Consolidated Statement of Comprehensive Income (Unaudited) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jul. 02, 2022	Jul. 03, 2021	Jul. 02, 2022	Jul. 03, 2021
Statement of Comprehensive Income [Abstract]
Net income	$ 326	$ 385	$ 750	$ 756
Other comprehensive income (loss), pre-tax:
Foreign currency translation adjustments, pre-tax	(243)	50	(260)	(47)
Net investment hedges, pre-tax
Net investment hedge gain (loss), pre-tax	255	(42)	356	88
Cash flow hedges, pre-tax:
Unrealized gain (loss) on cash flow hedges, pre-tax	74	(39)	151	39
Reclassification to net income, pre-tax	4	10	8	15
Postretirement and postemployment benefits reclassification to net income, pre-tax:
Net experience (gain) loss	(1)	(1)	(2)	(2)
Available-for-sale securities, pre-tax
Unrealized gain (loss) on available-for-sale securities, pre-tax	(1)	1	(4)	(1)
Other comprehensive income (loss), pre-tax	88	(21)	249	92
Other comprehensive income (loss), tax (expense) benefit
Foreign currency translation adjustments, tax (expense) benefit	1	0	2	0
Net investment hedges, tax (expense) benefit
Net investment hedge gain (loss), tax (expense) benefit	(67)	11	(94)	(23)
Cash flow hedges, tax (expense) benefit:
Unrealized gain (loss) on cash flow hedges, tax (expense) benefit	(20)	11	(40)	(10)
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), Reclassification, Tax	(1)	(3)	(2)	(4)
Postretirement and postemployment benefits reclassification to net income, tax (expense) benefit:
Net experience loss, tax (expense) benefit	1	1	1	1
Available-for-sale securities, tax (expense) benefit
Unrealized gain (loss) on available-for-sale securities, tax (expense) benefit	0	0	0	0
Other comprehensive income (loss), tax (expense) benefit	(86)	20	(133)	(36)
Other comprehensive income (loss), after tax:
Foreign currency translation adjustments, after-tax	(242)	50	(258)	(47)
Net investment hedges, after tax
Net investment hedge gain (loss), after-tax	188	(31)	262	65
Cash flow hedges, after tax
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), before Reclassification, after Tax	54	(28)	111	29
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), Reclassification, after Tax	3	7	6	11
Postretirement and postemployment benefits reclassification to net income, after-tax:
Net experience (gain) loss, after-tax	0	0	(1)	(1)
Available-for-sale securities, after tax
Unrealized gain (loss) on available-for-sale securities, after-tax	(1)	1	(4)	(1)
Other comprehensive income (loss)	2	(1)	116	56
Comprehensive income	328	384	866	812
Net income attributable to noncontrolling interests	0	5	2	8
Other comprehensive income (loss) attributable to noncontrolling interests	(8)	(3)	(4)	(13)
Comprehensive income attributable to Kellogg Company	$ 336	$ 382	$ 868	$ 817