidance. We adopted the new standard effective January 1, 2018, using the modified retrospective approach, and will expand our consolidated financial statement disclosures in order to comply with the ASU. We have determined the adoption of ASU 2015-14 will not have a material impact on our results of operations, cash flows, or financial position. In February 2016, the FASB issued ASU 2016-02, Leases , which introduces the recognition of lease assets and lease liabilities by lessees for those leases classified as operating leases under previous guidance. The update is effective for annual reporting periods beginning after December 15, 2018, including interim periods within those reporting periods, with early adoption permitted. The guidance will be applied on a modified retrospective basis with the earliest period presented. Based on the effective date, this guidance will apply beginning January 2019, which is when we plan to adopt this ASU. While we are still in the process of evaluating the effect of adoption on our consolidated financial statements and are currently assessing our leases, we expect the adoption will lead to a material increase in the assets and liabilities recorded on our Consolidated Balance Sheets. As part of our assessment, we will need to determine the impact of lease extension provisions provided in our facility and vehicle leases which will impact the amount of the right of use asset and lease liability recorded under the ASU.

Acquisition

Acquisition	12 Months Ended
	Dec. 31, 2017
Business Combinations [Abstract]
Acquisition	Note 2. Acquisition On March 31, 2017, we acquired certain assets and assumed certain liabilities of Manufacturers Supply Company (‘Mansco’). Mansco, based in Hudsonville, Michigan, is a distributor of industrial and fastener supplies with a particularly strong market position with commercial furniture original equipment manufacturers. As such, this acquisition gives us a presence in a market where we have not meaningfully participated in the past, and provides Mansco with additional tools with which to service its customer base and reduce costs through economies of scale. The total purchase price for this acquisition, based on the acquisition date fair value, consisted of $57.9 paid in cash at closing, $0.8 paid in cash after closing pursuant to a post-closing purchase price adjustment, and a contingent consideration arrangement which requires us to pay the former owner up to a maximum of $2.5 (undiscounted) in cash after closing based on sales growth of the acquired business. We funded the purchase price for the acquisition with the proceeds from the issuance of a new series of senior unsecured promissory notes under our master note agreement in the aggregate principal amount of $60.0 . The fair value of the assets acquired and liabilities assumed as of the acquisition date is summarized below. Current assets $ 21.7 Property and equipment 0.9 Identifiable intangible assets 20.1 Current liabilities (1.8 ) Total identifiable net assets 40.9 Goodwill 18.4 Total fair value of assets acquired and liabilities assumed $ 59.3 The identifiable intangible assets consist mainly of the value of the customer relationships that were acquired and the goodwill consists largely of the synergies and economies of scale expected from combining the Mansco operations with our existing operations. The identifiable intangible assets and goodwill are deductible for income tax purposes. The amount of net sales and net earnings of the acquired business included in our Consolidated Statement of Earnings for the year ended December 31, 2017, and the pro forma net sales and net earnings of the combined entity had the acquisition occurred on January 1, 2016, are: 2017 2016 Net sales $ 53.5 49.6 Net earnings $ 5.5 4.9

Long-Lived Assets

Long-Lived Assets	12 Months Ended
	Dec. 31, 2017
Property, Plant and Equipment, Net, by Type [Abstract]
Long-Lived Assets	Note 3. Long-Lived Assets Property and equipment Property and equipment at year end consisted of the following: Depreciable Life in Years 2017 2016 Land — $ 38.2 37.3 Buildings and improvements 15 to 40 308.2 297.1 Automated distribution and warehouse equipment 5 to 30 220.0 216.3 Shelving, industrial vending, and equipment 3 to 10 812.9 723.9 Transportation equipment 3 to 5 76.3 71.7 Construction in progress — 149.3 152.5 1,604.9 1,498.8 Less accumulated depreciation (711.3 ) (599.1 ) Property and equipment, net $ 893.6 899.7

Accrued Expenses

Accrued Expenses	12 Months Ended
	Dec. 31, 2017
Payables and Accruals [Abstract]
Accrued Expenses	Note 4. Accrued Expenses Accrued expenses at year end consisted of the following: 2017 2016 Payroll and related taxes $ 26.0 23.2 Bonuses and commissions 19.8 14.2 Profit sharing contribution 10.6 8.7 Insurance reserves 39.0 34.6 Promotions 31.3 24.9 Indirect taxes 51.1 43.4 Other 16.2 7.4 Accrued expenses $ 194.0 156.4

Stockholders' Equity

Stockholders' Equity	12 Months Ended
	Dec. 31, 2017
Stockholders' Equity Note [Abstract]
Stockholders' Equity	Note 5. Stockholders' Equity Dividends On January 16, 2018 , our board of directors declared a quarterly dividend of $0.37 per share of common stock to be paid in cash on February 27, 2018 to shareholders of record at the close of business on January 31, 2018 . We paid aggregate annual dividends per share of $1.28 , $1.20 , and $1.12 in 2017 , 2016 , and 2015 , respectively. Stock Options Effective January 2, 2018, the compensation committee of our board of directors granted to our employees options to purchase a total of 520,601 shares of our common stock at an exercise strike price of $55.00 per share. The closing stock price on the effective date of the grant was $54.54 per share. On the same date, certain of our non-employee directors elected to forgo all or a portion of the 2018 annual cash retainer in exchange for options to acquire a total of 21,185 shares of our common stock at an exercise price of $55.00 per share. These options are subject to shareholder approval of the non-employee director stock option plan at our annual meeting of shareholders to be held in April 2018. The following tables summarize the details of options granted under our stock option plan that were still outstanding as of December 31, 2017, and the assumptions used to value those grants. All such grants were effective at the close of business on the date of grant. Options Granted Option Exercise (Strike) Price Closing Stock Price on Date of Grant December 31, 2017 Date of Grant Options Outstanding Options Exercisable January 3, 2017 764,789 $ 47.00 $ 46.95 713,097 — April 19, 2016 845,440 $ 46.00 $ 45.74 738,611 — April 21, 2015 893,220 $ 42.00 $ 41.26 674,499 142,072 April 22, 2014 955,000 $ 56.00 $ 50.53 567,500 158,750 April 16, 2013 205,000 $ 54.00 $ 49.25 101,750 55,250 April 17, 2012 1,235,000 $ 54.00 $ 49.01 952,001 772,977 April 19, 2011 410,000 $ 35.00 $ 31.78 60,350 35,350 April 20, 2010 530,000 $ 30.00 $ 27.13 79,550 54,550 April 21, 2009 790,000 $ 27.00 $ 17.61 61,550 61,550 Total 6,628,449 3,948,908 1,280,499 Date of Grant Risk-free Interest Rate Expected Life of Option in Years Expected Dividend Yield Expected Stock Volatility Estimated Fair Value of Stock Option January 3, 2017 1.9 % 5.00 2.6 % 24.49 % $ 8.40 April 19, 2016 1.3 % 5.00 2.6 % 26.34 % $ 8.18 April 21, 2015 1.3 % 5.00 2.7 % 26.84 % $ 7.35 April 22, 2014 1.8 % 5.00 2.0 % 28.55 % $ 9.57 April 16, 2013 0.7 % 5.00 1.6 % 37.42 % $ 12.66 April 17, 2012 0.9 % 5.00 1.4 % 39.25 % $ 13.69 April 19, 2011 2.1 % 5.00 1.6 % 39.33 % $ 11.20 April 20, 2010 2.6 % 5.00 1.5 % 39.10 % $ 8.14 April 21, 2009 1.9 % 5.00 1.0 % 38.80 % $ 3.64 All of the options in the tables above vest and become exercisable over a period of up to eight years. Generally, each option will terminate approximately nine years after the grant date. The fair value of each share-based option is estimated on the date of grant using a Black-Scholes valuation method that uses the assumptions listed above. The risk-free interest rate is based on the U.S. Treasury rate over the expected life of the option at the time of grant. The expected life is the average length of time over which we expect the employee groups will exercise their options, which is based on historical experience with similar grants. The dividend yield is estimated over the expected life of the option based on our current dividend payout, historical dividends paid, and expected future cash dividends. Expected stock volatilities are based on the movement of our stock price over the most recent historical period equivalent to the expected life of the option. A summary of activities under our stock option plan consisted of the following: Options Outstanding Exercise Price (1) Remaining Life (2) Outstanding as of January 1, 2017 3,757,947 $ 46.81 5.85 Granted 764,789 $ 47.00 9.00 Exercised (329,612 ) $ 28.59 Cancelled/forfeited (244,216 ) $ 48.22 Outstanding as of December 31, 2017 3,948,908 $ 48.28 5.89 Exercisable as of December 31, 2017 1,280,499 $ 50.07 3.78 Options Outstanding Exercise (1) Remaining Life (2) Outstanding as of January 1, 2016 4,530,982 $ 41.49 4.89 Granted 845,440 $ 46.00 8.41 Exercised (1,180,242 ) $ 24.80 Cancelled/forfeited (438,233 ) $ 49.49 Outstanding as of December 31, 2016 3,757,947 $ 46.81 5.85 Exercisable as of December 31, 2016 1,200,250 $ 45.93 3.74 (1) Weighted average exercise price. (2) Weighted average remaining contractual life in years. The total intrinsic value of stock options exercised during the years ended December 31, 2017 , 2016 , and 2015 was $6.9 , $23.2 , and $14.2 , respectively. The intrinsic value represents the difference between the exercise price and fair value of the underlying shares at the date of exercise. At December 31, 2017 , there was $14.6 of total unrecognized stock-based compensation expense related to outstanding unvested stock options granted under the plan. This expense is expected to be recognized over a weighted average period of 4.16 years. Any future change in estimated forfeitures will impact this amount. The total grant date fair value of stock options vested under our stock option plan during 2017 , 2016 , and 2015 was $4.2 , $7.1 , and $5.1 , respectively. Total stock-based compensation expense related to our stock option plan was $5.2 , $4.1 , and $5.8 for 2017 , 2016 , and 2015 , respectively. Earnings Per Share The following tables present a reconciliation of the denominators used in the computation of basic and diluted earnings per share and a summary of the options to purchase shares of common stock which were excluded from the diluted earnings calculation because they were anti-dilutive: Reconciliation 2017 2016 2015 Basic weighted average shares outstanding 288,208,435 288,949,525 291,453,107 Weighted shares assumed upon exercise of stock options 134,298 207,998 592,335 Diluted weighted average shares outstanding 288,342,733 289,157,523 292,045,442 Summary of Anti-dilutive Options Excluded 2017 2016 2015 Options to purchase shares of common stock 3,524,401 3,095,343 2,611,367 Weighted average exercise prices of options $ 49.85 50.09 51.89 Any dilutive impact summarized above related to periods when the average market price of our stock exceeded the exercise price of the potentially dilutive stock options then outstanding.

