Stockholders' Equity (Schedule of Components of Accumulated Other Comprehensive Income) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Feb. 28, 2016	Feb. 22, 2015	Feb. 28, 2016	Feb. 22, 2015
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	$ (65.0)	$ (79.8)	$ (86.6)	$ (128.1)
Gain (loss)	1.8	(0.6)	2.6	12.9
Reclassification realized in net earnings	(0.1)	2.6	20.7	37.4
Ending Balance	(63.3)	(77.8)	(63.3)	(77.8)
Foreign Currency Translation Adjustment
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	(0.8)	0.8	(1.7)	(4.7)
Gain (loss)	0.0	(2.0)	0.9	(3.8)
Reclassification realized in net earnings	0.0	0.0	0.0	7.3
Ending Balance	(0.8)	(1.2)	(0.8)	(1.2)
Unrealized Gains (Losses) on Marketable Securities
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	0.1	0.1	0.1	0.1
Gain (loss)	0.0	0.0	0.0	0.0
Reclassification realized in net earnings	0.0	0.0	0.0	0.0
Ending Balance	0.1	0.1	0.1	0.1
Unrealized Gains (Losses) on Derivatives
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	1.8	(23.0)	(19.1)	(50.4)
Gain (loss)	1.8	1.4	1.7	2.1
Reclassification realized in net earnings	0.0	1.6	21.0	28.3
Ending Balance	3.6	(20.0)	3.6	(20.0)
Benefit Plan Funding Position
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	(66.1)	(57.7)	(65.9)	(73.1)
Gain (loss)	0.0	0.0	0.0	14.6
Reclassification realized in net earnings	(0.1)	1.0	(0.3)	1.8
Ending Balance	$ (66.2)	$ (56.7)	$ (66.2)	$ (56.7)