Consolidated Statement of Comprehensive Income (unaudited) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jul. 01, 2023	Jul. 02, 2022	Jul. 01, 2023	Jul. 02, 2022
Statement of Comprehensive Income [Abstract]
Net income	$ 362	$ 326	$ 664	$ 750
Other comprehensive income (loss), pre-tax:
Foreign currency translation adjustments, pre-tax	(383)	(243)	(341)	(260)
Net investment hedges, pre-tax
Net investment hedge gain (loss), pre-tax	(37)	255	(94)	356
Cash flow hedges, pre-tax:
Net deferred gain (loss) on cash flow hedges, pre-tax	15	74	(3)	151
Reclassification to net income, pre-tax	2	4	5	8
Postretirement and postemployment benefits reclassification to net income, pre-tax:
Net experience (gain) loss	0	(1)	(1)	(2)
Available-for-sale securities, pre-tax
Unrealized gain (loss) on available-for-sale securities, pre-tax	0	(1)	1	(4)
Other comprehensive income (loss), pre-tax	(403)	88	(433)	249
Other comprehensive income (loss), tax (expense) benefit
Foreign currency translation adjustments, tax (expense) benefit	(1)	1	2	2
Net investment hedges, tax (expense) benefit
Net investment hedge gain (loss), tax (expense) benefit	7	(67)	22	(94)
Cash flow hedges, tax (expense) benefit:
Net deferred gain (loss) on cash flow hedges, tax (expense) benefit	(4)	(20)	1	(40)
Reclassification to net income, tax (expense) benefit	0	(1)	(1)	(2)
Postretirement and postemployment benefits reclassification to net income, tax (expense) benefit:
Net experience loss, tax (expense) benefit	0	1	0	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	2	(86)	24	(133)
Other comprehensive income (loss), after tax:
Foreign currency translation adjustments, after-tax	(384)	(242)	(339)	(258)
Net investment hedges, after tax
Net investment hedge gain (loss), after-tax	(30)	188	(72)	262
Cash flow hedges, after tax
Net deferred gain (loss) on cash flow hedges	11	54	(2)	111
Reclassification to net income, after tax	2	3	4	6
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	0	(1)	1	(4)
Other comprehensive income (loss)	(401)	2	(409)	116
Comprehensive income	(39)	328	255	866
Net income attributable to noncontrolling interests	5	0	9	2
Other comprehensive income (loss) attributable to noncontrolling interests	(171)	(8)	(174)	(4)
Comprehensive income attributable to Kellogg Company	$ 127	$ 336	$ 420	$ 868