Accounting Policies (Policies)	3 Months Ended
Accounting Policies (Policies)	Mar. 30, 2019
Accounting Policies [Abstract]
Basis of presentation	Basis of presentation The unaudited interim financial information of Kellogg Company (the Company) included in this report reflects all adjustments, all of which are of a normal and recurring nature, that management believes are necessary for a fair statement of the results of operations, comprehensive income, financial position, equity and cash flows for the periods presented. This interim information should be read in conjunction with the financial statements and accompanying footnotes within the Company’s 2018 Annual Report on Form 10-K. The condensed balance sheet information at December 29, 2018 was derived from audited financial statements, but does not include all disclosures required by accounting principles generally accepted in the United States. The results of operations for the quarterly period ended March 30, 2019 are not necessarily indicative of the results to be expected for other interim periods or the full year.
Accounts payable	Accounts payable The Company has agreements with certain third parties to provide accounts payable tracking systems which facilitates participating suppliers’ ability to monitor and, if elected, sell payment obligations from the Company to designated third-party financial institutions. Participating suppliers may, at their sole discretion, make offers to sell one or more payment obligations of the Company prior to their scheduled due dates at a discounted price to participating financial institutions. The Company’s goal in entering into these agreements is to capture overall supplier savings, in the form of payment terms or vendor funding, created by facilitating suppliers’ ability to sell payment obligations, while providing them with greater working capital flexibility. We have no economic interest in the sale of these suppliers’ receivables and no direct financial relationship with the financial institutions concerning these services. The Company’s obligations to its suppliers, including amounts due and scheduled payment dates, are not impacted by suppliers’ decisions to sell amounts under these arrangements. However, the Company’s right to offset balances due from suppliers against payment obligations is restricted by this agreement for those payment obligations that have been sold by suppliers.
New accounting standards adopted and accounting standards to be adopted in future periods	New accounting standards adopted in the period Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income. In February 2018, the Financial Accounting Standards Board (FASB) issued an Accounting Standard Update (ASU) permitting a company to reclassify the disproportionate income tax effects of the Tax Cuts and Jobs Act of 2017 on items within accumulated other comprehensive income (AOCI) to retained earnings. We elected to adopt the ASU effective in the first quarter of 2019 and reclassified the disproportionate income tax effect recorded within AOCI to retained earnings. This resulted in a decrease to AOCI and an increase to retained earnings of $22 million. The adjustment primarily related to deferred taxes previously recorded for pension and other postretirement benefits, as well as hedging positions for debt and net investment hedges. Leases. In February 2016, the FASB issued an ASU requiring the recognition of lease assets and lease liabilities by lessees for all leases with terms greater than 12 months. The distinction between finance leases and operating leases remains, with similar classification criteria as current GAAP to distinguish between capital and operating leases. The principal difference from prior guidance is that the lease assets and lease liabilities arising from operating leases will be recognized on the Consolidated Balance Sheet. The ASU is effective for fiscal years, and interim periods within those years, beginning after December 15, 2018 and was adopted in the first quarter of 2019. The Company adopted the ASU in the first quarter of 2019, using the optional transition method that allows for a cumulative-effect adjustment in the period of adoption with no restatement of prior periods. The Company elected the package of practical expedients permitted under the transition guidance that allows for the carry forward of historical lease classifications and consistent treatment of initial direct costs for existing leases. The Company also elected to apply the practical expedient that allows the continued historical treatment of land easements. The Company did not elect the practical expedient for the use of hindsight in evaluating the expected lease term of existing leases. The adoption of the ASU resulted in the recording of operating lease assets and operating lease liabilities of approximately $453 million and $461 million, respectively, as of December 30, 2018. The difference between the additional lease assets and lease liabilities, represents existing deferred rent and prepaid lease balances that were reclassified on the balance sheet. The adoption of the ASU did not have a material impact to the Company’s Consolidated Statements of Income or Cash Flows. Accounting standards to be adopted in future periods Cloud Computing Arrangements. In August 2018, the FASB issued ASU 2018-15: Intangibles - Goodwill and Other - Internal-Use Software: Customer's Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement that is a Service Contract. The ASU allows companies to capitalize implementation costs incurred in a hosting arrangement that is a service contract over the term of the hosting arrangement, including periods covered by renewal options that are reasonably certain to be exercised. The ASU is effective for fiscal years, and interim periods within those years, beginning after December 15, 2019 and can be applied retrospectively or prospectively. Early adoption is permitted. The Company is currently assessing when to adopt the ASU and the impact of adoption.