Income Taxes	9 Months Ended
Feb. 28, 2018
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes In the normal course of business, Cintas provides for uncertain tax positions and the related interest and adjusts its unrecognized tax benefits and accrued interest accordingly. As of February 28, 2018 and May 31, 2017, recorded unrecognized tax benefits were $18.5 million and $12.6 million, respectively, and are included in long-term accrued liabilities on the consolidated condensed balance sheet. The increase in the liability for the nine months ended February 28, 2018 is primarily related to an adjustment to the preliminary purchase price allocation for the G&K acquisition. All U.S. federal income tax returns are closed to audit through fiscal 2014. Cintas is currently in various audits in certain foreign jurisdictions and certain domestic states. The years under foreign and domestic state audits cover fiscal years back to 2013. Based on the resolution of the various audits and other potential regulatory developments, it is reasonably possible that the balance of unrecognized tax benefits would not change for the fiscal year ending May 31, 2018. The majority of Cintas' operations are in North America. Cintas is required to file federal income tax returns, as well as state income tax returns in a majority of the domestic states and also in certain Canadian provinces. At times, Cintas is subject to audits in these jurisdictions. The audits, by nature, are sometimes complex and can require several years to resolve. The final resolution of any such tax audit could result in either a reduction in Cintas' accruals or an increase in its income tax provision, either of which could have an impact on the consolidated condensed results of operations in any given period. On December 22, 2017, the President signed into legislation the Tax Cuts and Jobs Act (the Tax Act). Among other changes, the Tax Act reduces the U.S. corporate tax rate from 35% to 21% and requires companies to pay a one-time transition tax on earnings of foreign subsidiaries. The Tax Act also includes provisions that are expected to offset some of the benefit of the U.S. corporate tax rate reduction, including the repeal of the deduction for domestic production activities and the expansion of the limitation on the deduction of certain executive compensation. In addition, the Tax Act alters the landscape of taxation of non-U.S. operations and provides immediate deductions for certain new investments, among other provisions. Cintas’ effective tax rate for continuing operations was (69.5)% and 34.4% for the three months ended February 28, 2018 and 2017, respectively. For the nine months ended February 28, 2018 and 2017, Cintas' effective tax rate for continuing operations was 0.9% and 32.5%, respectively. The effective tax rate for the three and nine month periods ended February 28, 2018 were primarily impacted by the reduced U.S. corporate tax rate, which was partially offset by other provisions of the Tax Act, and resulted in a net favorable discrete provisional adjustment of $150.5 million related to the Tax Act. The net favorable discrete provisional adjustment is discussed in more detail in the following paragraphs. The three and nine month periods ended February 28, 2017 were also impacted by certain discrete items (primarily the tax accounting for stock-based compensation). In acknowledgment of the substantial changes incorporated in the U.S. Tax Reform, in conjunction with the timing of the enactment being just weeks before the majority of the provisions became effective, the SEC staff issued Staff Accounting Bulletin ("SAB") 118 to provide certain guidance in determining the accounting for income tax effects of the legislation in the accounting period of enactment as well as provide a measurement period within which to finalize and reflect such final effects associated with U.S. Tax Reform. During the three months ended February 28, 2018, enactment of the Tax Act resulted in the following provisional impacts on income tax expense: Provisional Deferred Tax Revaluation Cintas’ net deferred income taxes represent benefits that will be used to reduce corporate taxes expected to be paid as well as differences between the tax bases and carrying amounts of assets and liabilities that will result in taxable or deductible amounts in future years. Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in years in which those temporary differences are expected to be recovered or settled. As changes in tax laws or rates occur, deferred tax assets and liabilities are adjusted through income tax expense in the period changes are enacted. Upon enactment of the Tax Act, Cintas revalued its deferred tax assets and liabilities based on the rates at which they are expected to reverse in future periods (primarily at the newly enacted 21% U.S. corporate tax rate). Cintas will continue to revise certain aspects of the calculation, which could potentially affect the measurement of these balances or give rise to new deferred tax amounts. The provisional amount related to the revaluation of the net deferred tax liability balance was a benefit of $163.8 million, which was recognized as a component of income tax expense for the three months ended February 28, 2018. Provisional Transition Tax The one-time transition tax is based on Cintas’ post 1986 earnings and profits (E&P) of foreign subsidiaries that were previously deferred for U.S. Income tax purposes. Cintas recorded a provisional transition tax liability, net of foreign tax credits, of $9.5 million that was recognized as additional income tax expense during the three months ended February 28, 2018. Cintas is still revising the transition tax calculation, and this amount is subject to change based on computation of final fiscal 2018 E&P and the amounts held in cash and cash equivalents at the end of fiscal 2018. Provisional Foreign Withholding Tax Foreign withholding taxes of $3.8 million have been recognized on certain non-U.S. earnings subject to repatriation that were previously tax deferred. This is a provisional estimate and may change based on final E&P computations through fiscal 2018. We will continue to monitor those earnings we believe to be permanently reinvested in foreign operations, if any. As of February 28, 2018, the estimated impacts of the Tax Act recorded during the three months ended February 28, 2018 are provisional in nature. Cintas will continue to assess the impact of the Tax Act and will record adjustments through the income tax provision in the relevant period as amounts are known and reasonably estimable during the measurement period. As Cintas has not completed the final analysis of the tax impact of the Tax Act, the impact of the Tax Act may differ from Cintas’ quarterly provisional estimates due to information currently unavailable, changes in interpretations, the issuance of additional guidance and changes in assumptions, including actions Cintas may take in future periods as a result of the Tax Act. However, Cintas has recognized a reasonable estimate of the effects of the Tax Act on its deferred tax balances, the one-time transition tax and the withholding taxes related to foreign cash distributions within the consolidated condensed financial statements for the three months ending February 28, 2018. Given the effective date of the U.S. corporate tax rate reduction in the Tax Act, Cintas’ statutory federal corporate tax rate for fiscal 2018 will be a blended rate of 29.17% and will decline to 21% for fiscal 2019 and beyond.

