Asset Impairment Charges and Exit Costs (Narrative) (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	6 Months Ended		12 Months Ended			1 Months Ended	3 Months Ended	6 Months Ended		3 Months Ended		6 Months Ended	12 Months Ended	3 Months Ended		6 Months Ended	12 Months Ended
	Dec. 31, 2012 employee	Dec. 31, 2011	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2010	Dec. 31, 2012 Gruma S.A.B. de C.V. [Member]	Sep. 30, 2012 Gruma S.A.B. de C.V. [Member]	Dec. 31, 2012 Gruma S.A.B. de C.V. [Member]	Dec. 31, 2012 Agricultural Services [Member]	Mar. 31, 2012 Corporate [Member]	Dec. 31, 2011 Corporate [Member]	Dec. 31, 2011 Corporate [Member]	Jun. 30, 2012 Corporate [Member]	Mar. 31, 2012 Corn Processing [Member]	Dec. 31, 2011 Corn Processing [Member]	Dec. 31, 2011 Corn Processing [Member]	Jun. 30, 2012 Corn Processing [Member]
Asset Impairment Charges And Exit Costs [Line Items]
Facility exit and other related costs	$ 146	$ 352	$ 366				$ 146		$ 146	$ 4	$ 13	$ 13	$ 17	$ 14	$ 339	$ 339	$ 349
Facility exit and other related costs, per share							$ 0.16
Foreign currency translation adjustment, before tax	371	(707)	(751)	859	(557)		123
Sales price of investment in affiliate						450
Potential consideration reciepts the Company could receive						60		60
Period of time potential consideration payments would be received, in months								42 months
Recovery of prior quarter facility exit and other related costs														4
Number of positions eliminated	1,200
Reduction in annual pre-tax expenses as a result of organizational resutrcturing	150
Remeasurement charge			$ 34