Sale of Accounts Receivable - Narrative (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2018	Dec. 30, 2017	Jul. 31, 2016
Receivables Sales Agreement
Transfer of Financial Assets Accounted for as Sales [Line Items]
Gain (Loss) on Sale of Accounts Receivable	$ (7)
Receivables Sales Agreement | Maximum [Member]
Transfer of Financial Assets Accounted for as Sales [Line Items]
Transfers of Accounts Receivable Agreements	988	$ 800
Receivables Sales Agreement | Sold And Outstanding
Transfer of Financial Assets Accounted for as Sales [Line Items]
Transfer of Financial Assets Accounted for as Sales, Amount Derecognized	927	601
Kellogg Funding Company Program
Transfer of Financial Assets Accounted for as Sales [Line Items]
Cash Proceeds Received for Assets Derecognized		412
Deferred Purchase Price	21	21
Kellogg Funding Company Program | Maximum [Member]
Transfer of Financial Assets Accounted for as Sales [Line Items]
Transfers of Accounts Receivable Agreements			$ 600
Kellogg Funding Company Program | Sold And Outstanding
Transfer of Financial Assets Accounted for as Sales [Line Items]
Transfer of Financial Assets Accounted for as Sales, Amount Derecognized		433
Kellogg Foreign Subsidiaries Other Program
Transfer of Financial Assets Accounted for as Sales [Line Items]
Transfers of Accounts Receivable Agreements	$ 43	$ 86