Quarterly Financial Data Net income and earnings per share (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	Jan. 02, 2016	Oct. 03, 2015	Jul. 04, 2015	Apr. 04, 2015	Jan. 03, 2015	Sep. 27, 2014	Jun. 28, 2014	Mar. 29, 2014	Jan. 02, 2016	Jan. 03, 2015	Dec. 28, 2013
Quarterly Financial Information Disclosure [Abstract]
Net income (loss) attributable to Kellogg Company, Basic	$ (41)	$ 205	$ 223	$ 227	$ (293)	$ 224	$ 295	$ 406	$ 614	$ 632	$ 1,807
Basic	$ (0.12)	$ 0.58	$ 0.63	$ 0.64	$ (0.82)	$ 0.63	$ 0.82	$ 1.13	$ 1.74	$ 1.76	$ 4.98
Diluted	$ (0.12)	$ 0.58	$ 0.63	$ 0.64	$ (0.82)	$ 0.62	$ 0.82	$ 1.12	$ 1.72	$ 1.75	$ 4.94