Fastenal (FAST) 10-Q 16 Oct 17 2017 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2017	Oct. 10, 2017
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2017
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	Q3
Trading Symbol	fast
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		287,390,374

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 133.4	$ 112.7
Trade accounts receivable, net of allowance for doubtful accounts of $11.4 and $11.2, respectively	632.1	499.7
Inventories	1,047	993
Prepaid income taxes	0	12.9
Other current assets	117.7	102.5
Total current assets	1,930.2	1,720.8
Property and equipment, net	889.3	899.7
Other assets	82.1	48.4
Total assets	2,901.6	2,668.9
Current liabilities:
Current portion of debt	8	10.5
Accounts payable	147.1	108.8
Accrued expenses	198.7	156.4
Income taxes payable	6.6	0
Total current liabilities	360.4	275.7
Long-term debt	432	379.5
Deferred income tax liabilities	82.9	80.6
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, 287,383,174 and 289,161,924 shares issued and outstanding, respectively	2.9	2.9
Additional paid-in capital	1.3	37.4
Retained earnings	2,050.2	1,940.1
Accumulated other comprehensive loss	(28.1)	(47.3)
Total stockholders' equity	2,026.3	1,933.1
Total liabilities and stockholders' equity	$ 2,901.6	$ 2,668.9

Condensed Consolidated Balance3

Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016
Current assets:
Trade accounts receivable, allowance for doubtful accounts	$ 11.4	$ 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)	287,383,174	289,161,924
Outstanding (in shares)	287,383,174	289,161,924

Condensed Consolidated Statemen

Condensed Consolidated Statements of Earnings - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Income Statement [Abstract]
Net sales	$ 1,132.8	$ 1,013.1	$ 3,302	$ 3,014.1
Cost of sales	576.9	513.3	1,669.6	1,521.2
Gross profit	555.9	499.8	1,632.4	1,492.9
Operating and administrative expenses	327.5	297.1	955	879.9
Gain on sale of property and equipment	(0.1)	(0.2)	(1.1)	(0.3)
Operating income	228.5	202.9	678.5	613.3
Interest income	0.1	0.1	0.3	0.3
Interest expense	(2.6)	(1.8)	(6.5)	(4.7)
Earnings before income taxes	226	201.2	672.3	608.9
Income tax expense	82.9	74.3	246.1	224.3
Net earnings	$ 143.1	$ 126.9	$ 426.2	$ 384.6
Basic net earnings per share (in dollars per share)	$ 0.50	$ 0.44	$ 1.48	$ 1.33
Diluted net earnings per share (in dollars per share)	$ 0.50	$ 0.44	$ 1.48	$ 1.33
Basic weighted average shares outstanding (in shares)	287,456,943	288,995,492	288,451,470	288,907,934
Diluted weighted average shares outstanding (in shares)	287,578,043	289,149,606	288,591,574	289,135,842

Condensed Consolidated Stateme5

Condensed Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Statement of Comprehensive Income [Abstract]
Net earnings	$ 143.1	$ 126.9	$ 426.2	$ 384.6
Other comprehensive income, net of tax:
Foreign currency translation adjustments (net of tax of $0.0 in 2017 and 2016)	8.2	(2.9)	19.2	9.3
Comprehensive income	$ 151.3	$ 124	$ 445.4	$ 393.9

Condensed Consolidated Stateme6

Condensed Consolidated Statements of Comprehensive Income (Parenthetical) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Statement of Comprehensive Income [Abstract]
Foreign currency translation adjustments, tax	$ 0	$ 0	$ 0	$ 0

