Quarterly Financial Data Net income and earnings per share (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Oct. 01, 2016	Jul. 02, 2016	Apr. 02, 2016	Jan. 02, 2016	Oct. 03, 2015	Jul. 04, 2015	Apr. 04, 2015	Dec. 31, 2016	Jan. 02, 2016	Jan. 03, 2015
Quarterly Financial Information Disclosure [Abstract]
Net income (loss) attributable to Kellogg Company, Basic	$ (53)	$ 292	$ 280	$ 175	$ (41)	$ 205	$ 223	$ 227	$ 694	$ 614	$ 632
Basic	$ (0.15)	$ 0.83	$ 0.80	$ 0.50	$ (0.12)	$ 0.58	$ 0.63	$ 0.64	$ 1.98	$ 1.74	$ 1.76
Diluted	$ (0.15)	$ 0.82	$ 0.79	$ 0.49	$ (0.12)	$ 0.58	$ 0.63	$ 0.64	$ 1.96	$ 1.72	$ 1.75