Retirement Savings Plan

Retirement Savings Plan	12 Months Ended
	Dec. 31, 2017
Defined Contribution Plan [Abstract]
Retirement Savings Plan	Note 6. Retirement Savings Plan The Fastenal Company and Subsidiaries 401(k) and Employee Stock Ownership Plan covers all of our employees in the United States. Our employees in Canada may participate in a Registered Retirement Savings Plan. The general purpose of both of these plans is to provide additional financial security during retirement by providing employees with an incentive to make regular savings contributions. In addition to the participation of our employees, we make annual profit sharing contributions based on an established formula. The expense recorded under this profit sharing formula was approximately $10.6 , $8.7 , and $13.7 for 2017 , 2016 , and 2015 , respectively.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Income Taxes	Note 7. Income Taxes Earnings before income taxes were derived from the following sources: 2017 2016 2015 Domestic $ 809.4 739.4 786.0 Foreign 63.7 50.3 40.1 Earnings before income taxes $ 873.1 789.7 826.1 Components of income tax expense (benefit) were as follows: 2017: Current Deferred Total Federal $ 270.6 (33.1 ) 237.5 State 33.2 3.3 36.5 Foreign 20.5 — 20.5 Income tax expense $ 324.3 (29.8 ) 294.5 2016: Current Deferred Total Federal $ 223.9 23.2 247.1 State 28.2 1.2 29.4 Foreign 12.6 1.2 13.8 Income tax expense $ 264.7 25.6 290.3 2015: Current Deferred Total Federal $ 256.7 7.4 264.1 State 31.3 0.2 31.5 Foreign 13.7 0.4 14.1 Income tax expense $ 301.7 8.0 309.7 Income tax expense in the accompanying consolidated financial statements differed from the expected expense as follows: 2017 2016 2015 Federal income tax expense at the 'expected' rate of 35% $ 305.6 276.4 289.1 Increase (decrease) attributed to: State income taxes, net of federal benefit 21.5 20.0 21.6 Transition tax 6.5 — — Effect of 2018 deferred rate change (30.8 ) — — Other, net (8.3 ) (6.1 ) (1.0 ) Total income tax expense $ 294.5 290.3 309.7 Effective income tax rate 33.7 % 36.8 % 37.5 % The tax effects of temporary differences that give rise to deferred income tax assets and liabilities at year end consisted of the following: 2017 2016 Deferred income tax assets (liabilities): Inventory costing and valuation methods $ 3.6 4.8 Allowance for doubtful accounts 3.0 4.3 Insurance reserves 8.4 11.5 Promotions payable 1.3 1.7 Stock-based compensation 5.2 6.8 Federal and state benefit of uncertain tax positions 0.9 1.9 Foreign net operating loss and credit carryforwards 4.2 5.1 Foreign valuation allowances (2.8 ) (4.0 ) Other, net 0.8 2.1 Total deferred income tax assets 24.6 34.2 Property and equipment (75.2 ) (114.8 ) Total deferred income tax liabilities (75.2 ) (114.8 ) Deferred income tax liabilities $ (50.6 ) (80.6 ) A reconciliation of the beginning and ending amount of total gross unrecognized tax benefits was as follows: 2017 2016 Balance at beginning of year: $ 5.4 5.4 Increase related to prior year tax positions 0.4 0.2 Decrease related to prior year tax positions (0.5 ) — Increase related to current year tax positions 0.7 0.8 Decrease related to statute of limitation lapses (1.1 ) (1.0 ) Settlements (0.5 ) — Balance at end of year: $ 4.4 5.4 Included in the liability for gross unrecognized tax benefits is an immaterial amount for interest and penalties, both of which we classify as a component of income tax expense. The amount of gross unrecognized tax benefits that would favorably impact the effective tax rate, if recognized, is not material. We do not anticipate significant changes in total unrecognized tax benefits during the next twelve months. Fastenal files income tax returns in the United States federal jurisdiction, all states, and various local and foreign jurisdictions. With limited exceptions, we are no longer subject to income tax examinations by taxing authorities for taxable years before 2015 in the case of United States federal examinations, and 2013 in the case of foreign, state, and local examinations. On December 22, 2017, the Tax Act was signed into law. The Tax Act makes broad and complex changes to the U.S. tax code that affected our income tax rate in 2017. The Tax Act reduces the U.S. federal corporate income tax rate from 35% to 21% and requires companies to pay a one-time transition tax on certain unrepatriated earnings from foreign subsidiaries that is payable over eight years. The Tax Act also establishes new tax laws that will affect 2018. ASC 740 requires a company to record the effects of a tax law change in the period of enactment, however, shortly after the enactment of the Tax Act, the SEC staff issued SAB 118, which allows a company to record a provisional amount when it does not have the necessary information available, prepared, or analyzed in reasonable detail to complete its accounting for the change in the tax law. The measurement period ends when the company has obtained, prepared and analyzed the information necessary to finalize its accounting, but cannot extend beyond one year. We have made a reasonable estimate of the impact of the Tax Act and recorded discrete items in our 2017 income tax expense of $24.4 which reflects an estimated reduction in our deferred income tax liabilities of $30.8 as a result of the maximum federal rate decrease to 21% from 35% which was partially offset by an estimated increase in income tax payable in the amount of $6.5 as a result of the transition tax on cash and cash equivalent balances related to accumulated earnings associated with our international operations. We are continuing to gather additional information related to estimates surrounding the remeasurement of deferred taxes and to unrepatriated earnings from foreign subsidiaries to more precisely compute the remeasurement of deferred taxes and the impact of the transition tax. In general, it is our practice and intention to permanently reinvest the earnings of our foreign subsidiaries and repatriate earnings only when the tax impact is zero or very minimal and that position has not changed following incurring the transition tax under the Tax Act. No deferred taxes have been provided for withholding taxes or other taxes that would result upon repatriation of our foreign investments to the United States. It is not practicable to estimate the amount of deferred income tax liabilities related to investments in these foreign subsidiaries.

Geographic Information

Geographic Information	12 Months Ended
	Dec. 31, 2017
Segments, Geographical Areas [Abstract]
Geographic Information	Note 8. Geographic Information Our revenues and long-lived assets related to the following geographic areas: Revenues 2017 2016 2015 United States $ 3,842.9 3,493.5 3,441.1 Canada 257.6 228.7 223.3 Other foreign countries 290.0 239.8 204.8 Total revenues $ 4,390.5 3,962.0 3,869.2 Long-Lived Assets 2017 2016 2015 United States $ 919.5 899.1 821.1 Canada 35.9 33.2 32.3 Other foreign countries 19.4 15.8 14.3 Total long-lived assets $ 974.8 948.1 867.7 The accounting policies of the operations in the various geographic areas are the same as those described in the summary of significant accounting policies. Long-lived assets consist of net property and equipment, deposits, goodwill, and other net intangibles. Revenues are attributed to countries based on the location of the branch from which the sale occurred. In each of the years presented in the table above, no single customer represented 5% or more of our consolidated net sales.

Operating Leases

Operating Leases	12 Months Ended
	Dec. 31, 2017
Leases, Operating [Abstract]
Operating Leases	Note 9. Operating Leases We lease space under non-cancelable operating leases for several distribution centers, several manufacturing locations, and certain branch 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. The net book value of leasehold improvements at December 31, 2017 was $2.5 . We lease certain semi-tractors and pick-ups under operating leases. Future minimum lease payments for all operating leases are as follows: Leased Facilities and Equipment Leased Vehicles Total 2018 $ 96.8 37.0 133.8 2019 70.9 23.7 94.6 2020 47.5 10.4 57.9 2021 25.2 1.9 27.1 2022 9.3 — 9.3 2023 and thereafter 2.0 — 2.0 Total minimum lease payments $ 251.7 73.0 324.7 Rent expense under all operating leases was as follows: Leased Facilities and Equipment Leased Vehicles Total 2017 $ 109.5 45.8 155.3 2016 $ 110.1 42.7 152.8 2015 $ 105.9 38.2 144.1 Certain operating leases for pick-up trucks contain residual value guarantee provisions which would generally become due at the expiration of the operating lease agreement if the fair value of the leased vehicles is less than the guaranteed residual value. The aggregate residual value guarantee related to these leases was approximately $75.5 . We believe the likelihood of funding the guarantee obligation under any provision of the operating lease agreements is remote other than where we have established an accrual for estimated losses, which was immaterial at December 31, 2017 . To the extent our fleet contains vehicles we estimate will settle at a gain, such gains on these vehicles will be recognized when we sell the vehicle.

