Retirement Benefits and Postemployment Benefits (Schedule of assumptions used to determine net periodic expense) (Details)	12 Months Ended
	May 31, 2020	May 26, 2019	May 27, 2018
Defined Benefit Pension Plans [Member]
Defined Benefit Plan Weighted Average Assumptions Used In Calculating Net Periodic Benefit Cost [Abstract]
Discount rate	3.91%	4.20%	4.08%
Service cost effective rate	4.19%	4.34%	4.37%
Interest cost effective rate	3.47%	3.92%	3.45%
Rate of salary increases	4.17%	4.27%	4.25%
Expected long-term rate of return on plan assets	6.95%	7.25%	7.88%
Other Postretirement Benefit Plans [Member]
Defined Benefit Plan Weighted Average Assumptions Used In Calculating Net Periodic Benefit Cost [Abstract]
Discount rate	3.79%	4.17%	3.92%
Service cost effective rate	4.04%	4.27%	4.27%
Interest cost effective rate	3.28%	3.80%	3.24%
Rate of salary increases	0.00%	0.00%	0.00%
Expected long-term rate of return on plan assets	5.67%	5.67%	7.59%
Postemployment Benefit Plans [Member]
Defined Benefit Plan Weighted Average Assumptions Used In Calculating Net Periodic Benefit Cost [Abstract]
Discount rate	3.10%	3.60%	2.87%
Service cost effective rate	3.51%	3.99%	3.54%
Interest cost effective rate	2.84%	3.37%	2.67%
Rate of salary increases	4.47%	4.44%	4.46%
Expected long-term rate of return on plan assets	0.00%	0.00%	0.00%