Condensed Consolidated Stateme7

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Cash flows from operating activities:
Net earnings	$ 426.2	$ 384.6
Adjustments to reconcile net earnings to net cash provided by operating activities, net of acquisition:
Depreciation of property and equipment	92.3	74.5
Gain on sale of property and equipment	(1.1)	(0.3)
Bad debt expense	6.2	6.6
Deferred income taxes	2.3	2.7
Stock-based compensation	4	2.9
Amortization of intangible assets	2.8	0.4
Changes in operating assets and liabilities, net of acquisition:
Trade accounts receivable	(126.2)	(80.4)
Inventories	(31.2)	(51)
Other current assets	(15.2)	11.6
Accounts payable	35.9	(8.2)
Accrued expenses	42.3	3.8
Income taxes	19.5	39.8
Other	(1.9)	(0.1)
Net cash provided by operating activities	455.9	386.9
Cash flows from investing activities:
Purchases of property and equipment	(82.7)	(162)
Proceeds from sale of property and equipment	6.2	4.6
Cash paid for acquisition	(58.7)	0
Other	(3)	(0.2)
Net cash used in investing activities	(138.2)	(157.6)
Cash flows from financing activities:
Proceeds from debt obligations	805	760
Payments against debt obligations	(750)	(680)
Proceeds from exercise of stock options	3.5	25
Purchases of common stock	(82.6)	(59.5)
Payments of dividends	(277.1)	(259.9)
Net cash used in financing activities	(301.2)	(214.4)
Effect of exchange rate changes on cash and cash equivalents	4.2	3.1
Net increase in cash and cash equivalents	20.7	18
Cash and cash equivalents at beginning of period	112.7	129
Cash and cash equivalents at end of period	133.4	147
Supplemental disclosure of cash flow information:
Cash paid for interest	6.1	4.4
Net cash paid for income taxes	$ 223.8	$ 181.2

Basis of Presentation

Basis of Presentation	9 Months Ended
	Sep. 30, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Presentation	(1) Basis of Presentation The accompanying unaudited condensed consolidated financial statements of Fastenal Company and subsidiaries (collectively referred to as the Company, Fastenal, or by terms such as we, our, or us) have been prepared in accordance with U.S. generally accepted accounting principles ('GAAP') for interim financial information. They do not include all information and footnotes required by U.S. GAAP for complete financial statements. However, except as described herein, there has been no material change in the information disclosed in the Notes to Consolidated Financial Statements included in our consolidated financial statements as of and for the year ended December 31, 2016 . In the opinion of management, all adjustments (consisting of normal recurring accruals) considered necessary for a fair presentation have been included. Recently Adopted Accounting Pronouncements Effective January 1, 2017, we adopted the Financial Accounting Standards Board ('FASB') Accounting Standards Update ('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 Condensed Consolidated Statements of Cash Flows. As a result of the adoption, on a prospective basis, for the nine and three month periods ended September 30, 2017, we recognized $0.5 and $0.0 , respectively, 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 Condensed Consolidated Statement of Cash Flows for the nine months ended September 30, 2016, which resulted in a reclassification of excess tax benefits from stock-based compensation of $5.5 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. 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 defers 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 is 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 defers 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 cumulative catch-up transition 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. While we are still in the process of evaluating the effect of adoption on our consolidated financial statements and are currently assessing our contracts with customers, we do not currently expect a material impact on our results of operations, cash flows or financial position. The majority of our revenue arrangements generally consist of a single performance obligation to transfer promised goods or services. We anticipate we will expand our consolidated financial statement disclosures in order to comply with the ASU. We have not yet decided on our transition method upon adoption, but plan to select a transition method in the fourth quarter of 2017. 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 Condensed 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	9 Months Ended
	Sep. 30, 2017
Business Combinations [Abstract]
Acquisition	(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 contributed in the past, while providing 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 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. The fair value of the contingent consideration arrangement as of September 30, 2017, estimated by applying the income approach, which is a Level 3 measurement under the fair value hierarchy, was $0.6 . Assuming payment of $0.6 of the contingent consideration arrangement, the total consideration for the acquisition will be $59.3 . We funded the purchase price for the acquisition with the proceeds from the issuance during the first quarter of 2017 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 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 condensed consolidated statement of earnings for the periods ended September 30, 2017, and the pro forma net sales and net earnings of the combined entity had the acquisition occurred on January 1, 2016, are: Nine-month Period Three-month Period 2017 2016 2017 2016 Net sales $ 40.4 36.7 $ 13.4 12.7 Net earnings $ 4.6 3.7 $ 1.4 1.2