Income Taxes

In the normal course of business, Cintas provides for uncertain tax positions and the related interest and adjusts its unrecognized tax benefits and accrued interest accordingly. As of February 28, 2018 and May 31, 2017, recorded unrecognized tax benefits were $18.5 million and $12.6 million, respectively, and are included in long-term accrued liabilities on the consolidated condensed balance sheet. The increase in the liability for the nine months ended February 28, 2018 is primarily related to an adjustment to the preliminary purchase price allocation for the G&K acquisition.

All U.S. federal income tax returns are closed to audit through fiscal 2014. Cintas is currently in various audits in certain foreign jurisdictions and certain domestic states. The years under foreign and domestic state audits cover fiscal years back to 2013. Based on the resolution of the various audits and other potential regulatory developments, it is reasonably possible that the balance of unrecognized tax benefits would not change for the fiscal year ending May 31, 2018.

The majority of Cintas' operations are in North America. Cintas is required to file federal income tax returns, as well as state income tax returns in a majority of the domestic states and also in certain Canadian provinces. At times, Cintas is subject to audits in these jurisdictions. The audits, by nature, are sometimes complex and can require several years to resolve. The final resolution of any such tax audit could result in either a reduction in Cintas' accruals or an increase in its income tax provision, either of which could have an impact on the consolidated condensed results of operations in any given period.

On December 22, 2017, the President signed into legislation the Tax Cuts and Jobs Act (the Tax Act). Among other changes, the Tax Act reduces the U.S. corporate tax rate from 35% to 21% and requires companies to pay a one-time transition tax on earnings of foreign subsidiaries. The Tax Act also includes provisions that are expected to offset some of the benefit of the U.S. corporate tax rate reduction, including the repeal of the deduction for domestic production activities and the expansion of the limitation on the deduction of certain executive compensation. In addition, the Tax Act alters the landscape of taxation of non-U.S. operations and provides immediate deductions for certain new investments, among other provisions.

