Sale of Accounts Receivable (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 29, 2018	Dec. 30, 2017	Dec. 31, 2016
Monetization Program
Transfer of Financial Assets Accounted for as Sales [Line Items]
Gain (Loss) on Sale of Accounts Receivable	$ (26)	$ (11)	$ (5)
Monetization Program | Maximum
Transfer of Financial Assets Accounted for as Sales [Line Items]
Transfers Of Accounts Receivable Agreements	1,033
Monetization Program | Sold And Outstanding
Transfer of Financial Assets Accounted for as Sales [Line Items]
Transfer of Accounts Receivable Agreements	900	601
SecuritizationProgram [Member]
Transfer of Financial Assets Accounted for as Sales [Line Items]
Transfer of Accounts Receivable Agreements		412
Gain (Loss) on Sale of Accounts Receivable		(7)
Deferred Purchase Price	21
SecuritizationProgram [Member] | Maximum
Transfer of Financial Assets Accounted for as Sales [Line Items]
Transfers Of Accounts Receivable Agreements		600
SecuritizationProgram [Member] | Sold And Outstanding
Transfer of Financial Assets Accounted for as Sales [Line Items]
Transfer of Accounts Receivable Agreements		433
Kellogg Foreign Subsidiaries Program | Sold And Outstanding
Transfer of Financial Assets Accounted for as Sales [Line Items]
Transfer of Accounts Receivable Agreements	$ 93	$ 86