Debt Commitments

Debt Commitments	12 Months Ended
	Dec. 31, 2017
Debt Disclosure [Abstract]
Debt Commitments	Note 10. Debt Commitments Credit Facility, Notes Payable, and Commitments Debt obligations and letters of credit outstanding at year end consisted of the following: 2017 2016 Outstanding loans under unsecured revolving credit facility $ 280.0 305.0 2.00% Senior unsecured promissory note payable 40.0 40.0 2.45% Senior unsecured promissory note payable 35.0 35.0 3.22% Senior unsecured promissory note payable 60.0 — Note payable under asset purchase agreement — 10.0 Total debt 415.0 390.0 Less: Current portion of debt (3.0 ) (10.5 ) Long-term debt $ 412.0 379.5 Outstanding letters of credit under unsecured revolving credit facility - contingent obligation $ 36.3 36.3 Unsecured Revolving Credit Facility We have a $700.0 committed unsecured revolving credit facility ('Credit Facility'). The Credit Facility includes a committed letter of credit subfacility of $55.0 . The commitments under the Credit Facility will expire (and any borrowings outstanding under the Credit Facility will become due and payable) on March 10, 2020 . In the next twelve months, we have the ability and intent to repay a portion of the outstanding loans using cash; therefore, we have classified this portion as a current liability. The Credit Facility contains certain financial and other covenants, and our right to borrow under the Credit Facility is conditioned upon, among other things, our compliance with these covenants. We are currently in compliance with these covenants. Borrowings under the Credit Facility generally bear interest at a rate per annum equal to the London Interbank Offered Rate ('LIBOR') for interest periods of various lengths selected by us, plus 0.95% . Based on the interest periods we have chosen, our weighted per annum interest rate at December 31, 2017 was approximately 2.5% . We pay a commitment fee for the unused portion of the Credit Facility. This fee is either 0.10% or 0.125% per annum based on our usage of the Credit Facility. Senior Unsecured Promissory Notes Payable On July 20, 2016 (the 'Effective Date'), we entered into a master note agreement (the 'Master Note Agreement') with certain institutional lenders, pursuant to which, during the period commencing on the Effective Date and ending three years thereafter, we may issue at our discretion in private placements, and the institutional lenders may purchase at their discretion, senior unsecured promissory notes of the company (the 'Notes') in the aggregate principal amount outstanding from time to time of up to $200.0 . The Notes will bear interest at either a fixed rate, or a floating rate based on LIBOR for an interest period of one , three , or six months . The Notes will mature no later than 12 years after the date of issuance thereof, in the case of fixed rate Notes, or 10 years after the date of issuance thereof, in the case of floating rate Notes. All of the Notes will be prepayable at our option in whole or in part. The Master Note Agreement contains certain financial and other covenants. We are currently in compliance with these covenants. Three series of Notes are currently outstanding under the Master Note Agreement. The first series of Notes ('Series A'), was issued on the Effective Date, is in an aggregate principal amount of $40.0 , is due and payable in full on July 20, 2021, and bears interest at a fixed rate of 2.00% per annum. The second series of Notes ('Series B'), was issued on the Effective Date, is in an aggregate principal amount of $35.0 , is due and payable in full on July 20, 2022, and bears interest at a fixed rate of 2.45% per annum. The third series of Notes ('Series C'), was issued on March 1, 2017, is in an aggregate principal amount of $60.0 , is due and payable in full on March 1, 2024, and bears interest at a fixed rate of 3.22% per annum. There is no amortization of these Notes prior to their maturity dates. Interest on such Notes is payable quarterly in arrears on January 20, April 20, July 20, and October 20 of each year. The carrying value of the Notes approximates fair value. The fair value was based on available external pricing data and current market rates for similar debt instruments, among other factors, which are classified as a level 2 measurement within the fair value hierarchy. Note Payable Under Asset Purchase Agreement On December 7, 2015, we signed an agreement to purchase, effective January 2, 2017 ('Asset Purchase Effective Date'), certain assets related to the collection and management of certain portions of our business and financial data from Apex Industrial Technologies, LLC ('Apex'), a provider of automated point-of-use dispensing and supply chain technologies. The agreement included a transition arrangement which required us to assume responsibility for certain software that was licensed by Apex. The total consideration for the assets was $27.0 , of which $12.0 was paid in cash in December 2015 in advance of the Asset Purchase Effective Date. The remaining $15.0 was payable in installments pursuant to an unsecured note. The first $5.0 installment was paid in December 2016, the second $5.0 was paid in June 2017, and the final installment of $5.0 was paid in December 2017. Interest on the unpaid principal balance of the note was due and payable on the last day of each calendar quarter at an annual rate of 0.56% . In 2015, the $15.0 note represented a non-cash investing and financing activity in our Consolidated Statements of Cash Flows, while the payments made in 2017, 2016, and 2015 are included in our Consolidated Statements of Cash Flows as net cash used in investing activities in 'Other'.

Legal Contingencies

Legal Contingencies	12 Months Ended
	Dec. 31, 2017
Commitments and Contingencies Disclosure [Abstract]
Legal Contingencies	Note 11. Legal Contingencies We are involved in certain legal actions. The outcomes of these legal actions are not within our complete control and may not be known for prolonged periods of time. In some actions, the claimants seek damages, as well as other relief, that could require significant expenditures or result in lost revenues. We record a liability for these legal actions when a loss is known or considered probable and the amount can be reasonably estimated. If the reasonable estimate of a known or probable loss is a range, and no amount within the range is a better estimate than any other, the minimum amount of the range is accrued. If a loss is reasonably possible but not known or probable, and can be reasonably estimated, the estimated loss or range of loss is disclosed. In most cases, significant judgment is required to estimate the amount and timing of a loss to be recorded. As of December 31, 2017 , there were no litigation matters that we consider to be probable or reasonably possible to have a material adverse outcome.

Sales by Product Line

Sales by Product Line	12 Months Ended
	Dec. 31, 2017
Sales by Product Line [Abstract]
Sales by Product Line	Note 12. Sales by Product Line The percentages of our sales by product line were as follows: Type Introduced 2017 2016 2015 Fasteners (1) 1967 35.6% 36.6% 38.3% Tools 1993 10.1% 9.9% 9.5% Cutting tools 1996 5.8% 5.7% 5.6% Hydraulics & pneumatics 1996 6.8% 6.9% 7.2% Material handling 1996 6.3% 6.4% 6.5% Janitorial supplies 1996 7.6% 7.6% 7.5% Electrical supplies 1997 4.9% 4.8% 4.7% Welding supplies 1997 4.6% 4.6% 4.7% Safety supplies (2) 1999 15.2% 14.9% 13.9% Metals 2001 0.5% 0.5% 0.5% Direct ship (3) 2004 0.5% 0.5% 0.4% Office supplies 2010 0.1% 0.1% 0.1% Other 2.0% 1.5% 1.1% 100.0% 100.0% 100.0% (1) Fastener product line represents fasteners and miscellaneous supplies. (2) The safety supplies product line has expanded, as a percentage of sales, in the last several years due to our industrial vending program. (3) Direct ship represents a cross section of products from the remaining product lines. The items included here represent certain items with historically low gross profit margins which are shipped directly from our distribution channel to our customers, bypassing our branch network.

Subsequent Events

Subsequent Events	12 Months Ended
	Dec. 31, 2017
Subsequent Events [Abstract]
Subsequent Events	Note 13. Subsequent Events We evaluated all subsequent event activity and concluded that no subsequent events have occurred that would require recognition in the consolidated financial statements or disclosure in the Notes to Consolidated Financial Statements, with the exception of the dividend declaration and stock option activities disclosed in Note 5.

Selected Quarterly Financial Da

Selected Quarterly Financial Data (Unaudited)	12 Months Ended
	Dec. 31, 2017
Selected Quarterly Financial Information [Abstract]
Selected Quarterly Financial Data (Unaudited)	Note 14. Selected Quarterly Financial Data (Unaudited) (Amounts in millions except per share information) 2017: Net Sales Gross Profit Pre-tax Earnings Net Earnings Basic Net (1) Diluted Net Earnings per Share (1) First quarter $ 1,047.7 518.0 210.9 134.2 0.46 0.46 Second quarter 1,121.5 558.5 235.4 148.9 0.52 0.52 Third quarter 1,132.8 555.9 226.0 143.1 0.50 0.50 Fourth quarter 1,088.5 531.2 200.8 152.4 (2) 0.53 (2) 0.53 (2) Total $ 4,390.5 2,163.6 873.1 578.6 (3) 2.01 (3) 2.01 (3) 2016: Net Sales Gross Profit Pre-tax Earnings Net Earnings Basic Net (1) Diluted Net Earnings per Share (1) First quarter $ 986.7 491.5 199.9 126.2 0.44 0.44 Second quarter 1,014.3 501.6 207.8 131.5 0.46 0.45 Third quarter 1,013.1 499.8 201.2 126.9 0.44 0.44 Fourth quarter 947.9 471.9 180.8 114.8 0.40 0.40 Total $ 3,962.0 1,964.8 789.7 499.4 1.73 1.73 (1) Amounts may not foot due to rounding difference. (2) Absent the impact of the Tax Act, our net earnings for the fourth quarter of 2017 would have been approximately $128.1 , and our basic and diluted net earnings per share would have each been $0.45 . (3) Absent the impact of the Tax Act, our net earnings for 2017 would have been approximately $554.2 , and our basic and diluted net earnings per share would have each been $1.92 .

Schedule II-Valuation and Quali

Schedule II-Valuation and Qualifying Accounts	12 Months Ended
	Dec. 31, 2017
Valuation and Qualifying Accounts [Abstract]
Schedule II-Valuation and Qualifying Accounts	Schedule II—Valuation and Qualifying Accounts Years ended December 31, 2017 , 2016 , and 2015 (Amounts in millions) Description Balance at Beginning of Year "Additions" Charged to Costs and Expenses "Other" Additions (Deductions) "Less" Deductions Balance at End of Year Year ended December 31, 2017 Allowance for doubtful accounts $ 11.2 8.2 — 7.5 11.9 Insurance reserves $ 34.6 68.2 (1) — 63.8 (2) 39.0 Year ended December 31, 2016 Allowance for doubtful accounts $ 11.7 8.5 — 9.0 11.2 Insurance reserves $ 31.8 62.3 (1) — 59.5 (2) 34.6 Year ended December 31, 2015 Allowance for doubtful accounts $ 12.6 8.8 — 9.7 11.7 Insurance reserves $ 31.1 54.3 (1) — 53.6 (2) 31.8 (1) Includes costs and expenses incurred for premiums and claims related to health and general insurance. (2) Includes costs and expenses paid for premiums and claims related to health and general insurance. See accompanying Report of Independent Registered Public Accounting Firm incorporated herein by reference.

