Summary of Significant Accounting Policies (Policies)	12 Months Ended
Summary of Significant Accounting Policies (Policies)	Jul. 31, 2018
Accounting Policies [Abstract]
Principles of Consolidation	Principles of Consolidation The Consolidated Financial Statements include the accounts of Donaldson Company, Inc. and all of its majority-owned subsidiaries. All intercompany accounts and transactions have been eliminated. The Company’s three joint ventures are not majority-owned and are accounted for under the equity method. Certain reclassifications to previously reported financial information have been made to conform to the current period presentation.
Use of Estimates	Use of Estimates The preparation of the Consolidated Financial Statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported in the financial statements and accompanying notes. Actual results could differ from those estimates.
Foreign Currency Translation	Foreign Currency Translation For most foreign operations, local currencies are considered the functional currency. Assets and liabilities of non-U.S. dollar functional currency entities are translated to U.S. dollars at year-end exchange rates and the resulting gains and losses arising from the translation of net assets located outside the U.S. are recorded as a cumulative translation adjustment, a component of accumulated other comprehensive loss in the Consolidated Balance Sheets. Elements of the Consolidated Statements of Earnings are translated at average exchange rates in effect during the year.
Cash Equivalents	Cash Equivalents The Company considers all highly liquid temporary investments with an original maturity of three months or less to be cash equivalents. Cash equivalents are carried at cost that approximates market value.
Accounts Receivable and Allowance for Doubtful Accounts	Accounts Receivable and Allowance for Doubtful Accounts Trade accounts receivables are recorded at the invoiced amount and do not bear interest. The allowance for doubtful accounts is the Company’s best estimate of the amount of credit losses in its existing accounts receivable. The Company determines the allowance based on historical write-off experience in the industry, regional economic data and evaluation of specific customer accounts for risk of loss. The Company reviews its allowance for doubtful accounts monthly. Past due balances over 90 days and over a specified amount are reviewed individually for collectability. All other balances are reviewed on a pooled basis by reporting unit and geographic region. Account balances are reserved when the Company determines it is probable the receivable will not be recovered. The Company does not have any off-balance sheet credit exposure related to its customers.
Inventories	Inventories Inventories are stated at the lower of cost and net realizable value. U.S. inventories are valued using the last-in, first-out (LIFO) method while the non-U.S. inventories are valued using the first-in, first-out (FIFO) method.
Property, Plant and Equipment	Property, Plant and Equipment Property, plant and equipment are stated at cost. Additions, improvements or major renewals are capitalized while expenditures that do not enhance or extend the asset’s useful life are charged to expense as incurred. Depreciation is computed using the straight-line method. Depreciation expense was $71.1 million, $68.8 million and $68.8 million in the years ended July 31, 2018, 2017 and 2016, respectively. The estimated useful lives of property, plant and equipment are ten to forty years for buildings, including building improvements, and three to ten years for machinery and equipment.
Internal-Use Software	Internal-Use Software The Company capitalizes direct costs of materials and services used in the development and purchase of internal-use software. Amounts capitalized are amortized on a straight-line basis over a period of five to seven years and are reported as a component of property, plant and equipment.
Goodwill and Other Intangible Assets	Goodwill and Other Intangible Assets Goodwill represents the excess of the purchase price over the fair value of net assets acquired in business combinations under the purchase method of accounting. Other intangible assets, comprised of customer relationships and lists, patents, trademarks and technology, are amortized on a straight-line basis over their estimated useful lives of three to twenty years. Goodwill is assessed for impairment annually or if an event occurs or circumstances change that would indicate the carrying amount may be impaired. The impairment assessment for goodwill is done at a reporting unit level. Reporting units are one level below the operating segment level but can be combined when reporting units within the same operating segment have similar economic characteristics. An impairment loss would be recognized when the carrying amount of the reporting unit’s net assets exceeds the estimated fair value of the reporting unit.
Recoverability of Long-Lived Assets	Recoverability of Long-Lived Assets The Company reviews its long-lived assets, including identifiable intangibles, for impairment when events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. If impairment indicators are present and the estimated future undiscounted cash flows are less than the carrying value of the assets, the carrying value is reduced to the fair market value. The Company recorded an impairment charge of $2.9 million in fiscal 2016 for a partially completed facility in Xuzhou, China. There were no impairment charges recorded in fiscal 2018 or fiscal 2017.