Stockholders' Equity

Stockholders' Equity	9 Months Ended
	Sep. 30, 2017
Stockholders' Equity Note [Abstract]
Stockholders' Equity	(3) Stockholders' Equity Dividends On October 10, 2017 , our board of directors declared a dividend of $0.32 per share of common stock. This dividend is to be paid in cash on November 22, 2017 to shareholders of record at the close of business on October 25, 2017 . Since 2011, we have paid quarterly dividends. Our board of directors expects to continue paying quarterly dividends, provided the future determination as to payment of dividends will depend on the financial needs of the Company and such other factors as deemed relevant by the board of directors. The following table presents the dividends either paid previously or declared by our board of directors for future payment on a per share basis: 2017 2016 First quarter $ 0.32 0.30 Second quarter 0.32 0.30 Third quarter 0.32 0.30 Fourth quarter 0.32 0.30 Total $ 1.28 1.20 Stock Options The following tables summarize the details of options granted under our stock option plan that were still outstanding as of September 30, 2017 , and the assumptions used to value these 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 September 30, 2017 Date of Grant Options Outstanding Options Exercisable January 3, 2017 764,789 $ 47.00 $ 46.95 725,542 — April 19, 2016 845,440 $ 46.00 $ 45.74 757,522 — April 21, 2015 893,220 $ 42.00 $ 41.26 700,746 — April 22, 2014 955,000 $ 56.00 $ 50.53 572,500 116,250 April 16, 2013 205,000 $ 54.00 $ 49.25 104,250 57,250 April 17, 2012 1,235,000 $ 54.00 $ 49.01 957,938 776,103 April 19, 2011 410,000 $ 35.00 $ 31.78 72,550 47,550 April 20, 2010 530,000 $ 30.00 $ 27.13 107,800 82,800 April 21, 2009 790,000 $ 27.00 $ 17.61 221,650 221,650 Total 6,628,449 4,220,498 1,301,603 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. Compensation expense equal to the grant date fair value is recognized for all of these awards over the vesting period. The stock-based compensation expense for the nine -month periods ended September 30, 2017 and 2016 was $4.0 and $2.9 , respectively. Unrecognized stock-based compensation expense related to outstanding unvested stock options as of September 30, 2017 was $15.9 and is expected to be recognized over a weighted average period of 4.37 years . Any future changes in estimated forfeitures will impact this amount. 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 per share calculation because they were anti-dilutive: Nine-month Period Three-month Period Reconciliation 2017 2016 2017 2016 Basic weighted average shares outstanding 288,451,470 288,907,934 287,456,943 288,995,492 Weighted shares assumed upon exercise of stock options 140,104 227,908 121,100 154,114 Diluted weighted average shares outstanding 288,591,574 289,135,842 287,578,043 289,149,606 Nine-month Period Three-month Period Summary of Anti-dilutive Options Excluded 2017 2016 2017 2016 Options to purchase shares of common stock 3,881,605 3,061,217 3,848,126 3,335,439 Weighted average exercise price of options $ 49.21 50.17 $ 49.18 49.67 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.

Income Taxes

Income Taxes	9 Months Ended
	Sep. 30, 2017
Income Tax Disclosure [Abstract]
Income Taxes	(4) Income Taxes 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 and foreign examinations and 2013 in the case of state and local examinations. As of September 30, 2017 and 2016 , liabilities recorded related to gross unrecognized tax benefits were $4.5 and $5.3 , respectively. Included in these liabilities 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. We do not anticipate significant changes in total unrecognized tax benefits during the next twelve months.

Operating Leases

Operating Leases	9 Months Ended
	Sep. 30, 2017
Leases, Operating [Abstract]
Operating Leases	(5) Operating Leases 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 is approximately $78.7 . 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 is immaterial at September 30, 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	9 Months Ended
	Sep. 30, 2017
Debt Disclosure [Abstract]
Debt Commitments	(6) Debt Commitments Credit Facility, Notes Payable, and Commitments Debt obligations and letters of credit outstanding at the end of each period consisted of the following: September 30, 2017 December 31, 2016 Outstanding loans under unsecured revolving credit facility $ 300.0 305.0 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 5.0 10.0 Total debt 440.0 390.0 Less: Current portion of debt (8.0 ) (10.5 ) Long-term debt $ 432.0 379.5 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 September 30, 2017 was approximately 2.2% . 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 senior unsecured 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 the 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 under 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 includes a transition arrangement which requires us to assume responsibility for certain software that is licensed by Apex. The total consideration for the assets is $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 is payable in installments pursuant to an unsecured note. The first $5.0 installment was paid in December 2016, the second $5.0 installment was paid in June 2017, and the final installment of $5.0 will be paid in December 2017. The note bears interest at an annual rate of 0.56% . Interest on the unpaid principal balance of the note is due and payable on the last day of each calendar quarter.

