Consolidated Statement of Comprehensive Income (Unaudited) - USD ($) $ in Millions	3 Months Ended
	Apr. 02, 2022	Apr. 03, 2021
Statement of Comprehensive Income [Abstract]
Net income	$ 424	$ 371
Other comprehensive income (loss), pre-tax:
Foreign currency translation adjustments, pre-tax	84	33
Cash flow hedges, pre-tax:
Unrealized gain (loss) on cash flow hedges, pre-tax	77	78
Reclassification to net income, pre-tax	4	5
Postretirement and postemployment benefits reclassification to net income, pre-tax:
Net experience (gain) loss	(1)	(1)
Available-for-sale securities, pre-tax
Unrealized gain (loss) on available-for-sale securities, pre-tax	(3)	(2)
Other comprehensive income (loss), pre-tax	161	113
Other comprehensive income (loss), tax (expense) benefit
Foreign currency translation adjustments, tax (expense) benefit	(26)	(34)
Cash flow hedges, tax (expense) benefit:
Unrealized gain (loss) on cash flow hedges, tax (expense) benefit	(20)	(21)
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), Reclassification, Tax	(1)	(1)
Postretirement and postemployment benefits reclassification to net income, tax (expense) benefit:
Net experience loss, tax (expense) benefit	0	0
Available-for-sale securities, tax (expense) benefit
Unrealized gain (loss) on available-for-sale securities, tax (expense) benefit	0	0
Other comprehensive income (loss), tax (expense) benefit	(47)	(56)
Other comprehensive income (loss), after tax:
Foreign currency translation adjustments, after-tax	58	(1)
Cash flow hedges, after tax
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), before Reclassification, after Tax	57	57
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), Reclassification, after Tax	3	4
Postretirement and postemployment benefits reclassification to net income, after-tax:
Net experience (gain) loss, after-tax	(1)	(1)
Available-for-sale securities, after tax
Unrealized gain (loss) on available-for-sale securities, after-tax	(3)	(2)
Other comprehensive income (loss)	114	57
Comprehensive income	538	428
Net income attributable to noncontrolling interests	2	3
Other comprehensive income (loss) attributable to noncontrolling interests	4	(10)
Comprehensive income attributable to Kellogg Company	$ 532	$ 435