Income Taxes	Income Taxes The provision for income taxes is computed based on the pretax income reported for financial statement purposes. Deferred tax assets and liabilities are recognized for the expected future tax consequences attributed to temporary differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax basis. Deferred tax assets and liabilities are measured using the enacted tax rates expected to apply to taxable income in the years in which those temporary differences are anticipated to reverse. Valuation allowances are recorded to reduce deferred tax assets when it is more-likely-than-not that a tax benefit will not be realized. The Company maintains a reserve for uncertain tax benefits. Benefits of tax return positions are recognized in the financial statements when the position is “more-likely-than-not” to be sustained by the taxing authorities based solely on the technical merits of the position. If the recognition threshold is met, the tax benefit is measured and recognized as the largest amount of tax benefit that in the Company’s judgment is greater than 50% likely to be realized.
Treasury Stock	Treasury Stock Repurchased common stock is stated at cost (determined on an average cost basis) and is presented as a reduction of shareholders’ equity.
Research and Development Expense	Research and Development Expense Research and development expenses include basic scientific research and the application of scientific advances to the development of new and improved products and their uses and are charged against earnings in the year incurred.
Equity Based Compensation	Stock-Based Compensation The Company offers stock-based employee compensation plans, which are more fully described in Note 10. Stock-based employee compensation expense is recognized using the fair-value method for all awards.
Revenue Recognition	Revenue Recognition The Company sells a wide range of filtration solutions into many industries around the globe. Revenue is recognized when both product ownership and the risk of loss have transferred to the customer, the Company has no remaining obligations, the selling price is fixed and determinable and collectability is reasonably assured. The vast majority of the Company’s sales contracts are for standard products with product ownership and risk of loss transferring to the customer when the product has shipped, at which point revenue is recognized. Although less common, the Company does have sales contracts with customers requiring product ownership and risk of loss to transfer at the customer’s location. For these non-standard terms, the Company defers revenue on these product sales until the product has been delivered. For the Company’s Gas Turbine Systems sales, which typically consist of multiple shipments of components that will comprise the entire Gas Turbine Systems project, the Company must carefully monitor the transfer of title related to each portion of a system sale. The Company defers revenue recognition until product ownership and risk of loss has transferred to the customer for all components and when all terms specified in the contract are met, which may include requirements such as the Company delivering technical documentation to the customer or a quality inspection approved by the customer. In limited circumstances, the Company enters into sales contracts that involve multiple elements (such as equipment, replacement filter elements and installation services). In these instances, the Company determines if the multiple elements in the arrangement represent separate units of accounting. If separate units of accounting exist, the price of the entire arrangement is allocated to the separate units of account using the Company’s best estimate of relative selling price if the unit of account was sold separately. Revenue is then recognized separately for each unit of account when the criteria for revenue recognition have been met. Additionally, the Company records estimated discounts and rebates offered to customers as a reduction of sales in the same period revenue is recognized.
Product Warranties	Product Warranties The Company provides for estimated warranty expense at the time of sale and accrues for specific items at the time their existence is known and the amounts are determinable. The Company estimates warranty expense using quantitative measures based on historical warranty claim experience and evaluation of specific customer warranty issues. For a reconciliation of warranty reserves, see Note 8.
Derivative Instruments and Hedging Activities	Derivative Instruments and Hedging Activities The Company recognizes all derivatives on the balance sheet at fair value. Derivatives that are not designated as hedges are adjusted to fair value through income. If the derivative is designated as a hedge, depending on the nature of the hedge, changes in the fair value of derivatives are either offset against the change in fair value of the hedged assets, liabilities or firm commitments through earnings or recognized in shareholders’ equity through other comprehensive loss until the hedged item is recognized. Gains or losses related to the ineffective portion of any hedge are recognized through earnings in the current period.
