LONG-TERM DEBT (Callable Notes) (Details) (USD $) In Millions, unless otherwise specified	Feb. 24, 2013	May 27, 2012	Feb. 24, 2013 Ralcorp 5.93% senior notes (Series J) due May 2022	Feb. 24, 2013 Ralcorp 7.6% senior notes (Series 2009B) due May 2021	Feb. 24, 2013 Ralcorp 5.56% senior notes (Series I, Tranche A) due January 2019	Feb. 24, 2013 Ralcorp 5.58% senior notes (Series I, Tranche B) due January 2019	Feb. 24, 2013 Ralcorp 7.45% senior notes (Series 2009A) due May 2019	Feb. 24, 2013 Ralcorp 5.57% senior notes (Series E) due December 2015	Feb. 24, 2013 Ralcorp 5.43% senior notes (Series C) due December 2013	Feb. 24, 2013 Ralcorp 4.76% senior notes (Series D) due December 2013	Feb. 24, 2013 Ralcorp Callable Notes [Member]	May 27, 2012 Ralcorp Callable Notes [Member]	Feb. 24, 2013 Ralcorp [Member] Ralcorp Callable Notes [Member]	Feb. 28, 2013 Ralcorp [Member] Subsequent Event [Member] Ralcorp 5.93% senior notes (Series J) due May 2022	Feb. 28, 2013 Ralcorp [Member] Subsequent Event [Member] Ralcorp 7.6% senior notes (Series 2009B) due May 2021	Feb. 28, 2013 Ralcorp [Member] Subsequent Event [Member] Ralcorp 5.56% senior notes (Series I, Tranche A) due January 2019	Feb. 28, 2013 Ralcorp [Member] Subsequent Event [Member] Ralcorp 5.58% senior notes (Series I, Tranche B) due January 2019	Feb. 28, 2013 Ralcorp [Member] Subsequent Event [Member] Ralcorp 7.45% senior notes (Series 2009A) due May 2019	Feb. 28, 2013 Ralcorp [Member] Subsequent Event [Member] Ralcorp 5.57% senior notes (Series E) due December 2015	Feb. 28, 2013 Ralcorp [Member] Subsequent Event [Member] Ralcorp 5.43% senior notes (Series C) due December 2013	Feb. 28, 2013 Ralcorp [Member] Subsequent Event [Member] Ralcorp 4.76% senior notes (Series D) due December 2013	Feb. 28, 2013 Ralcorp [Member] Subsequent Event [Member] Ralcorp Callable Notes [Member]
Debt Instrument [Line Items]
Interest rate	3.25%		5.93%	7.60%	5.56%	5.58%	7.45%	5.57%	5.43%	4.76%
Senior notes	$ 10,351.0	$ 2,938.8									$ 460.7	$ 0	$ 0	$ 100.0	$ 50.0	$ 75.0	$ 25.0	$ 50.0	$ 100.0	$ 50.0	$ 10.7	$ 460.7