Cintas’ effective tax rate for continuing operations was (69.5)% and 34.4% for the three months ended February 28, 2018 and 2017, respectively. For the nine months ended February 28, 2018 and 2017, Cintas' effective tax rate for continuing operations was 0.9% and 32.5%, respectively. The effective tax rate for the three and nine month periods ended February 28, 2018 were primarily impacted by the reduced U.S. corporate tax rate, which was partially offset by other provisions of the Tax Act, and resulted in a net favorable discrete provisional adjustment of $150.5 million related to the Tax Act. The net favorable discrete provisional adjustment is discussed in more detail in the following paragraphs. The three and nine month periods ended February 28, 2017 were also impacted by certain discrete items (primarily the tax accounting for stock-based compensation).

In acknowledgment of the substantial changes incorporated in the U.S. Tax Reform, in conjunction with the timing of the enactment being just weeks before the majority of the provisions became effective, the SEC staff issued Staff Accounting Bulletin ("SAB") 118 to provide certain guidance in determining the accounting for income tax effects of the legislation in the accounting period of enactment as well as provide a measurement period within which to finalize and reflect such final effects associated with U.S. Tax Reform. During the three months ended February 28, 2018, enactment of the Tax Act resulted in the following provisional impacts on income tax expense:

Provisional Deferred Tax Revaluation

Cintas’ net deferred income taxes represent benefits that will be used to reduce corporate taxes expected to be paid as well as differences between the tax bases and carrying amounts of assets and liabilities that will result in taxable or deductible amounts in future years. Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in years in which those temporary differences are expected to be recovered or settled. As changes in tax laws or rates occur, deferred tax assets and liabilities are adjusted through income tax expense in the period changes are enacted.

Upon enactment of the Tax Act, Cintas revalued its deferred tax assets and liabilities based on the rates at which they are expected to reverse in future periods (primarily at the newly enacted 21% U.S. corporate tax rate). Cintas will continue to revise certain aspects of the calculation, which could potentially affect the measurement of these balances or give rise to new deferred tax amounts. The provisional amount related to the revaluation of the net deferred tax liability balance was a benefit of $163.8 million, which was recognized as a component of income tax expense for the three months ended February 28, 2018.

Provisional Transition Tax

The one-time transition tax is based on Cintas’ post 1986 earnings and profits (E&P) of foreign subsidiaries that were previously deferred for U.S. Income tax purposes. Cintas recorded a provisional transition tax liability, net of foreign tax credits, of $9.5 million that was recognized as additional income tax expense during the three months ended February 28, 2018. Cintas is still revising the transition tax calculation, and this amount is subject to change based on computation of final fiscal 2018 E&P and the amounts held in cash and cash equivalents at the end of fiscal 2018.

Provisional Foreign Withholding Tax

Foreign withholding taxes of $3.8 million have been recognized on certain non-U.S. earnings subject to repatriation that were previously tax deferred. This is a provisional estimate and may change based on final E&P computations through fiscal 2018. We will continue to monitor those earnings we believe to be permanently reinvested in foreign operations, if any.

As of February 28, 2018, the estimated impacts of the Tax Act recorded during the three months ended February 28, 2018 are provisional in nature. Cintas will continue to assess the impact of the Tax Act and will record adjustments through the income tax provision in the relevant period as amounts are known and reasonably estimable during the measurement period. As Cintas has not completed the final analysis of the tax impact of the Tax Act, the impact of the Tax Act may differ from Cintas’ quarterly provisional estimates due to information currently unavailable, changes in interpretations, the issuance of additional guidance and changes in assumptions, including actions Cintas may take in future periods as a result of the Tax Act. However, Cintas has recognized a reasonable estimate of the effects of the Tax Act on its deferred tax balances, the one-time transition tax and the withholding taxes related to foreign cash distributions within the consolidated condensed financial statements for the three months ending February 28, 2018.

Given the effective date of the U.S. corporate tax rate reduction in the Tax Act, Cintas’ statutory federal corporate tax rate for fiscal 2018 will be a blended rate of 29.17% and will decline to 21% for fiscal 2019 and beyond.