Equity Changes in Comprehensive Income (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 30, 2017	Dec. 31, 2016	Jan. 02, 2016
Equity [Abstract]
Net income	$ 1,269	$ 695	$ 614
Foreign currency translation adjustment before tax	(34)	(230)	(170)
Foreign currency translation adjustments tax (expense) benefit	113	(24)	(26)
Foreign currency translation adjustments after tax	79	(254)	(196)
Unrealized gain (loss) on cash flow hedges, pre-tax	0	(55)	8
Unrealized gain (loss) on cash flow hedges, tax (expense) benefit	0	22	(3)
Unrealized gain (loss) on cash flow hedges, after-tax	0	(33)	5
Reclassifications to net income, pre-tax	9	11	(23)
Reclassifications to net income, tax (expense) benefit	(3)	(6)	3
Reclassification to net income, after-tax	6	5	(20)
Net experience gain (loss)	44	25	0
Net experience gain (loss), tax (expense) benefit	(12)	(9)	0
Net experience gain (loss), after tax	32	16	0
Prior service credit (cost)	0	(4)	63
Prior service credit (cost), tax (expense) benefit	0	2	(24)
Prior service credit (cost), after-tax	0	(2)	39
Net experience loss, pre-tax	0	3	3
Net experience loss, tax (expense) benefit	0	(1)	(1)
Net experience loss, after-tax	0	2	2
Prior service cost	1	5	9
Prior service cost, tax (expense) benefit	0	(1)	(3)
Prior service cost, after-tax	1	4	6
Venezuela deconsolidation loss, pre-tax	0	63	0
Venezuela deconsolidation loss, tax (expense) benefit	0	0	0
Venezuela deconsolidation loss related to CTA, net of tax	0	63	0
Other Comprehensive Income (Loss), before Tax	20	(182)	(110)
Other Comprehensive Income (Loss), Tax	98	(17)	(54)
Other Comprehensive Income (loss)	118	(199)	(164)
Comprehensive income	1,387	496	450
Net income (loss) attributable to noncontrolling interests	0	1	0
Other comprehensive income (loss) attributable to noncontrolling interests	0	0	(1)
Comprehensive income attributable to Kellogg Company	$ 1,387	$ 495	$ 451