Equity - Schedule of Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jul. 04, 2015	Jun. 28, 2014	Jul. 04, 2015	Jun. 28, 2014
Equity [Abstract]
Net income attributable to Kellogg Company, Basic	$ 223	$ 295	$ 450	$ 701
Average shares outstanding, Basic (in shares)	353	359	354	360
Earnings per share, Basic (in dollars per share)	$ 0.63	$ 0.82	$ 1.27	$ 1.95
Average shares outstanding, Dilutive potential common shares (in shares)	2	3	2	2
Earnings per share, Dilutive potential common shares (in dollars per share)			$ (0.01)	$ (0.01)
Net income attributable to Kellogg Company, Diluted	$ 223	$ 295	$ 450	$ 701
Average shares outstanding, Diluted (in shares)	355	362	356	362
Earnings per share, Diluted (in dollars per share)	$ 0.63	$ 0.82	$ 1.26	$ 1.94