Legal Contingencies

Legal Contingencies	9 Months Ended
	Sep. 30, 2017
Commitments and Contingencies Disclosure [Abstract]
Legal Contingencies	(7) Legal Contingencies The nature of our potential exposure to legal contingencies is described in our 2016 annual report on Form 10-K in Note 9 of the Notes to Consolidated Financial Statements. As of September 30, 2017 , there were no litigation matters that we consider to be probable or reasonably possible to have a material adverse outcome.

Subsequent Events

Subsequent Events	9 Months Ended
	Sep. 30, 2017
Subsequent Events [Abstract]
Subsequent Events	(8) Subsequent Events We evaluated all subsequent event activity and concluded that no subsequent events have occurred that would require recognition in the condensed consolidated financial statements or disclosure in the Notes to Condensed Consolidated Financial Statements, with the exception of the dividend disclosed in Note 3 'Stockholders' Equity'.

Basis of Presentation (Policies

Basis of Presentation (Policies)	9 Months Ended
	Sep. 30, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Presentation	The accompanying unaudited condensed consolidated financial statements of Fastenal Company and subsidiaries (collectively referred to as the Company, Fastenal, or by terms such as we, our, or us) have been prepared in accordance with U.S. generally accepted accounting principles ('GAAP') for interim financial information. They do not include all information and footnotes required by U.S. GAAP for complete financial statements. However, except as described herein, there has been no material change in the information disclosed in the Notes to Consolidated Financial Statements included in our consolidated financial statements as of and for the year ended December 31, 2016 . In the opinion of management, all adjustments (consisting of normal recurring accruals) considered necessary for a fair presentation have been included.
Recently Adopted and Recently Issued Accounting Pronouncements	Recently Adopted Accounting Pronouncements Effective January 1, 2017, we adopted the Financial Accounting Standards Board ('FASB') Accounting Standards Update ('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 Condensed Consolidated Statements of Cash Flows. As a result of the adoption, on a prospective basis, for the nine and three month periods ended September 30, 2017, we recognized $0.5 and $0.0 , respectively, 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 Condensed Consolidated Statement of Cash Flows for the nine months ended September 30, 2016, which resulted in a reclassification of excess tax benefits from stock-based compensation of $5.5 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. 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 defers 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 is 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 defers 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 cumulative catch-up transition 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. While we are still in the process of evaluating the effect of adoption on our consolidated financial statements and are currently assessing our contracts with customers, we do not currently expect a material impact on our results of operations, cash flows or financial position. The majority of our revenue arrangements generally consist of a single performance obligation to transfer promised goods or services. We anticipate we will expand our consolidated financial statement disclosures in order to comply with the ASU. We have not yet decided on our transition method upon adoption, but plan to select a transition method in the fourth quarter of 2017. 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 Condensed 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)	9 Months Ended
	Sep. 30, 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 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 condensed consolidated statement of earnings for the periods ended September 30, 2017, and the pro forma net sales and net earnings of the combined entity had the acquisition occurred on January 1, 2016, are: Nine-month Period Three-month Period 2017 2016 2017 2016 Net sales $ 40.4 36.7 $ 13.4 12.7 Net earnings $ 4.6 3.7 $ 1.4 1.2

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	9 Months Ended
	Sep. 30, 2017
Stockholders' Equity Note [Abstract]
Schedule of Dividends Paid Previously or Declared	The following table presents the dividends either paid previously or declared by our board of directors for future payment on a per share basis: 2017 2016 First quarter $ 0.32 0.30 Second quarter 0.32 0.30 Third quarter 0.32 0.30 Fourth quarter 0.32 0.30 Total $ 1.28 1.20
Stock Options Granted	The following tables summarize the details of options granted under our stock option plan that were still outstanding as of September 30, 2017 , and the assumptions used to value these 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 September 30, 2017 Date of Grant Options Outstanding Options Exercisable January 3, 2017 764,789 $ 47.00 $ 46.95 725,542 — April 19, 2016 845,440 $ 46.00 $ 45.74 757,522 — April 21, 2015 893,220 $ 42.00 $ 41.26 700,746 — April 22, 2014 955,000 $ 56.00 $ 50.53 572,500 116,250 April 16, 2013 205,000 $ 54.00 $ 49.25 104,250 57,250 April 17, 2012 1,235,000 $ 54.00 $ 49.01 957,938 776,103 April 19, 2011 410,000 $ 35.00 $ 31.78 72,550 47,550 April 20, 2010 530,000 $ 30.00 $ 27.13 107,800 82,800 April 21, 2009 790,000 $ 27.00 $ 17.61 221,650 221,650 Total 6,628,449 4,220,498 1,301,603
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 per share calculation because they were anti-dilutive: Nine-month Period Three-month Period Reconciliation 2017 2016 2017 2016 Basic weighted average shares outstanding 288,451,470 288,907,934 287,456,943 288,995,492 Weighted shares assumed upon exercise of stock options 140,104 227,908 121,100 154,114 Diluted weighted average shares outstanding 288,591,574 289,135,842 287,578,043 289,149,606
Anti-Dilutive Options Excluded	Nine-month Period Three-month Period Summary of Anti-dilutive Options Excluded 2017 2016 2017 2016 Options to purchase shares of common stock 3,881,605 3,061,217 3,848,126 3,335,439 Weighted average exercise price of options $ 49.21 50.17 $ 49.18 49.67

