Consolidated Statement of Equity (Unaudited) - USD ($) shares in Millions, $ in Millions	Total	Common stock	Capital in excess of par value	Retained earnings	Treasury stock	Accumulated other comprehensive income (loss)	Total Kellogg Company equity	Non-controlling interests
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	$ 2,194
Balance at Dec. 30, 2017		$ 105	$ 878	$ 7,069	$ (4,417)	$ (1,457)	$ 2,178	$ 16
Balance (in shares) at Dec. 30, 2017		421			75
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	444			444			444
Dividends declared	(187)			(187)			(187)
Other comprehensive income (loss)	50					50	50
Stock compensation	16		16				16
Stock options exercised and other (in shares)					(1)
Stock options exercised and other	37		(42)	8	$ 71		37
Balance (in shares) at Mar. 31, 2018		421			74
Balance at Mar. 31, 2018		$ 105	852	7,334	$ (4,346)	(1,407)	2,538	16
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	2,554
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	3,159
Balance at Dec. 29, 2018	2,601	$ 105	895	7,652	$ (4,551)	(1,500)	2,601	558
Balance (in shares) at Dec. 29, 2018		421			77
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock repurchases (in shares)					4
Common stock repurchases	(220)				$ (220)		(220)
Net income	285			282			282	3
Dividends declared	(192)			(192)			(192)
Other comprehensive income (loss)	58					55	55	3
Reclassification of tax effects relating to U.S. tax reform	0			22		(22)	0
Stock compensation	13		13				13
Stock options exercised and other (in shares)					(1)
Stock options exercised and other	(6)		(31)	(2)	$ 27		(6)
Balance (in shares) at Mar. 30, 2019		421			80
Balance at Mar. 30, 2019	2,533	$ 105	$ 877	$ 7,762	$ (4,744)	$ (1,467)	$ 2,533	$ 564
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	$ 3,097