Business Overview and Summary24

Business Overview and Summary of Significant Accounting Policies (Policy)	12 Months Ended
	Dec. 31, 2017
Accounting Policies [Abstract]
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, shipping and handling charges, and lease fees 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 the product is provided to the customer. We recognize revenue for shipping and handling charges at the time the products are shipped to or picked up by the customer. We recognize revenue for lease fees on a straight-line basis over the corresponding lease term. 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 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 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.
Leases	We lease space under operating leases for certain distribution centers, branches, 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, 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.
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, 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 operations 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. Considering the insignificance of our operations outside of North America, we report as a single business segment.
Recently Adopted and Recently Issued Accounting Pronouncements	Recently Adopted Accounting Pronouncements Effective January 1, 2017, we adopted the FASB ASU 2016-09, Improvements to Employee Share-Based Payment Accounting . The standard simplifies several aspects of the accounting for employee share-based payment transactions, including accounting for income taxes, forfeitures, and statutory withholding requirements, as well as classification in the Consolidated Statements of Cash Flows. As a result of the adoption, on a prospective basis, for the year ended December 31, 2017, we recognized $1.8 of excess tax benefits from stock-based compensation as a discrete item in our income tax expense. Historically, these amounts were recorded as additional paid-in capital. Upon adoption, we elected to apply the change retrospectively to our Consolidated Statements of Cash Flows for the years ended December 31, 2016 and December 31, 2015, which resulted in a reclassification of excess tax benefits from stock-based compensation of $5.9 and $3.4 , respectively, offsetting cash flows used in financing activities to cash flows provided by operating activities. We elected not to change our policy on accounting for forfeitures and will continue to estimate a requisite forfeiture rate. Additional amendments to the accounting for income taxes and minimum statutory withholding requirements had no impact on our results of operations. On December 22, 2017, the Securities and Exchange Commission ('SEC') staff issued Staff Accounting Bulletin No. 118 ('SAB 118') to address the application of U.S. GAAP related to the enactment of the comprehensive tax legislation, commonly referred to as the Tax Cut and Jobs Act (the 'Tax Act'). This guidance was adopted in the fourth quarter of 2017. Additional information regarding our adoption of this guidance is contained in Note 7. Recently Issued Accounting Pronouncements In August 2015, the FASB issued ASU 2015-14, Revenue from Contracts with Customers (Topic 606): Deferral of the Effective Date, which deferred the effective date of ASU 2014-09 for all entities by one year. This update is effective for public business entities for annual reporting periods beginning after December 15, 2017, including interim periods within those reporting periods. Earlier application was permitted only as of annual reporting periods beginning after December 15, 2016, including interim reporting periods within that reporting period. ASU 2014-09 was to become effective for us beginning January 2017; however, ASU 2015-14 deferred our effective date until January 2018, which is when we plan to adopt this standard. The ASU permits two methods of adoption: retrospectively to each prior reporting period presented (full retrospective method), or retrospectively with the cumulative effect of initially applying the guidance recognized at the date of initial application (the modified retrospective method). The ASU also requires expanded disclosures relating to the nature, amount, timing, and uncertainty of revenue and cash flows arising from contracts with customers. Additionally, qualitative and quantitative disclosures are required for customer contracts, significant judgments and changes in judgments, and assets recognized from the costs to obtain or fulfill a contract. We have completed the process of evaluating the effect of the adoption and determined there were no changes required to our reported revenues as a result of the adoption. The majority of our revenue arrangements generally consist of a single performance obligation to transfer promised goods or services. Based on our evaluation process and review of our contracts with customers, the timing and amount of revenue recognized based on ASU 2015-14 is consistent with our revenue recognition policy under previous guidance. We adopted the new standard effective January 1, 2018, using the modified retrospective approach, and will expand our consolidated financial statement disclosures in order to comply with the ASU. We have determined the adoption of ASU 2015-14 will not have a material impact on our results of operations, cash flows, or financial position. In February 2016, the FASB issued ASU 2016-02, Leases , which introduces the recognition of lease assets and lease liabilities by lessees for those leases classified as operating leases under previous guidance. The update is effective for annual reporting periods beginning after December 15, 2018, including interim periods within those reporting periods, with early adoption permitted. The guidance will be applied on a modified retrospective basis with the earliest period presented. Based on the effective date, this guidance will apply beginning January 2019, which is when we plan to adopt this ASU. While we are still in the process of evaluating the effect of adoption on our consolidated financial statements and are currently assessing our leases, we expect the adoption will lead to a material increase in the assets and liabilities recorded on our Consolidated Balance Sheets. As part of our assessment, we will need to determine the impact of lease extension provisions provided in our facility and vehicle leases which will impact the amount of the right of use asset and lease liability recorded under the ASU.

Acquisition (Tables)

Acquisition (Tables)	12 Months Ended
	Dec. 31, 2017
Business Combinations [Abstract]
Schedule of Fair Value Allocation for Assets Acquired and Liabilities Assumed	The fair value of the assets acquired and liabilities assumed as of the acquisition date is summarized below. Current assets $ 21.7 Property and equipment 0.9 Identifiable intangible assets 20.1 Current liabilities (1.8 ) Total identifiable net assets 40.9 Goodwill 18.4 Total fair value of assets acquired and liabilities assumed $ 59.3
Business Acquisition, Pro Forma Information	The amount of net sales and net earnings of the acquired business included in our Consolidated Statement of Earnings for the year ended December 31, 2017, and the pro forma net sales and net earnings of the combined entity had the acquisition occurred on January 1, 2016, are: 2017 2016 Net sales $ 53.5 49.6 Net earnings $ 5.5 4.9

Long-Lived Assets (Tables)

Long-Lived Assets (Tables)	12 Months Ended
	Dec. 31, 2017
Property, Plant and Equipment, Net, by Type [Abstract]
Schedule of Property and Equipment	Property and equipment at year end consisted of the following: Depreciable Life in Years 2017 2016 Land — $ 38.2 37.3 Buildings and improvements 15 to 40 308.2 297.1 Automated distribution and warehouse equipment 5 to 30 220.0 216.3 Shelving, industrial vending, and equipment 3 to 10 812.9 723.9 Transportation equipment 3 to 5 76.3 71.7 Construction in progress — 149.3 152.5 1,604.9 1,498.8 Less accumulated depreciation (711.3 ) (599.1 ) Property and equipment, net $ 893.6 899.7

Accrued Expenses (Tables)

Accrued Expenses (Tables)	12 Months Ended
	Dec. 31, 2017
Payables and Accruals [Abstract]
Schedule of Accrued Expenses	Accrued expenses at year end consisted of the following: 2017 2016 Payroll and related taxes $ 26.0 23.2 Bonuses and commissions 19.8 14.2 Profit sharing contribution 10.6 8.7 Insurance reserves 39.0 34.6 Promotions 31.3 24.9 Indirect taxes 51.1 43.4 Other 16.2 7.4 Accrued expenses $ 194.0 156.4

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	12 Months Ended
	Dec. 31, 2017
Stockholders' Equity Note [Abstract]
Stock Option Plan Activity and Stock Options Granted	A summary of activities under our stock option plan consisted of the following: Options Outstanding Exercise Price (1) Remaining Life (2) Outstanding as of January 1, 2017 3,757,947 $ 46.81 5.85 Granted 764,789 $ 47.00 9.00 Exercised (329,612 ) $ 28.59 Cancelled/forfeited (244,216 ) $ 48.22 Outstanding as of December 31, 2017 3,948,908 $ 48.28 5.89 Exercisable as of December 31, 2017 1,280,499 $ 50.07 3.78 Options Outstanding Exercise (1) Remaining Life (2) Outstanding as of January 1, 2016 4,530,982 $ 41.49 4.89 Granted 845,440 $ 46.00 8.41 Exercised (1,180,242 ) $ 24.80 Cancelled/forfeited (438,233 ) $ 49.49 Outstanding as of December 31, 2016 3,757,947 $ 46.81 5.85 Exercisable as of December 31, 2016 1,200,250 $ 45.93 3.74 (1) Weighted average exercise price. (2) Weighted average remaining contractual life in years. The following tables summarize the details of options granted under our stock option plan that were still outstanding as of December 31, 2017, and the assumptions used to value those grants. All such grants were effective at the close of business on the date of grant. Options Granted Option Exercise (Strike) Price Closing Stock Price on Date of Grant December 31, 2017 Date of Grant Options Outstanding Options Exercisable January 3, 2017 764,789 $ 47.00 $ 46.95 713,097 — April 19, 2016 845,440 $ 46.00 $ 45.74 738,611 — April 21, 2015 893,220 $ 42.00 $ 41.26 674,499 142,072 April 22, 2014 955,000 $ 56.00 $ 50.53 567,500 158,750 April 16, 2013 205,000 $ 54.00 $ 49.25 101,750 55,250 April 17, 2012 1,235,000 $ 54.00 $ 49.01 952,001 772,977 April 19, 2011 410,000 $ 35.00 $ 31.78 60,350 35,350 April 20, 2010 530,000 $ 30.00 $ 27.13 79,550 54,550 April 21, 2009 790,000 $ 27.00 $ 17.61 61,550 61,550 Total 6,628,449 3,948,908 1,280,499
Fair Value Assumptions for Options Granted	Date of Grant Risk-free Interest Rate Expected Life of Option in Years Expected Dividend Yield Expected Stock Volatility Estimated Fair Value of Stock Option January 3, 2017 1.9 % 5.00 2.6 % 24.49 % $ 8.40 April 19, 2016 1.3 % 5.00 2.6 % 26.34 % $ 8.18 April 21, 2015 1.3 % 5.00 2.7 % 26.84 % $ 7.35 April 22, 2014 1.8 % 5.00 2.0 % 28.55 % $ 9.57 April 16, 2013 0.7 % 5.00 1.6 % 37.42 % $ 12.66 April 17, 2012 0.9 % 5.00 1.4 % 39.25 % $ 13.69 April 19, 2011 2.1 % 5.00 1.6 % 39.33 % $ 11.20 April 20, 2010 2.6 % 5.00 1.5 % 39.10 % $ 8.14 April 21, 2009 1.9 % 5.00 1.0 % 38.80 % $ 3.64
Reconciliation of Denominators used in Computation of Basic and Diluted Earnings per Share	The following tables present a reconciliation of the denominators used in the computation of basic and diluted earnings per share and a summary of the options to purchase shares of common stock which were excluded from the diluted earnings calculation because they were anti-dilutive: Reconciliation 2017 2016 2015 Basic weighted average shares outstanding 288,208,435 288,949,525 291,453,107 Weighted shares assumed upon exercise of stock options 134,298 207,998 592,335 Diluted weighted average shares outstanding 288,342,733 289,157,523 292,045,442
Anti-Dilutive Options Excluded	Summary of Anti-dilutive Options Excluded 2017 2016 2015 Options to purchase shares of common stock 3,524,401 3,095,343 2,611,367 Weighted average exercise prices of options $ 49.85 50.09 51.89