New Accounting Standards Recently Adopted	New Accounting Standards Recently Adopted In July 2015, the FASB issued Accounting Standards Update (ASU) 2015-11, Inventory (Topic 330): Simplifying the Measurement of Inventory (ASU 2015-11), which amended the guidance requiring companies not using the last-in, first-out (LIFO) method to measure inventory at the lower of cost and net realizable value rather than the lower of cost or market. This accounting guidance was effective for the Company beginning in the first quarter of fiscal 2018 and did not have an impact on its Consolidated Financial Statements. In March 2016, the FASB issued ASU 2016-09, Compensation - Stock Compensation (Topic 718): Improvements to Employee Share-Based Payment Accounting (ASU 2016-09). This update simplifies several aspects of the accounting for share-based payment transactions, including the income tax consequences, classification of awards as either equity or liabilities and classification on the statement of cash flows. ASU 2016-09 was effective for the Company beginning in the first quarter of fiscal 2018 and the guidance affecting the effective tax rate was adopted prospectively. The Consolidated Statements of Cash Flows is also presented retrospectively with the guidance of this new standard and, for the year ended July 31, 2017, resulted in an increase of $7.5 million to net cash provided by operating activities and a corresponding $7.5 million increase to net cash used in financing activities. For the year ended July 31, 2016, the impact was an increase of $5.2 million to net cash provided by operating activities and a corresponding $5.2 million increase to net cash used in financing activities. In August 2016, the FASB issued ASU 2016-15, Statement of Cash Flows (Topic 230) (ASU 2016-15). The new guidance is intended to reduce diversity in practice in how certain transactions are classified in the statement of cash flows. ASU 2016-15 is effective for the Company beginning in fiscal 2019, and early adoption is permitted, provided that all of the amendments are adopted in the same period. The guidance requires application using a retrospective transition method. The Company adopted ASU 2016-15 in the first quarter of fiscal 2018 and it did not have an impact on its Consolidated Financial Statements. In October 2016, the FASB issued ASU No. 2016-16, Income Taxes (Topic 740): Intra-Entity Transfers of Assets Other Than Inventory (ASU 2016-16), which is intended to improve the accounting for the income tax consequences of intra-entity transfers of assets other than inventory. This update removes the current exception in GAAP prohibiting entities from recognizing current and deferred income tax expenses or benefits related to transfer of assets, other than inventory, within the consolidated entity. The current exception to defer the recognition of any tax impact on the transfer of inventory within the consolidated entity until it is sold to a third party remains unaffected. ASU 2016-16 is effective for the Company beginning in fiscal 2019, and early adoption is permitted. The Company adopted ASU 2016-16 in the first quarter of fiscal 2018 and it did not have an impact on its Consolidated Financial Statements. In May 2017, the FASB issued ASU 2017-09, Compensation - Stock Compensation (Topic 718) (ASU 2017-09). The amendments in ASU 2017-09 provide guidance about which changes to the terms or conditions of a share-based payment award require an entity to apply modification accounting in Topic 718. ASU 2017-09 is effective for the Company beginning in fiscal 2019, and early adoption is permitted. The Company adopted ASU 2017-09 in the first quarter of fiscal 2018 and it did not have an impact on its Consolidated Financial Statements. New Accounting Standards Not Yet Adopted In May 2014, the FASB issued ASU 2014-09, Revenue from Contracts with Customers (Topic 606) (ASU 2014-09), which amended revenue recognition guidance to clarify the principles for recognizing revenue from contracts with customers. The guidance requires an entity to recognize revenue to depict the transfer of goods or services to customers in an amount that reflects the consideration to which an entity expects to be entitled in exchange for those goods or services. The guidance 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 about customer contracts, significant judgments and changes in judgments and assets recognized from the costs to obtain or fulfill a contract. In 2016, the FASB issued ASU 2016-08, ASU 2016-10, ASU 2016-11, ASU 2016-12 and ASU 2016-20 to clarify, among other things, the implementation guidance related to principal versus agent considerations, identifying performance obligations and accounting for licenses of intellectual property. This accounting guidance is effective for the Company beginning in the first quarter of fiscal 2019. The amendments in this update are to be applied on a retrospective basis, either to each prior reporting period presented (full retrospective method) or by presenting the cumulative effect of applying the update recognized at the date of initial application (modified retrospective method). The Company has made the decision that it will adopt the standard using the modified retrospective method, applying the guidance to those contracts which were not completed as of July 31, 2018. A project team has been established, has conducted surveys of the businesses, performed revenue contract analyses to gather information and identified where potential differences result in applying the requirements of the new standard. This change will impact one set of contracts within the Engine Products segment in which Donaldson is deemed to be the principal under the new standard because the Company has control of the products prior to the sale of those products to the customer. For these contracts, the current practice of recognizing revenue on a net basis, in which the amount of net sales recorded is the net amount retained after paying product costs to suppliers, will change to recognizing