CONSOLIDATED STATEMENT OF COMPREHENSIVE INCOME (Unaudited) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 27, 2025	Sep. 28, 2024	Sep. 27, 2025	Sep. 28, 2024
Statement of Comprehensive Income [Abstract]
Net income	$ 314	$ 370	$ 925	$ 988
Other comprehensive income (loss), pre-tax:
Foreign currency translation adjustments during period, pre-tax	(22)	94	287	(256)
Net investment hedges, pre-tax
Net investment hedge gain (loss), pre-tax	5	(133)	(322)	(34)
Cash flow hedges, pre-tax:
Net deferred gain (loss) on cash flow hedges, pre-tax		0		39
Reclassification to net income, pre-tax	(1)	0	(4)	3
Postretirement and postemployment benefit amounts arising during the period, pre-tax:
Prior service (credit) cost, pre-tax		1		2
Postretirement and postemployment benefits reclassification to net income, pre-tax:
Net experience (gain) loss	(1)	(1)	(1)	(2)
Prior service (credit) cost, pre-tax	1		1
Other comprehensive income (loss), pre-tax	(18)	(39)	(39)	(248)
Other comprehensive income (loss), tax (expense) benefit
Foreign currency translation adjustments during period, tax (expense) benefit	(1)	0	(2)	0
Net investment hedges, tax (expense) benefit
Net investment hedge gain (loss), tax (expense) benefit	(1)	34	82	9
Cash flow hedges, tax (expense) benefit:
Net deferred gain (loss) on cash flow hedges, tax (expense) benefit		0		(10)
Reclassification to net income, tax (expense) benefit	0	0	1	(1)
Postretirement and postemployment benefit amounts arising during the period, tax (expense) benefit:
Prior service (credit) cost, tax (expense) benefit		0		0
Postretirement and postemployment benefits reclassification to net income, tax (expense) benefit:
Net experience loss, tax (expense) benefit	0	0	0	0
Prior service cost, tax (expense) benefit	0		0
Other comprehensive income (loss), tax (expense) benefit	(2)	34	81	(2)
Other comprehensive income (loss), after tax:
Foreign currency translation adjustments during period, after-tax	(23)	94	285	(256)
Net investment hedges, after tax
Net investment hedge gain (loss), after-tax	4	(99)	(240)	(25)
Cash flow hedges, after tax
Net deferred gain (loss) on cash flow hedges		0		29
Reclassification to net income, after tax	(1)	0	(3)	2
Postretirement and postemployment benefit amounts arising during the period, after-tax:
Prior service (credit) cost, after-tax		1		2
Postretirement and postemployment benefits reclassification to net income, after-tax:
Net experience (gain) loss, after-tax	(1)	(1)	(1)	(2)
Prior service cost, after-tax	1		1
Other comprehensive income (loss)	(20)	(5)	42	(250)
Comprehensive income	294	365	967	738
Net income (loss) attributable to noncontrolling interests	5	3	13	10
Other comprehensive income (loss) attributable to noncontrolling interests	(2)	(15)	2	(93)
Comprehensive income attributable to Kellanova	$ 291	$ 377	$ 952	$ 821