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Earnings Before Income Taxes	Earnings before income taxes were derived from the following sources: 2017 2016 2015 Domestic $ 809.4 739.4 786.0 Foreign 63.7 50.3 40.1 Earnings before income taxes $ 873.1 789.7 826.1
Components of Income Tax Expense (Benefit)	Components of income tax expense (benefit) were as follows: 2017: Current Deferred Total Federal $ 270.6 (33.1 ) 237.5 State 33.2 3.3 36.5 Foreign 20.5 — 20.5 Income tax expense $ 324.3 (29.8 ) 294.5 2016: Current Deferred Total Federal $ 223.9 23.2 247.1 State 28.2 1.2 29.4 Foreign 12.6 1.2 13.8 Income tax expense $ 264.7 25.6 290.3 2015: Current Deferred Total Federal $ 256.7 7.4 264.1 State 31.3 0.2 31.5 Foreign 13.7 0.4 14.1 Income tax expense $ 301.7 8.0 309.7
Difference In Income Tax Expense And Expected Expense	Income tax expense in the accompanying consolidated financial statements differed from the expected expense as follows: 2017 2016 2015 Federal income tax expense at the 'expected' rate of 35% $ 305.6 276.4 289.1 Increase (decrease) attributed to: State income taxes, net of federal benefit 21.5 20.0 21.6 Transition tax 6.5 — — Effect of 2018 deferred rate change (30.8 ) — — Other, net (8.3 ) (6.1 ) (1.0 ) Total income tax expense $ 294.5 290.3 309.7 Effective income tax rate 33.7 % 36.8 % 37.5 %
Summary of Temporary Differences That Give Rise to Deferred Income Tax Assets And Liabilities	The tax effects of temporary differences that give rise to deferred income tax assets and liabilities at year end consisted of the following: 2017 2016 Deferred income tax assets (liabilities): Inventory costing and valuation methods $ 3.6 4.8 Allowance for doubtful accounts 3.0 4.3 Insurance reserves 8.4 11.5 Promotions payable 1.3 1.7 Stock-based compensation 5.2 6.8 Federal and state benefit of uncertain tax positions 0.9 1.9 Foreign net operating loss and credit carryforwards 4.2 5.1 Foreign valuation allowances (2.8 ) (4.0 ) Other, net 0.8 2.1 Total deferred income tax assets 24.6 34.2 Property and equipment (75.2 ) (114.8 ) Total deferred income tax liabilities (75.2 ) (114.8 ) Deferred income tax liabilities $ (50.6 ) (80.6 )
Reconciliation of The Beginning and Ending Amount of Total Gross Unrecognized Tax Benefits	A reconciliation of the beginning and ending amount of total gross unrecognized tax benefits was as follows: 2017 2016 Balance at beginning of year: $ 5.4 5.4 Increase related to prior year tax positions 0.4 0.2 Decrease related to prior year tax positions (0.5 ) — Increase related to current year tax positions 0.7 0.8 Decrease related to statute of limitation lapses (1.1 ) (1.0 ) Settlements (0.5 ) — Balance at end of year: $ 4.4 5.4

Geographic Information (Tables)

Geographic Information (Tables)	12 Months Ended
	Dec. 31, 2017
Segments, Geographical Areas [Abstract]
Revenues and Long-Lived Assets By Geographic Areas	Our revenues and long-lived assets related to the following geographic areas: Revenues 2017 2016 2015 United States $ 3,842.9 3,493.5 3,441.1 Canada 257.6 228.7 223.3 Other foreign countries 290.0 239.8 204.8 Total revenues $ 4,390.5 3,962.0 3,869.2 Long-Lived Assets 2017 2016 2015 United States $ 919.5 899.1 821.1 Canada 35.9 33.2 32.3 Other foreign countries 19.4 15.8 14.3 Total long-lived assets $ 974.8 948.1 867.7

Operating Leases (Tables)

Operating Leases (Tables)	12 Months Ended
	Dec. 31, 2017
Leases, Operating [Abstract]
Future Minimum Lease Payments	Future minimum lease payments for all operating leases are as follows: Leased Facilities and Equipment Leased Vehicles Total 2018 $ 96.8 37.0 133.8 2019 70.9 23.7 94.6 2020 47.5 10.4 57.9 2021 25.2 1.9 27.1 2022 9.3 — 9.3 2023 and thereafter 2.0 — 2.0 Total minimum lease payments $ 251.7 73.0 324.7
Rent Expense	Rent expense under all operating leases was as follows: Leased Facilities and Equipment Leased Vehicles Total 2017 $ 109.5 45.8 155.3 2016 $ 110.1 42.7 152.8 2015 $ 105.9 38.2 144.1

Debt Commitments (Tables)

Debt Commitments (Tables)	12 Months Ended
	Dec. 31, 2017
Debt Disclosure [Abstract]
Schedule of Debt Obligations and Letters of Credit Outstanding	Debt obligations and letters of credit outstanding at year end consisted of the following: 2017 2016 Outstanding loans under unsecured revolving credit facility $ 280.0 305.0 2.00% Senior unsecured promissory note payable 40.0 40.0 2.45% Senior unsecured promissory note payable 35.0 35.0 3.22% Senior unsecured promissory note payable 60.0 — Note payable under asset purchase agreement — 10.0 Total debt 415.0 390.0 Less: Current portion of debt (3.0 ) (10.5 ) Long-term debt $ 412.0 379.5 Outstanding letters of credit under unsecured revolving credit facility - contingent obligation $ 36.3 36.3

Sales by Product Line (Tables)

Sales by Product Line (Tables)	12 Months Ended
	Dec. 31, 2017
Sales by Product Line [Abstract]
Percentages Of Sales By Product Line	The percentages of our sales by product line were as follows: Type Introduced 2017 2016 2015 Fasteners (1) 1967 35.6% 36.6% 38.3% Tools 1993 10.1% 9.9% 9.5% Cutting tools 1996 5.8% 5.7% 5.6% Hydraulics & pneumatics 1996 6.8% 6.9% 7.2% Material handling 1996 6.3% 6.4% 6.5% Janitorial supplies 1996 7.6% 7.6% 7.5% Electrical supplies 1997 4.9% 4.8% 4.7% Welding supplies 1997 4.6% 4.6% 4.7% Safety supplies (2) 1999 15.2% 14.9% 13.9% Metals 2001 0.5% 0.5% 0.5% Direct ship (3) 2004 0.5% 0.5% 0.4% Office supplies 2010 0.1% 0.1% 0.1% Other 2.0% 1.5% 1.1% 100.0% 100.0% 100.0% (1) Fastener product line represents fasteners and miscellaneous supplies. (2) The safety supplies product line has expanded, as a percentage of sales, in the last several years due to our industrial vending program. (3) Direct ship represents a cross section of products from the remaining product lines. The items included here represent certain items with historically low gross profit margins which are shipped directly from our distribution channel to our customers, bypassing our branch network.

Selected Quarterly Financial 34

Selected Quarterly Financial Data (Unaudited) (Tables)	12 Months Ended
	Dec. 31, 2017
Selected Quarterly Financial Information [Abstract]
Schedule of Quarterly Financial Information	(Amounts in millions except per share information) 2017: Net Sales Gross Profit Pre-tax Earnings Net Earnings Basic Net (1) Diluted Net Earnings per Share (1) First quarter $ 1,047.7 518.0 210.9 134.2 0.46 0.46 Second quarter 1,121.5 558.5 235.4 148.9 0.52 0.52 Third quarter 1,132.8 555.9 226.0 143.1 0.50 0.50 Fourth quarter 1,088.5 531.2 200.8 152.4 (2) 0.53 (2) 0.53 (2) Total $ 4,390.5 2,163.6 873.1 578.6 (3) 2.01 (3) 2.01 (3) 2016: Net Sales Gross Profit Pre-tax Earnings Net Earnings Basic Net (1) Diluted Net Earnings per Share (1) First quarter $ 986.7 491.5 199.9 126.2 0.44 0.44 Second quarter 1,014.3 501.6 207.8 131.5 0.46 0.45 Third quarter 1,013.1 499.8 201.2 126.9 0.44 0.44 Fourth quarter 947.9 471.9 180.8 114.8 0.40 0.40 Total $ 3,962.0 1,964.8 789.7 499.4 1.73 1.73 (1) Amounts may not foot due to rounding difference. (2) Absent the impact of the Tax Act, our net earnings for the fourth quarter of 2017 would have been approximately $128.1 , and our basic and diluted net earnings per share would have each been $0.45 . (3) Absent the impact of the Tax Act, our net earnings for 2017 would have been approximately $554.2 , and our basic and diluted net earnings per share would have each been $1.92 .

