Consolidated Statement of Comprehensive Income (Unaudited) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Oct. 01, 2022	Sep. 30, 2023	Oct. 01, 2022
Statement of Comprehensive Income [Abstract]
Net income	$ 270	$ 312	$ 934	$ 1,062
Other comprehensive income (loss), pre-tax:
Foreign currency translation adjustments, pre-tax	(134)	(249)	(475)	(509)
Net investment hedges, pre-tax
Net investment hedge gain (loss), pre-tax	111	260	17	616
Cash flow hedges, pre-tax:
Net deferred gain (loss) on cash flow hedges, pre-tax	40	62	37	213
Reclassification to net income, pre-tax	2	(14)	7	(6)
Postretirement and postemployment benefits reclassification to net income, pre-tax:
Net experience (gain) loss	(1)	0	(2)	(2)
Available-for-sale securities, pre-tax
Unrealized gain (loss) on available-for-sale securities, pre-tax	(1)	(2)	0	(6)
Reclassification to net income on available-for-sale securities, pre-tax	1	1	1	1
Other comprehensive income (loss), pre-tax	18	58	(415)	307
Other comprehensive income (loss), tax (expense) benefit
Foreign currency translation adjustments, tax (expense) benefit	1	4	3	6
Net investment hedges, tax (expense) benefit
Net investment hedge gain (loss), tax (expense) benefit	(26)	(68)	(4)	(162)
Cash flow hedges, tax (expense) benefit:
Net deferred gain (loss) on cash flow hedges, tax (expense) benefit	(10)	(16)	(9)	(56)
Reclassification to net income, tax (expense) benefit	(1)	3	(2)	1
Postretirement and postemployment benefits reclassification to net income, tax (expense) benefit:
Net experience loss, tax (expense) benefit	0	0	0	1
Available-for-sale securities, tax (expense) benefit
Unrealized gain (loss) on available-for-sale securities, tax (expense) benefit	0	0	0	0
Reclassification to net income on available for sale of securities, tax (expense) benefit	0	0	0	0
Other comprehensive income (loss), tax (expense) benefit	(36)	(77)	(12)	(210)
Other comprehensive income (loss), after tax:
Foreign currency translation adjustments, after-tax	(133)	(245)	(472)	(503)
Net investment hedges, after tax
Net investment hedge gain (loss), after-tax	85	192	13	454
Cash flow hedges, after tax
Net deferred gain (loss) on cash flow hedges	30	46	28	157
Reclassification to net income, after tax	1	(11)	5	(5)
Postretirement and postemployment benefits reclassification to net income, after-tax:
Net experience (gain) loss, after-tax	(1)	0	(2)	(1)
Available-for-sale securities, after tax
Unrealized gain (loss) on available-for-sale securities, after-tax	(1)	(2)	0	(6)
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Sale of Securities, Net of Tax	1	1	1	1
Other comprehensive income (loss)	(18)	(19)	(427)	97
Comprehensive income	252	293	507	1,159
Net income attributable to noncontrolling interests	1	2	10	4
Other comprehensive income (loss) attributable to noncontrolling interests	(7)	(22)	(181)	(26)
Comprehensive income attributable to Kellanova	$ 258	$ 313	$ 678	$ 1,181