Leases - Operating Lease Cost and Additional Lease Information (Details) - USD ($) $ in Thousands	3 Months Ended
	Aug. 31, 2020	Aug. 31, 2019	May 31, 2020
Leases [Abstract]
Operating lease costs	$ 17,100	$ 17,200
Other information related to operating leases
Cash paid for amounts included in the measurement of operating lease liabilities	12,254	12,342
Operating lease right-of-use assets obtained in exchange for new and renewed operating lease liabilities	$ 9,317	$ 6,828
Weighted-average remaining lease term - operating leases	5 years 1 month 6 days		5 years 2 months 8 days
Weighted-average discount rate - operating leases	2.62%		2.66%