Business Overview and Summary35

Business Overview and Summary of Significant Accounting Policies - Additional Information (Details) location in Thousands	12 Months Ended
	Dec. 31, 2017USD ($)location	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)
Accounting Policies [Abstract]
Approximate number of in-market locations | location	3
Impairment of property and equipment long-lived assets	$ 0	$ 0	$ 0
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Excess tax benefits from stock-based compensation	1,800,000
Reclassification offsetting cash flows used in financing activities	407,200,000	346,800,000	340,900,000
Reclassification to cash flows provided by operating activities	$ 585,200,000	519,900,000	550,300,000
Accounting Standards Update 2016-09 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Reclassification offsetting cash flows used in financing activities		5,900,000	3,400,000
Reclassification to cash flows provided by operating activities		$ 5,900,000	$ 3,400,000

Acquisition - Additional Inform

Acquisition - Additional Information (Details) - USD ($)	Mar. 31, 2017	Dec. 31, 2017
Senior Unsecured Promissory Notes [Member] | 3.22% Senior Unsecured Promissory Note Payable [Member]
Business Acquisition [Line Items]
Debt issuance, aggregate principal amount	$ 60,000,000	$ 60,000,000
Manufacturers Supply Company [Member]
Business Acquisition [Line Items]
Purchase price paid in cash at closing	$ 57,900,000
Purchase price paid in cash after closing		800,000
Maximum contingent consideration arrangement		$ 2,500,000

Acquisition - Fair Value Alloca

Acquisition - Fair Value Allocation for Assets Acquired and Liabilities Assumed (Details) - Manufacturers Supply Company [Member] $ in Millions	Mar. 31, 2017USD ($)
Business Acquisition [Line Items]
Current assets	$ 21.7
Property and equipment	0.9
Identifiable intangible assets	20.1
Current liabilities	(1.8)
Total identifiable net assets	40.9
Goodwill	18.4
Total fair value of assets acquired and liabilities assumed	$ 59.3

Acquisition - Pro Forma Informa

Acquisition - Pro Forma Information (Details) - Manufacturers Supply Company [Member] - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Business Acquisition [Line Items]
Net sales	$ 53.5	$ 49.6
Net earnings	$ 5.5	$ 4.9

Long-Lived Assets (Details)

Long-Lived Assets (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Property and Equipment, Net [Line Items]
Property and equipment	$ 1,604.9	$ 1,498.8
Less accumulated depreciation	(711.3)	(599.1)
Property and equipment, net	893.6	899.7
Land [Member]
Property and Equipment, Net [Line Items]
Property and equipment	38.2	37.3
Buildings and improvements [Member]
Property and Equipment, Net [Line Items]
Property and equipment	308.2	297.1
Automated distribution and warehouse equipment [Member]
Property and Equipment, Net [Line Items]
Property and equipment	220	216.3
Shelving, industrial vending, and equipment [Member]
Property and Equipment, Net [Line Items]
Property and equipment	812.9	723.9
Transportation equipment [Member]
Property and Equipment, Net [Line Items]
Property and equipment	76.3	71.7
Construction in progress [Member]
Property and Equipment, Net [Line Items]
Property and equipment	$ 149.3	$ 152.5
Minimum [Member] | Buildings and improvements [Member]
Property and Equipment, Net [Line Items]
Depreciable life in years	15 years
Minimum [Member] | Automated distribution and warehouse equipment [Member]
Property and Equipment, Net [Line Items]
Depreciable life in years	5 years
Minimum [Member] | Shelving, industrial vending, and equipment [Member]
Property and Equipment, Net [Line Items]
Depreciable life in years	3 years
Minimum [Member] | Transportation equipment [Member]
Property and Equipment, Net [Line Items]
Depreciable life in years	3 years
Maximum [Member] | Buildings and improvements [Member]
Property and Equipment, Net [Line Items]
Depreciable life in years	40 years
Maximum [Member] | Automated distribution and warehouse equipment [Member]
Property and Equipment, Net [Line Items]
Depreciable life in years	30 years
Maximum [Member] | Shelving, industrial vending, and equipment [Member]
Property and Equipment, Net [Line Items]
Depreciable life in years	10 years
Maximum [Member] | Transportation equipment [Member]
Property and Equipment, Net [Line Items]
Depreciable life in years	5 years

Accrued Expenses (Details)

Accrued Expenses (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Payables and Accruals [Abstract]
Payroll and related taxes	$ 26	$ 23.2
Bonuses and commissions	19.8	14.2
Profit sharing contribution	10.6	8.7
Insurance reserves	39	34.6
Promotions	31.3	24.9
Indirect taxes	51.1	43.4
Other	16.2	7.4
Accrued expenses	$ 194	$ 156.4

Stockholders' Equity - Addition

Stockholders' Equity - Additional Information (Details) - USD ($) $ / shares in Units, $ in Millions	Jan. 16, 2018	Jan. 02, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2017
Subsequent Event [Line Items]
Dividends paid (in dollars per share)			$ 1.28	$ 1.20	$ 1.12
Options Granted (in shares)						6,628,449
Options vesting and exercisable period, maximum			8 years
Options termination period			9 years
Total intrinsic value of stock options exercised			$ 6.9	$ 23.2	$ 14.2
Total unrecognized stock-based compensation expense			$ 14.6			$ 14.6
Weighted average period over which total unrecognized stock-based compensation expense will be recognized			4 years 1 month 27 days
Total grant date fair value of stock options vested			$ 4.2	7.1	5.1
Total stock-based compensation expense			$ 5.2	$ 4.1	$ 5.8
Subsequent Event [Member]
Subsequent Event [Line Items]
Dividend declared (in dollars per share)	$ 0.37
Options Granted (in shares)		520,601
Option Exercise (Strike) Price (in dollars per share)		$ 55
Closing Stock Price on Date of Grant (in dollars per share)		$ 54.54
Non-employee Director Options Elected (in shares)		21,185
Non-employee Director Option Exercise (Strike) Price (in dollars per share)		$ 55

Stockholders' Equity (Stock Opt

Stockholders' Equity (Stock Options Granted) (Details)	104 Months Ended
	Dec. 31, 2017$ / sharesshares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options Granted (in shares)	6,628,449
Options Outstanding (in shares)	3,948,908
Options Exercisable (in shares)	1,280,499
January, 3, 2017 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options Granted (in shares)	764,789
Option Exercise (Strike) Price (in dollars per share) | $ / shares	$ 47
Closing Stock Price on Date of Grant (in dollars per share) | $ / shares	$ 46.95
Options Outstanding (in shares)	713,097
Options Exercisable (in shares)	0
April 19, 2016 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options Granted (in shares)	845,440
Option Exercise (Strike) Price (in dollars per share) | $ / shares	$ 46
Closing Stock Price on Date of Grant (in dollars per share) | $ / shares	$ 45.74
Options Outstanding (in shares)	738,611
Options Exercisable (in shares)	0
April 21, 2015 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options Granted (in shares)	893,220
Option Exercise (Strike) Price (in dollars per share) | $ / shares	$ 42
Closing Stock Price on Date of Grant (in dollars per share) | $ / shares	$ 41.26
Options Outstanding (in shares)	674,499
Options Exercisable (in shares)	142,072
April 22, 2014 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options Granted (in shares)	955,000
Option Exercise (Strike) Price (in dollars per share) | $ / shares	$ 56
Closing Stock Price on Date of Grant (in dollars per share) | $ / shares	$ 50.53
Options Outstanding (in shares)	567,500
Options Exercisable (in shares)	158,750
April 16, 2013 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options Granted (in shares)	205,000
Option Exercise (Strike) Price (in dollars per share) | $ / shares	$ 54
Closing Stock Price on Date of Grant (in dollars per share) | $ / shares	$ 49.25
Options Outstanding (in shares)	101,750
Options Exercisable (in shares)	55,250
April 17, 2012 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options Granted (in shares)	1,235,000
Option Exercise (Strike) Price (in dollars per share) | $ / shares	$ 54
Closing Stock Price on Date of Grant (in dollars per share) | $ / shares	$ 49.01
Options Outstanding (in shares)	952,001
Options Exercisable (in shares)	772,977
April 19, 2011 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options Granted (in shares)	410,000
Option Exercise (Strike) Price (in dollars per share) | $ / shares	$ 35
Closing Stock Price on Date of Grant (in dollars per share) | $ / shares	$ 31.78
Options Outstanding (in shares)	60,350
Options Exercisable (in shares)	35,350
April 20, 2010 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options Granted (in shares)	530,000
Option Exercise (Strike) Price (in dollars per share) | $ / shares	$ 30
Closing Stock Price on Date of Grant (in dollars per share) | $ / shares	$ 27.13
Options Outstanding (in shares)	79,550
Options Exercisable (in shares)	54,550
April 21, 2009 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options Granted (in shares)	790,000
Option Exercise (Strike) Price (in dollars per share) | $ / shares	$ 27
Closing Stock Price on Date of Grant (in dollars per share) | $ / shares	$ 17.61
Options Outstanding (in shares)	61,550
Options Exercisable (in shares)	61,550