Debt Commitments (Tables)

Debt Commitments (Tables)	9 Months Ended
	Sep. 30, 2017
Debt Disclosure [Abstract]
Schedule of Debt Obligations and Letters of Credit Outstanding	Debt obligations and letters of credit outstanding at the end of each period consisted of the following: September 30, 2017 December 31, 2016 Outstanding loans under unsecured revolving credit facility $ 300.0 305.0 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 5.0 10.0 Total debt 440.0 390.0 Less: Current portion of debt (8.0 ) (10.5 ) Long-term debt $ 432.0 379.5 Outstanding letters of credit under unsecured revolving credit facility - contingent obligation $ 36.3 36.3

Basis of Presentation - Additio

Basis of Presentation - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2017	Sep. 30, 2016
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Excess tax benefits from stock-based compensation	$ 0	$ 0.5
Reclassification offsetting cash flows used in financing activities		301.2	$ 214.4
Reclassification to cash flows provided by operating activities		$ 455.9	386.9
Accounting Standards Update 2016-09 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Reclassification offsetting cash flows used in financing activities			5.5
Reclassification to cash flows provided by operating activities			$ 5.5

Acquisition - Additional Inform

Acquisition - Additional Information (Details) - USD ($)	Mar. 31, 2017	Sep. 30, 2017	Sep. 30, 2017
Senior 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	$ 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	2,500,000
Fair value of contingent consideration arrangement		$ 600,000	600,000
Total consideration including fair value of contingent consideration arrangement			$ 59,300,000

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) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Actual sales and earnings
Net sales	$ 1,132.8	$ 1,013.1	$ 3,302	$ 3,014.1
Net earnings	143.1	126.9	426.2	384.6
Manufacturers Supply Company [Member]
Business Acquisition [Line Items]
Net sales		12.7	40.4	36.7
Net earnings		$ 1.2	$ 4.6	$ 3.7
Actual sales and earnings
Net sales	13.4
Net earnings	$ 1.4

Stockholders' Equity - Addition

Stockholders' Equity - Additional Information (Details) - USD ($) $ / shares in Units, $ in Millions	Oct. 10, 2017	Sep. 30, 2017	Sep. 30, 2016
Stockholders' Equity Note [Abstract]
Options vesting and exercisable period, maximum		8 years
Options termination period		9 years
Total stock-based compensation expense		$ 4	$ 2.9
Total unrecognized stock-based compensation expense		$ 15.9
Weighted average period over which total unrecognized stock-based compensation expense will be recognized		4 years 4 months 13 days
Subsequent Event [Member]
Subsequent Event [Line Items]
Dividend declared (in dollars per share)	$ 0.32

Stockholders' Equity - Schedule

Stockholders' Equity - Schedule of Dividends Paid Previously or Declared (Details) - $ / shares	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
Dividends Per Share [Line Items]
Dividends paid (in dollars per share)		$ 0.32	$ 0.32	$ 0.32	$ 0.30	$ 0.30	$ 0.30	$ 0.30		$ 1.20
Forecast [Member]
Dividends Per Share [Line Items]
Dividends paid (in dollars per share)	$ 0.32								$ 1.28

