LONG-TERM DEBT (Schedule of Debt) (Details) (USD $) In Millions, unless otherwise specified	Feb. 24, 2013	May 27, 2012
Debt Instrument [Line Items]
Senior notes	$ 10,351.0	$ 2,938.8
Fair value adjustment of notes in connection with Ralcorp acquisition	263.2	0
Unamortized discounts/premiums	(60.0)	(59.8)
Adjustment due to hedging activity	10.8	17.7
Less current installments	(719.7)	(38.1)
Total long-term debt	9,845.3	2,858.6
Interest rate	3.25%
4.65% Senior Debt Due January 2043 [Member]
Debt Instrument [Line Items]
Senior notes	1,000.0	0
Interest rate	4.65%
6.625% Senior Debt Due August 2039 (Including Ralcorp Senior Notes) [Member]
Debt Instrument [Line Items]
Senior notes	450.0	0
Interest rate	6.625%
8.25% Senior Debt Due September 2039 [Member]
Debt Instrument [Line Items]
Senior notes	300.0	300.0
Interest rate	8.25%
7.0% Senior Debt Due October 2028 [Member]
Debt Instrument [Line Items]
Senior notes	382.2	382.2
Interest rate	7.00%
6.7% Senior Debt Due August 2027 [Member]
Debt Instrument [Line Items]
Senior notes	9.2	9.2
Interest rate	6.70%
7.125% Senior Debt Due October 2026 [Member]
Debt Instrument [Line Items]
Senior notes	372.4	372.4
Interest rate	7.125%
3.2% Senior Debt Due January 2023 [Member]
Debt Instrument [Line Items]
Senior notes	1,225.0	0
Interest rate	3.20%
3.25% Senior Debt Due September 2022 [Member]
Debt Instrument [Line Items]
Senior notes	250.0	0
Interest rate	3.25%
9.75% Subordinated Debt Due March 2021 [Member]
Debt Instrument [Line Items]
Senior notes	195.9	195.9
Interest rate	9.75%
4.95% Senior Debt Due August 2020 (Including Ralcorp Senior Notes) [Member]
Debt Instrument [Line Items]
Senior notes	300.0	0
Interest rate	4.95%
7.0% Senior Debt Due April 2019 [Member]
Debt Instrument [Line Items]
Senior notes	500.0	500.0
Interest rate	7.00%
1.9% Senior Debt Due January 2018 [Member]
Debt Instrument [Line Items]
Senior notes	1,000.0	0
Interest rate	1.90%
LIBOR plus 1.75% term loans due January 2018 [Member]
Debt Instrument [Line Items]
Senior notes	1,500.0	0
Interest rate	1.75%
2.1% Senior Debt Due March 2018 [Member]
Debt Instrument [Line Items]
Senior notes	250.0	0
Interest rate	2.10%
5.819% Senior Debt Due June 2017 [Member]
Debt Instrument [Line Items]
Senior notes	500.0	500.0
Interest rate	5.819%
1.3% Senior Debt Due January 2016 [Member]
Debt Instrument [Line Items]
Senior notes	750.0	0
Interest rate	1.30%
1.35% Senior Debt Due September 2015 [Member]
Debt Instrument [Line Items]
Senior notes	250.0	0
Interest rate	1.35%
5.875% Senior Debt Due April 2014 [Member]
Debt Instrument [Line Items]
Senior notes	500.0	500.0
Interest rate	5.875%
Ralcorp Callable Notes (prepaid subsequent to February 24, 2013)
Debt Instrument [Line Items]
Senior notes	460.7	0
2.00% to 9.59% Lease Financing Obligations Due Through 2029 [Member]
Debt Instrument [Line Items]
Senior notes	77.3	106.0
Other Indebtedness [Member]
Debt Instrument [Line Items]
Senior notes	$ 78.3	$ 73.1
Minimum [Member] | 2.00% to 9.59% Lease Financing Obligations Due Through 2029 [Member]
Debt Instrument [Line Items]
Interest rate	2.00%
Maximum [Member] | 2.00% to 9.59% Lease Financing Obligations Due Through 2029 [Member]
Debt Instrument [Line Items]
Interest rate	9.59%