Stockholders' Equity (Fair Valu

Stockholders' Equity (Fair Value Assumptions For Options Granted) (Details)	12 Months Ended
	Dec. 31, 2017$ / shares
January, 3, 2017 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free Interest Rate	1.90%
Expected Life of Option in Years	5 years
Expected Dividend Yield	2.60%
Expected Stock Volatility	24.49%
Estimated Fair Value of Stock Option (in dollars per share)	$ 8.40
April 19, 2016 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free Interest Rate	1.30%
Expected Life of Option in Years	5 years
Expected Dividend Yield	2.60%
Expected Stock Volatility	26.34%
Estimated Fair Value of Stock Option (in dollars per share)	$ 8.18
April 21, 2015 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free Interest Rate	1.30%
Expected Life of Option in Years	5 years
Expected Dividend Yield	2.70%
Expected Stock Volatility	26.84%
Estimated Fair Value of Stock Option (in dollars per share)	$ 7.35
April 22, 2014 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free Interest Rate	1.80%
Expected Life of Option in Years	5 years
Expected Dividend Yield	2.00%
Expected Stock Volatility	28.55%
Estimated Fair Value of Stock Option (in dollars per share)	$ 9.57
April 16, 2013 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free Interest Rate	0.70%
Expected Life of Option in Years	5 years
Expected Dividend Yield	1.60%
Expected Stock Volatility	37.42%
Estimated Fair Value of Stock Option (in dollars per share)	$ 12.66
April 17, 2012 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free Interest Rate	0.90%
Expected Life of Option in Years	5 years
Expected Dividend Yield	1.40%
Expected Stock Volatility	39.25%
Estimated Fair Value of Stock Option (in dollars per share)	$ 13.69
April 19, 2011 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free Interest Rate	2.10%
Expected Life of Option in Years	5 years
Expected Dividend Yield	1.60%
Expected Stock Volatility	39.33%
Estimated Fair Value of Stock Option (in dollars per share)	$ 11.20
April 20, 2010 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free Interest Rate	2.60%
Expected Life of Option in Years	5 years
Expected Dividend Yield	1.50%
Expected Stock Volatility	39.10%
Estimated Fair Value of Stock Option (in dollars per share)	$ 8.14
April 21, 2009 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free Interest Rate	1.90%
Expected Life of Option in Years	5 years
Expected Dividend Yield	1.00%
Expected Stock Volatility	38.80%
Estimated Fair Value of Stock Option (in dollars per share)	$ 3.64

Stockholder's Equity (Summary O

Stockholder's Equity (Summary Of Stock Option Plan Activity) (Details) - $ / shares	12 Months Ended			104 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2017
Options Outstanding
Granted (in shares)				6,628,449
Outstanding as of End of Period (in shares)	3,948,908			3,948,908
Exercisable (in shares)	1,280,499			1,280,499
Stock Option Plan [Member]
Options Outstanding
Outstanding as of Beginning of Period (in shares)	3,757,947	4,530,982
Granted (in shares)	764,789	845,440
Exercised (in shares)	(329,612)	(1,180,242)
Cancelled/Forfeited (in shares)	(244,216)	(438,233)
Outstanding as of End of Period (in shares)	3,948,908	3,757,947	4,530,982	3,948,908
Exercisable (in shares)	1,280,499	1,200,250		1,280,499
Exercise Price
Outstanding as of Beginning of Period (in dollars per share)	$ 46.81	$ 41.49
Granted (in dollars per share)	47	46
Exercised (in dollars per share)	28.59	24.80
Cancelled/Forfeited (in dollars per share)	48.22	49.49
Outstanding as of End of Period (in dollars per share)	48.28	46.81	$ 41.49	$ 48.28
Exercisable (in dollars per share)	$ 50.07	$ 45.93		$ 50.07
Remaining Life
Outstanding	5 years 10 months 20 days	5 years 10 months 6 days	4 years 10 months 20 days
Granted	9 years	8 years 4 months 27 days
Exercisable	3 years 9 months 10 days	3 years 8 months 26 days

Stockholders' Equity (Reconcili

Stockholders' Equity (Reconciliation Of Denominators Used In Computation Of Basic And Diluted Earnings Per Share) (Details) - shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Stockholders' Equity Note [Abstract]
Basic weighted average shares outstanding (in shares)	288,208,435	288,949,525	291,453,107
Weighted shares assumed upon exercise of stock options (in shares)	134,298	207,998	592,335
Diluted weighted average shares outstanding (in shares)	288,342,733	289,157,523	292,045,442

Stockholders' Equity (Summary O

Stockholders' Equity (Summary Of Anti-Dilutive Options Excluded) (Details) - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Stockholders' Equity Note [Abstract]
Options to purchase shares of common stock (in shares)	3,524,401	3,095,343	2,611,367
Weighted average exercise prices of options (in dollars per share)	$ 49.85	$ 50.09	$ 51.89

Retirement Savings Plan (Narrat

Retirement Savings Plan (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Contribution Plan [Abstract]
Expense related to contribution to employees' retirement accounts	$ 10.6	$ 8.7	$ 13.7

Income Taxes (Earnings Before I

Income Taxes (Earnings Before Income Taxes) (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Domestic									$ 809.4	$ 739.4	$ 786
Foreign									63.7	50.3	40.1
Earnings before income taxes	$ 200.8	$ 226	$ 235.4	$ 210.9	$ 180.8	$ 201.2	$ 207.8	$ 199.9	$ 873.1	$ 789.7	$ 826.1

Income Taxes (Components Of Inc

Income Taxes (Components Of Income Tax Expense (Benefit)) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Current
Federal	$ 270.6	$ 223.9	$ 256.7
State	33.2	28.2	31.3
Foreign	20.5	12.6	13.7
Income tax expense	324.3	264.7	301.7
Deferred
Federal	(33.1)	23.2	7.4
State	3.3	1.2	0.2
Foreign	0	1.2	0.4
Income tax expense	(29.8)	25.6	8
Total
Federal	237.5	247.1	264.1
State	36.5	29.4	31.5
Foreign	20.5	13.8	14.1
Income tax expense	$ 294.5	$ 290.3	$ 309.7

Income Taxes (Difference In Inc

Income Taxes (Difference In Income Tax Expense And Expected Expense) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Expected rate of federal income tax expense	35.00%	35.00%	35.00%
Federal income tax expense at the 'expected' rate of 35%	$ 305.6	$ 276.4	$ 289.1
State income taxes, net of federal benefit	21.5	20	21.6
Transition tax	6.5	0	0
Effect of 2018 deferred rate change	(30.8)	0	0
Other, net	(8.3)	(6.1)	(1)
Income tax expense	$ 294.5	$ 290.3	$ 309.7
Effective income tax rate	33.70%	36.80%	37.50%

Income Taxes (Summary Of Tempor

Income Taxes (Summary Of Temporary Differences That Give Rise To Deferred Income Tax Assets And Liabilities) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Deferred income tax assets (liabilities):
Inventory costing and valuation methods	$ 3.6	$ 4.8
Allowance for doubtful accounts	3	4.3
Insurance reserves	8.4	11.5
Promotions payable	1.3	1.7
Stock-based compensation	5.2	6.8
Federal and state benefit of uncertain tax positions	0.9	1.9
Foreign net operating loss and credit carryforwards	4.2	5.1
Foreign valuation allowances	(2.8)	(4)
Other, net	0.8	2.1
Total deferred income tax assets	24.6	34.2
Property and equipment	(75.2)	(114.8)
Total deferred income tax liabilities	(75.2)	(114.8)
Deferred income tax liabilities	$ (50.6)	$ (80.6)

Income Taxes (Reconciliation Of

Income Taxes (Reconciliation Of The Beginning And Ending Amount Of Total Gross Unrecognized Tax Benefits) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Balance at beginning of year:	$ 5.4	$ 5.4
Increase related to prior year tax positions	0.4	0.2
Decrease related to prior year tax positions	(0.5)	0
Increase related to current year tax positions	0.7	0.8
Decrease related to statute of limitation lapses	(1.1)	(1)
Settlements	(0.5)	0
Balance at end of year:	$ 4.4	$ 5.4

Income Taxes (Additional Inform

Income Taxes (Additional Information) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2017USD ($)
Income Tax Disclosure [Abstract]
Estimated income tax expense (benefit), discrete items	$ (24.4)
Estimated reduction in deferred income tax liabilities	30.8
Estimated increase in income tax payable due to transition tax	$ 6.5

Geographic Information (Revenue

Geographic Information (Revenues By Geographic Areas) (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues	$ 1,088.5	$ 1,132.8	$ 1,121.5	$ 1,047.7	$ 947.9	$ 1,013.1	$ 1,014.3	$ 986.7	$ 4,390.5	$ 3,962	$ 3,869.2
United States [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues									3,842.9	3,493.5	3,441.1
Canada [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues									257.6	228.7	223.3
Other foreign countries [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues									$ 290	$ 239.8	$ 204.8

Geographic Information (Long-Li

Geographic Information (Long-Lived Assets By Geographic Areas) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenues from External Customers and Long-Lived Assets [Line Items]
Total long-lived assets	$ 974.8	$ 948.1	$ 867.7
United States [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total long-lived assets	919.5	899.1	821.1
Canada [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total long-lived assets	35.9	33.2	32.3
Other foreign countries [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total long-lived assets	$ 19.4	$ 15.8	$ 14.3

Operating Leases - Additional I

Operating Leases - Additional Information (Details) $ in Millions	Dec. 31, 2017USD ($)
Property Subject to or Available for Operating Lease [Line Items]
Leasehold improvements, net book value	$ 2.5
Leased Vehicles [Member]
Property Subject to or Available for Operating Lease [Line Items]
Aggregate residual value guarantee of pick-up leases	$ 75.5

