Sale of Accounts Receivable - Narrative (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended	12 Months Ended
	Jul. 01, 2017	Jul. 01, 2017	Dec. 31, 2016	Jul. 31, 2016	Jul. 02, 2016
Receivables Sales Agreement
Transfer of Financial Assets Accounted for as Sales [Line Items]
Gain (Loss) on Sale of Accounts Receivable	$ (3)	$ (5)
Receivables Sales Agreement | Maximum
Transfer of Financial Assets Accounted for as Sales [Line Items]
Transfers of Accounts Receivable Agreements	700	700
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	655	655	$ 562
Receivables Sales Agreement | Sold Since Inception
Transfer of Financial Assets Accounted for as Sales [Line Items]
Transfer of Financial Assets Accounted for as Sales, Amount Derecognized	1,100	1,100			$ 529
Kellogg Funding Company Program
Transfer of Financial Assets Accounted for as Sales [Line Items]
Gain (Loss) on Sale of Accounts Receivable	(2)	(3)
Cash Proceeds Received for Assets Derecognized	404	404	255
Deferred Purchase Price		39	37
Kellogg Funding Company Program | Maximum
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	443	443
Kellogg Funding Company Program | Sold Since Inception
Transfer of Financial Assets Accounted for as Sales [Line Items]
Transfer of Financial Assets Accounted for as Sales, Amount Derecognized	1,300	1,300	292
Kellogg Foreign Subsidiaries Other Program
Transfer of Financial Assets Accounted for as Sales [Line Items]
Transfers of Accounts Receivable Agreements	35	35	$ 124
Transfer of Financial Assets Accounted for as Sales, Amount Derecognized	$ 94	$ 94