Equity Schedule of Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ 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
Equity [Abstract]
Net income (loss) attributable to Kellogg Company, Basic	$ (53)	$ 292	$ 280	$ 175	$ (41)	$ 205	$ 223	$ 227	$ 694	$ 614	$ 632
Average shares outstanding, Basic (in shares)									350	354	358
Earnings per share, Basic (in shares)	$ (0.15)	$ 0.83	$ 0.80	$ 0.50	$ (0.12)	$ 0.58	$ 0.63	$ 0.64	$ 1.98	$ 1.74	$ 1.76
Average shares outstanding, Dilutive potential common shares (in shares)									4	2	2
Earnings per share, Dilutive potential common shares (in dollars per share)									$ (0.02)	$ (0.02)	$ (0.01)
Net income attributed to Kellogg Company, Diluted									$ 694	$ 614	$ 632
Average shares outstanding, Diluted (in shares)									354	356	360
Earnings per share, Diluted (in dollars per share)	$ (0.15)	$ 0.82	$ 0.79	$ 0.49	$ (0.12)	$ 0.58	$ 0.63	$ 0.64	$ 1.96	$ 1.72	$ 1.75