Operating Leases (Future Minimu

Operating Leases (Future Minimum Lease Payments) (Details) $ in Millions	Dec. 31, 2017USD ($)
Property Subject to or Available for Operating Lease [Line Items]
2,018	$ 133.8
2,019	94.6
2,020	57.9
2,021	27.1
2,022	9.3
2023 and thereafter	2
Total minimum lease payments	324.7
Leased Facilities and Equipment [Member]
Property Subject to or Available for Operating Lease [Line Items]
2,018	96.8
2,019	70.9
2,020	47.5
2,021	25.2
2,022	9.3
2023 and thereafter	2
Total minimum lease payments	251.7
Leased Vehicles [Member]
Property Subject to or Available for Operating Lease [Line Items]
2,018	37
2,019	23.7
2,020	10.4
2,021	1.9
2,022	0
2023 and thereafter	0
Total minimum lease payments	$ 73

Operating Leases (Rent Expense)

Operating Leases (Rent Expense) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Property Subject to or Available for Operating Lease [Line Items]
Rent expense	$ 155.3	$ 152.8	$ 144.1
Leased Facilities and Equipment [Member]
Property Subject to or Available for Operating Lease [Line Items]
Rent expense	109.5	110.1	105.9
Leased Vehicles [Member]
Property Subject to or Available for Operating Lease [Line Items]
Rent expense	$ 45.8	$ 42.7	$ 38.2

Debt Commitments - Debt Obligat

Debt Commitments - Debt Obligations and Letters of Credit Outstanding (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Debt Instrument [Line Items]
Total debt	$ 415	$ 390
Less: Current portion of debt	(3)	(10.5)
Long-term debt	412	379.5
Credit Facility [Member] | Unsecured Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Total debt	280	305
Credit Facility [Member] | Letter of Credit Subfacility [Member]
Debt Instrument [Line Items]
Outstanding letters of credit under unsecured revolving credit facility - contingent obligation	$ 36.3	36.3
Senior Unsecured Promissory Notes [Member] | 2.00% Senior Unsecured Promissory Note Payable [Member]
Debt Instrument [Line Items]
Fixed interest rate per annum	2.00%
Total debt	$ 40	40
Senior Unsecured Promissory Notes [Member] | 2.45% Senior Unsecured Promissory Note Payable [Member]
Debt Instrument [Line Items]
Fixed interest rate per annum	2.45%
Total debt	$ 35	35
Senior Unsecured Promissory Notes [Member] | 3.22% Senior Unsecured Promissory Note Payable [Member]
Debt Instrument [Line Items]
Fixed interest rate per annum	3.22%
Total debt	$ 60	0
Note Payable Under Asset Purchase Agreement [Member]
Debt Instrument [Line Items]
Fixed interest rate per annum	0.56%
Total debt	$ 0	$ 10	$ 15

Debt Commitments - Unsecured Re

Debt Commitments - Unsecured Revolving Credit Facility (Details) - Credit Facility [Member]	12 Months Ended
	Dec. 31, 2017USD ($)
Debt Instrument [Line Items]
Weighted per annum interest rate on outstanding line of credit	2.50%
Minimum [Member]
Debt Instrument [Line Items]
Percentage fee paid for unused portion of credit facility	0.10%
Maximum [Member]
Debt Instrument [Line Items]
Percentage fee paid for unused portion of credit facility	0.125%
LIBOR [Member]
Debt Instrument [Line Items]
Per annum interest rate over LIBOR	0.95%
Unsecured Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Credit facility, maximum borrowing capacity	$ 700,000,000
Letter of Credit Subfacility [Member]
Debt Instrument [Line Items]
Credit facility, maximum borrowing capacity	$ 55,000,000

Debt Commitments - Senior Unsec

Debt Commitments - Senior Unsecured Promissory Notes Payable (Details) - Senior Unsecured Promissory Notes [Member]	Jul. 20, 2016USD ($)	Dec. 31, 2017USD ($)debt_instrument_series	Mar. 31, 2017USD ($)
Debt Instrument [Line Items]
Debt issuance period after effective date	3 years
Maximum aggregate principal amount outstanding	$ 200,000,000
Number of debt instrument series | debt_instrument_series		3
Fixed Rate Notes Payable [Member]
Debt Instrument [Line Items]
Term of debt (no later than 12 years)	12 years
Floating Rate Notes Payable [Member]
Debt Instrument [Line Items]
Term of debt (no later than 12 years)	10 years
2.00% Senior Unsecured Promissory Note Payable [Member]
Debt Instrument [Line Items]
Debt issuance, aggregate principal amount		$ 40,000,000
Fixed interest rate per annum		2.00%
2.45% Senior Unsecured Promissory Note Payable [Member]
Debt Instrument [Line Items]
Debt issuance, aggregate principal amount		$ 35,000,000
Fixed interest rate per annum		2.45%
3.22% Senior Unsecured Promissory Note Payable [Member]
Debt Instrument [Line Items]
Debt issuance, aggregate principal amount		$ 60,000,000	$ 60,000,000
Fixed interest rate per annum		3.22%

Debt Commitments - Note Payable

Debt Commitments - Note Payable Under Asset Purchase Agreement (Details) - USD ($) $ in Millions	Dec. 07, 2015	Dec. 31, 2017	Jun. 30, 2017	Dec. 31, 2016	Dec. 31, 2015
Debt Instrument [Line Items]
Consideration for Apex asset purchase agreement	$ 27
Cash paid for Apex asset purchase agreement		$ 5	$ 5	$ 5	$ 12
Debt		415		390
Note Payable Under Asset Purchase Agreement [Member]
Debt Instrument [Line Items]
Debt		$ 0		$ 10	$ 15
Fixed interest rate per annum		0.56%

Sales by Product Line (Percenta

Sales by Product Line (Percentages Of Sales By Product Line) (Details)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenue from External Customer [Line Items]
Total, percentage of sales	100.00%	100.00%	100.00%
Fasteners [Member]
Revenue from External Customer [Line Items]
Introduced	1,967
Total, percentage of sales	35.60%	36.60%	38.30%
Tools [Member]
Revenue from External Customer [Line Items]
Introduced	1,993
Total, percentage of sales	10.10%	9.90%	9.50%
Cutting tools [Member]
Revenue from External Customer [Line Items]
Introduced	1,996
Total, percentage of sales	5.80%	5.70%	5.60%
Hydraulics & pneumatics [Member]
Revenue from External Customer [Line Items]
Introduced	1,996
Total, percentage of sales	6.80%	6.90%	7.20%
Material handling [Member]
Revenue from External Customer [Line Items]
Introduced	1,996
Total, percentage of sales	6.30%	6.40%	6.50%
Janitorial supplies [Member]
Revenue from External Customer [Line Items]
Introduced	1,996
Total, percentage of sales	7.60%	7.60%	7.50%
Electrical supplies [Member]
Revenue from External Customer [Line Items]
Introduced	1,997
Total, percentage of sales	4.90%	4.80%	4.70%
Welding supplies [Member]
Revenue from External Customer [Line Items]
Introduced	1,997
Total, percentage of sales	4.60%	4.60%	4.70%
Safety supplies [Member]
Revenue from External Customer [Line Items]
Introduced	1,999
Total, percentage of sales	15.20%	14.90%	13.90%
Metals [Member]
Revenue from External Customer [Line Items]
Introduced	2,001
Total, percentage of sales	0.50%	0.50%	0.50%
Direct ship [Member]
Revenue from External Customer [Line Items]
Introduced	2,004
Total, percentage of sales	0.50%	0.50%	0.40%
Office supplies [Member]
Revenue from External Customer [Line Items]
Introduced	2,010
Total, percentage of sales	0.10%	0.10%	0.10%
Other product line [Member]
Revenue from External Customer [Line Items]
Total, percentage of sales	2.00%	1.50%	1.10%

Selected Quarterly Financial 64

Selected Quarterly Financial Data (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Selected Quarterly Financial Information [Abstract]
Net Sales	$ 1,088.5	$ 1,132.8	$ 1,121.5	$ 1,047.7	$ 947.9	$ 1,013.1	$ 1,014.3	$ 986.7	$ 4,390.5	$ 3,962	$ 3,869.2
Gross Profit	531.2	555.9	558.5	518	471.9	499.8	501.6	491.5	2,163.6	1,964.8	1,948.9
Pre-tax Earnings	200.8	226	235.4	210.9	180.8	201.2	207.8	199.9	873.1	789.7	826.1
Net Earnings	$ 152.4	$ 143.1	$ 148.9	$ 134.2	$ 114.8	$ 126.9	$ 131.5	$ 126.2	$ 578.6	$ 499.4	$ 516.4
Basic Net Earnings per Share (in dollars per share)	$ 0.53	$ 0.50	$ 0.52	$ 0.46	$ 0.40	$ 0.44	$ 0.46	$ 0.44	$ 2.01	$ 1.73	$ 1.77
Diluted Net Earnings per Share (in dollars per share)	$ 0.53	$ 0.50	$ 0.52	$ 0.46	$ 0.40	$ 0.44	$ 0.45	$ 0.44	$ 2.01	$ 1.73	$ 1.77
Net earnings, absent impact of tax act	$ 128.1								$ 554.2
Basic net earnings per share, absent impact of tax act (in dollars per share)	$ 0.45								$ 1.92
Diluted net earnings per share, absent impact of tax act (in dollars per share)	$ 0.45								$ 1.92

Schedule II-Valuation and Qua65

Schedule II-Valuation and Qualifying Accounts (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Allowance For Doubtful Accounts [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Year	$ 11.2	$ 11.7	$ 12.6
Additions Charged to Costs and Expenses	8.2	8.5	8.8
Other Additions (Deductions)	0	0	0
Less Deductions	7.5	9	9.7
Balance at End of Year	11.9	11.2	11.7
Insurance Reserves [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Year	34.6	31.8	31.1
Additions Charged to Costs and Expenses	68.2	62.3	54.3
Other Additions (Deductions)	0	0	0
Less Deductions	63.8	59.5	53.6
Balance at End of Year	$ 39	$ 34.6	$ 31.8