Comprehensive Income Statement - USD ($) $ in Millions	12 Months Ended
	Jan. 01, 2022	Jan. 02, 2021	Dec. 28, 2019
Statement of Comprehensive Income [Abstract]
Net income	$ 1,495	$ 1,264	$ 977
Other comprehensive income (loss), pre-tax:
Foreign currency translation adjustment before tax	14	(405)	100
Cash flow hedges, pre-tax:
Unrealized gain (loss) on cash flow hedges, pre-tax	38	(9)	5
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), Reclassification, before Tax	22	14	4
Postretirement and postemployment benefit amounts arising during the period, pre-tax:
Net experience gain (loss)	(2)	(4)	(16)
Prior service credit (cost)	(18)	(21)	3
Postretirement and postemployment benefits reclassification to net income, pre-tax:
Net experience (gain) loss, pre-tax	(2)	(3)	(5)
Prior service (credit) cost, pre-tax	0	(1)	(1)
Available-for-sale securities, pre-tax
Unrealized gain (loss) on available-for-sale securities, pre-tax	(1)	3	4
Reclassification to net income on available-for-sale securities, pre-tax	(2)	0	(4)
Other comprehensive income (loss), pre-tax	49	(426)	90
Other comprehensive income (loss), tax (expense) benefit:
Foreign currency translation adjustments tax (expense) benefit	(57)	84	(19)
Cash flow hedges, tax (expense) benefit:
Unrealized gain (loss) on cash flow hedges	(10)	2	(1)
Reclassification to net income, tax (expense) benefit	(6)	(4)	(1)
Postretirement and postemployment benefit amounts arising during the period, tax (expense) benefit:
Net experience gain (loss), tax (expense) benefit	1	1	5
Prior service credit (cost), tax (expense) benefit	4	6	(1)
Postretirement and postemployment benefits reclassification to net income, tax (expense) benefit:
Net experience (gain) loss, tax (expense) benefit	0	1	1
Prior service (credit) cost, tax (expense) benefit	0	0	0
Available-for-sale securities, tax (expense) benefit
Unrealized gain (loss) on available-for-sale securities, tax (expense) benefit	0	0	0
Reclassification to net income on available-for-sale securities, tax (expense) benefit	0	0	0
Other comprehensive income (loss), tax (expense) benefit	(68)	90	(16)
Other comprehensive income (loss), after-tax
Foreign currency translation adjustments after tax	(43)	(321)	81
Cash flow hedges, after-tax:
Unrealized gain (loss) on cash flow hedges, after-tax	28	(7)	4
Reclassification to net income, after-tax	16	10	3
Postretirement and postemployment benefit amounts arising during the period, after-tax
Net experience gain (loss), after tax	(1)	(3)	(11)
Prior service credit (cost), after-tax	(14)	(15)	2
Postretirement and postemployment benefits reclassification to net income, after-tax
Net experience loss, after-tax	(2)	(2)	(4)
Prior service cost, after-tax	0	(1)	(1)
Available-for-sale securities, after-tax
Unrealized gain (loss) on available-for-sale securities, after-tax	(1)	3	4
Reclassification to net income on available-for-sale securities, after-tax	(2)	0	(4)
Other comprehensive income (loss)	(19)	(336)	74
Comprehensive income	1,476	928	1,051
Net income (loss) attributable to noncontrolling interests	7	13	17
Other comprehensive income (loss) attributable to noncontrolling interests	(30)	(52)	0
Comprehensive income attributable to Kellogg Company	$ 1,499	$ 967	$ 1,034