Employee Benefit Plans - Asset Allocations in the Pension Plan (Details)	May 31, 2019	May 31, 2018
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	26.40%	26.50%
Small cap equity
Defined Benefit Plan Disclosure [Line Items]
Target Asset Allocations	5.00%
Actual Asset Allocations	5.30%	5.60%
International equity
Defined Benefit Plan Disclosure [Line Items]
Target Asset Allocations	8.00%
Actual Asset Allocations	7.80%	7.90%
Fixed income
Defined Benefit Plan Disclosure [Line Items]
Target Asset Allocations	45.00%
Actual Asset Allocations	45.00%	44.20%
Absolute return strategy funds
Defined Benefit Plan Disclosure [Line Items]
Target Asset Allocations	16.00%
Actual Asset Allocations	13.30%	15.80%
Cash
Defined Benefit Plan Disclosure [Line Items]
Target Asset Allocations	0.00%
Actual Asset Allocations	2.20%	0.00%