Retirement Benefits and Postemployment Benefits (Schedule of components of net periodic benefit expense) (Details) - USD ($) $ in Millions	12 Months Ended
	May 31, 2020	May 26, 2019	May 27, 2018
Defined Benefit Pension Plans [Member]
Components of Net Periodic Benefit Cost [Abstract]
Service cost	$ 92.7	$ 94.6	$ 102.9
Interest cost	230.5	248.0	217.9
Expected return on plan assets	(449.9)	(445.8)	(480.2)
Amortization of losses	106.0	109.8	177.0
Amortization of prior service costs (credits)	1.6	1.5	1.9
Other adjustments	0.0	0.0	0.0
Settlement or curtailment losses	0.0	0.3	0.0
Net (income) expense	(19.1)	8.4	19.5
Other Postretirement Benefit Plans [Member]
Components of Net Periodic Benefit Cost [Abstract]
Service cost	9.4	9.9	11.6
Interest cost	27.1	33.1	30.1
Expected return on plan assets	(42.1)	(40.4)	(52.2)
Amortization of losses	(2.1)	0.6	0.8
Amortization of prior service costs (credits)	(5.5)	(5.5)	(5.4)
Other adjustments	0.0	0.0	0.0
Settlement or curtailment losses	0.0	0.0	0.0
Net (income) expense	(13.2)	(2.3)	(15.1)
Postemployment Benefit Plans [Member]
Components of Net Periodic Benefit Cost [Abstract]
Service cost	8.3	7.6	8.6
Interest cost	2.6	3.0	2.3
Expected return on plan assets	0.0	0.0	0.0
Amortization of losses	0.4	0.1	0.8
Amortization of prior service costs (credits)	0.9	0.7	0.6
Other adjustments	17.7	6.7	6.7
Settlement or curtailment losses	0.0	0.0	0.0
Net (income) expense	$ 29.9	$ 18.1	$ 19.0