revenue on a gross basis, in which the amount of net sales recorded is the gross amount received from the customer, with corresponding product costs recorded as cost of sales. This change will not result in a transition adjustment under the modified retrospective method of adoption since there is not an impact to the timing of revenue recognition, but the change to a gross basis of accounting for those contracts impacted will increase net sales and cost of sales on a prospective basis. The increase in net sales and cost of sales would have been $21.9 million for the year ended July 31, 2018 if the new revenue guidance would have been applied during that period. While the assessment is ongoing, the Company has not identified any material impact on its Consolidated Financial Statements, other than the change to gross accounting for the set of contracts described above. In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842) (ASU 2016-02), which amends the guidance requiring companies to recognize assets and liabilities for leases with lease terms of more than twelve months. The new guidance will require companies to record both capital and operating leases on the balance sheet. This accounting guidance is effective for the Company beginning in the first quarter of fiscal 2020 on a modified retrospective basis. The Company is evaluating the impact of the adoption of ASU 2016-02 on its Consolidated Financial Statements. In June 2016, the FASB issued ASU 2016-13, Measurement of Credit Losses on Financial Instruments (ASU 2016-13). This guidance introduces a new model for recognizing credit losses on financial instruments based on an estimate of current expected credit losses. Financial instruments impacted include accounts receivable, trade receivables, other financial assets measured at amortized cost and other off-balance sheet credit exposures. The new guidance is effective for the Company beginning in the first quarter of fiscal 2021, with early adoption permitted. The Company is evaluating the effect of ASU 2016-13 on its Consolidated Financial Statements. In January 2017, the FASB issued ASU 2017-01, Business Combinations: Clarifying the Definition of a Business (ASU 2017-01). The new guidance provides a more robust framework to use in determining when a set of assets and activities is a business. The amendments provide more consistency in applying the guidance, reduce the costs of application and make the definition of a business more operable. ASU 2017-01 is effective for the Company beginning in the first quarter of fiscal 2019. The Company does not expect the application of ASU 2017-01 will have a material impact on its Consolidated Financial Statements. In March 2017, the FASB issued ASU 2017-07, Compensation - Retirement Benefits (Topic 715) (ASU 2017-07). The new guidance requires employers to disaggregate and present separately the current service cost component from the other components of net benefit cost within the consolidated statement of earnings. ASU 2017-07 is effective for the Company beginning in the first quarter of fiscal 2019. The adoption of this standard using the retrospective method will result in a reclassification of net benefit costs in its Consolidated Statements of Earnings, decreasing operating income while increasing other income, net. The amounts of the reclassification are anticipated to be approximately $3.0 million and $5.0 million for the years ended July 31, 2018 and 2017, respectively. In August 2017, the FASB issued ASU 2017-12, Derivatives and Hedging: Targeted Improvements to Accounting for Hedging Activities (ASU 2017-12), which improves the financial reporting of hedging relationships to better portray the economic results of an entity's risk management activities in its financial statements and make certain targeted improvements to simplify the application of the hedge accounting guidance. The guidance expands the ability to hedge non-financial and financial risk components, reduces complexity in fair value hedges of interest rate risk, eliminates the requirement to separately measure and report hedge ineffectiveness, as well as eases certain hedge effectiveness assessment requirements. ASU 2017-12 is effective for the Company beginning in the first quarter of fiscal 2020, and early adoption is permitted. The Company does not expect the adoption of ASU 2017-12 will have a material impact on its Consolidated Financial Statements. In February 2018, the FASB issued ASU 2018-02, Income Statement - Reporting Comprehensive Income (Topic 220): Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income (ASU 2018-02). The guidance allows a company to elect to reclassify from accumulated other comprehensive income (AOCI) to retained earnings the stranded tax effects from the adoption of the newly enacted federal corporate tax rate as a result of the U.S. Tax Cuts and Jobs Act. The amount of the reclassification is calculated as the difference between the amount initially charged to other comprehensive income (OCI) at the time of the previously enacted tax rate that remains in AOCI and the amount that would have been charged using the newly enacted tax rate, excluding any valuation allowance previously charged to income. ASU 2018-02 is effective for the Company beginning in the first quarter of fiscal 2020, and early adoption is permitted. The Company is evaluating the impact of the adoption of ASU 2018-02 on its Consolidated Financial Statements.
Earnings Per Share	The Company’s basic net earnings per share is computed by dividing net earnings by the weighted average number of outstanding common shares. The Company’s diluted net earnings per share is computed by dividing net earnings by the weighted average number of outstanding common shares and common share equivalents related to stock options and stock incentive plans. Certain outstanding options are excluded from the diluted net earnings per share calculations because their exercise prices are greater than the average market price of the Company’s common stock during those periods.