Employee Benefit Plans - Asset Allocations in the Pension Plan (Details)	May 31, 2020	May 31, 2019
Defined Benefit Plan Disclosure [Line Items]
Target Asset Allocations	100.00%
Actual Asset Allocations	100.00%	100.00%
Large cap equity
Defined Benefit Plan Disclosure [Line Items]
Target Asset Allocations	26.00%
Actual Asset Allocations	25.00%	26.40%
Small cap equity
Defined Benefit Plan Disclosure [Line Items]
Target Asset Allocations	5.00%
Actual Asset Allocations	4.40%	5.30%
International equity
Defined Benefit Plan Disclosure [Line Items]
Target Asset Allocations	8.00%
Actual Asset Allocations	6.70%	7.80%
Fixed income
Defined Benefit Plan Disclosure [Line Items]
Target Asset Allocations	45.00%
Actual Asset Allocations	51.50%	45.00%
Absolute return strategy funds
Defined Benefit Plan Disclosure [Line Items]
Target Asset Allocations	16.00%
Actual Asset Allocations	11.90%	13.30%
Cash
Defined Benefit Plan Disclosure [Line Items]
Target Asset Allocations	0.00%
Actual Asset Allocations	0.50%	2.20%