Stockholders' Equity - Stock Op

Stockholders' Equity - Stock Options Granted (Details)	101 Months Ended
	Sep. 30, 2017$ / sharesshares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options Granted (in shares)	6,628,449
Options Outstanding (in shares)	4,220,498
Options Exercisable (in shares)	1,301,603
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)	725,542
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)	757,522
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)	700,746
Options Exercisable (in shares)	0
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)	572,500
Options Exercisable (in shares)	116,250
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)	104,250
Options Exercisable (in shares)	57,250
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)	957,938
Options Exercisable (in shares)	776,103
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)	72,550
Options Exercisable (in shares)	47,550
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)	107,800
Options Exercisable (in shares)	82,800
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)	221,650
Options Exercisable (in shares)	221,650

Stockholders' Equity - Fair Val

Stockholders' Equity - Fair Value Assumptions for Options Granted (Details)	9 Months Ended
	Sep. 30, 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

Stockholders' Equity - Reconcil

Stockholders' Equity - Reconciliation of Denominators used in Computation of Basic and Diluted Earnings Per Share (Details) - shares	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Stockholders' Equity Note [Abstract]
Basic weighted average shares outstanding (in shares)	287,456,943	288,995,492	288,451,470	288,907,934
Weighted shares assumed upon exercise of stock options (in shares)	121,100	154,114	140,104	227,908
Diluted weighted average shares outstanding (in shares)	287,578,043	289,149,606	288,591,574	289,135,842

Stockholders' Equity - Summary

Stockholders' Equity - Summary of Anti-Dilutive Options Excluded (Details) - $ / shares	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Stockholders' Equity Note [Abstract]
Options to purchase shares of common stock (in shares)	3,848,126	3,335,439	3,881,605	3,061,217
Weighted average exercise price of options (in dollars per share)	$ 49.18	$ 49.67	$ 49.21	$ 50.17

Income Taxes - Additional Infor

Income Taxes - Additional Information (Details) - USD ($) $ in Millions	Sep. 30, 2017	Sep. 30, 2016
Income Tax Disclosure [Abstract]
Liabilities recorded related to gross unrecognized tax benefits	$ 4.5	$ 5.3

Operating Leases - Additional I

Operating Leases - Additional Information (Details) $ in Millions	Sep. 30, 2017USD ($)
Leased Vehicles [Member]
Property Subject to or Available for Operating Lease [Line Items]
Aggregate residual value guarantee of pick-up leases	$ 78.7

Debt Commitments - Debt Obligat

Debt Commitments - Debt Obligations and Letters of Credit Outstanding (Details) - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016	Dec. 31, 2015
Debt Instrument [Line Items]
Total debt	$ 440	$ 390
Less: Current portion of debt	(8)	(10.5)
Long-term debt	432	379.5
Credit Facility [Member] | Unsecured Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Total debt	300	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]
Total debt	$ 40	40
Fixed interest rate per annum	2.00%
Senior Unsecured Promissory Notes [Member] | 2.45% Senior Unsecured Promissory Note Payable [Member]
Debt Instrument [Line Items]
Total debt	$ 35	35
Fixed interest rate per annum	2.45%
Senior Unsecured Promissory Notes [Member] | 3.22% Senior Unsecured Promissory Note Payable [Member]
Debt Instrument [Line Items]
Total debt	$ 60	0
Fixed interest rate per annum	3.22%
Note Payable Under Asset Purchase Agreement [Member]
Debt Instrument [Line Items]
Total debt	$ 5	$ 10	$ 15
Fixed interest rate per annum	0.56%

Debt Commitments - Unsecured Re

Debt Commitments - Unsecured Revolving Credit Facility (Details) - Credit Facility [Member]	9 Months Ended
	Sep. 30, 2017USD ($)
Debt Instrument [Line Items]
Weighted per annum interest rate on outstanding line of credit	2.20%
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 ($)	Sep. 30, 2017USD ($)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	Sep. 30, 2017
Debt Instrument [Line Items]
Consideration for Apex asset purchase agreement	$ 27
Cash paid for asset purchase agreement			$ 5	$ 5	$ 12
Debt				390		$ 440
Note Payable Under Asset Purchase Agreement [Member]
Debt Instrument [Line Items]
Debt				$ 10	$ 15	$ 5
Fixed interest rate per annum						0.56%
Scenario, Forecast [Member]
Debt Instrument [Line Items]
Cash paid for asset purchase agreement		$ 5