RESTRUCTURING (Liabilities for Initiatives and Changes) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	May 26, 2013
Ralcorp Restructuring
Restructuring Cost and Reserve [Line Items]
Beginning balance	$ 0
Costs incurred and charged to expense	28.4
Costs paid or otherwise settled	0
Changes in estimates	0
Ending balance	28.4
Acquisition-Related Restructuring
Restructuring Cost and Reserve [Line Items]
Beginning balance	4.3
Costs incurred and charged to expense	7.0
Costs paid or otherwise settled	(8.4)
Changes in estimates	(1.4)
Ending balance	1.5
Administrative Efficiency Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Beginning balance	2.4
Costs incurred and charged to expense	1.5
Costs paid or otherwise settled	(3.3)
Changes in estimates	(0.2)
Ending balance	0.4
Network Optimization Plan
Restructuring Cost and Reserve [Line Items]
Beginning balance	7.8
Costs incurred and charged to expense	3.7
Costs paid or otherwise settled	(8.0)
Changes in estimates	(3.3)
Ending balance	0.2
Multi-employer Pension Cost | Ralcorp Restructuring
Restructuring Cost and Reserve [Line Items]
Beginning balance	0
Costs incurred and charged to expense	11.2
Costs paid or otherwise settled	0
Changes in estimates	0
Ending balance	11.2
Severance and Related Costs | Ralcorp Restructuring
Restructuring Cost and Reserve [Line Items]
Beginning balance	0
Costs incurred and charged to expense	17.2
Costs paid or otherwise settled	0
Changes in estimates	0
Ending balance	17.2
Severance and Related Costs | Acquisition-Related Restructuring
Restructuring Cost and Reserve [Line Items]
Beginning balance	4.3
Costs incurred and charged to expense	6.1
Costs paid or otherwise settled	(7.8)
Changes in estimates	(1.4)
Ending balance	1.2
Severance and Related Costs | Administrative Efficiency Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Beginning balance	2.1
Costs incurred and charged to expense	1.3
Costs paid or otherwise settled	(2.8)
Changes in estimates	(0.2)
Ending balance	0.4
Severance and Related Costs | Network Optimization Plan
Restructuring Cost and Reserve [Line Items]
Beginning balance	7.0
Costs incurred and charged to expense	1.0
Costs paid or otherwise settled	(4.5)
Changes in estimates	(3.3)
Ending balance	0.2
Plan implementation costs | Acquisition-Related Restructuring
Restructuring Cost and Reserve [Line Items]
Beginning balance	0
Costs incurred and charged to expense	0.9
Costs paid or otherwise settled	(0.6)
Changes in estimates	0
Ending balance	0.3
Plan implementation costs | Administrative Efficiency Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Beginning balance	0.3
Costs incurred and charged to expense	0.2
Costs paid or otherwise settled	(0.5)
Changes in estimates	0
Ending balance	0
Plan implementation costs | Network Optimization Plan
Restructuring Cost and Reserve [Line Items]
Beginning balance	0.8
Costs incurred and charged to expense	2.7
Costs paid or otherwise settled	(3.5)
Changes in estimates	0
Ending balance	$ 0