PENSION AND POSTRETIREMENT BENEFITS - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	May 28, 2017	May 29, 2016	May 31, 2015	May 25, 2014	Dec. 31, 2016	Nov. 09, 2016
Defined Benefit Plan Disclosure [Line Items]
Expense resulting from special termination benefits granted		$ 25.6
Expense related to expected incurrence of certain multi-employer plan withdrawal costs	$ 4.0	31.8
Fair value of certain investments	669.8
Fair value of funds which have imposed such gates	0.1
Additional expense related to expected incurrence of certain withdrawal costs	4.0	31.8	$ 0.4
Expense related to defined contribution plans	$ 18.0	35.4	40.6
Generally less than
Defined Benefit Plan Disclosure [Line Items]
Maximum allowable funding percentage to be in critical status	65.00%
Maximum allowable funding percentage to be in endangered status status	80.00%
Generally at least
Defined Benefit Plan Disclosure [Line Items]
Minimum required funding percentage to be in the green zone	80.00%
Percentage of plan's total contribution under Forms 5500 (more than)	5.00%			5.00%
Private equity funds
Defined Benefit Plan Disclosure [Line Items]
Unfunded commitments for additional investments	$ 84.5
Natural resources funds
Defined Benefit Plan Disclosure [Line Items]
Unfunded commitments for additional investments	28.3
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Accumulated benefit obligation	$ 3,500.0	$ 3,800.0
Effective discount rate assumption	3.90%	3.83%			4.11%
Decrease to underfunded status of the pension plans	$ 18.1	$ 18.8
Lump-sum settlement payments	287.5	0.0
Settlement charge	13.8	0.0	0.0
Benefit to accumulated other comprehensive income (loss)	62.2
Expense resulting from special termination benefits granted	1.5	25.6	6.9
Charge reflecting year-end write-off of actuarial losses	1.2	348.5
Pre-tax reduction in total pension benefit cost associated with change in accounting estimate	(0.9)	$ 413.7	13.3
Anticipated contributions to plans in fiscal 2018	$ 12.8
Other Benefits
Defined Benefit Plan Disclosure [Line Items]
Effective discount rate assumption	3.33%	3.18%
Decrease to underfunded status of the pension plans	$ 0.0	$ 0.0
Lump-sum settlement payments	0.0	0.0
Settlement charge	0.0	0.0	0.0
Expense resulting from special termination benefits granted	0.0	0.0	0.0
Pre-tax reduction in total pension benefit cost associated with change in accounting estimate	(1.2)	$ 0.2	6.1
Anticipated contributions to plans in fiscal 2018	18.7
Ardent Mills
Defined Benefit Plan Disclosure [Line Items]
Expense resulting from special termination benefits granted			$ 6.9
Spinoff | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Pension curtailment gain within other comprehensive income (loss)	19.5
Effective discount rate assumption		3.86%				4.04%
Decrease to underfunded status of the pension plans	66.0
Discontinued operations
Defined Benefit Plan Disclosure [Line Items]
Expense related to expected incurrence of certain multi-employer plan withdrawal costs	2.1	$ 2.0
Restructuring activities
Defined Benefit Plan Disclosure [Line Items]
Expense related to expected incurrence of certain multi-employer plan withdrawal costs	1.9	$ 29.8
Change in Assumptions for Defined Benefit Plans | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Pre-tax reduction in total pension benefit cost associated with change in accounting estimate	$ 27.0