Commitments and Contingencies (Details) - USD ($) $ in Millions	12 Months Ended
	May 31, 2017	May 31, 2016	May 31, 2015
Operating Leased Assets [Line Items]
Operating lease expense	$ 24.9	$ 25.7	$ 24.2
Capital lease amortization expense	1.1	0.8	$ 0.2
Open standby letters of credit	$ 5.3	$ 5.3
Minimum [Member]
Operating Leased Assets [Line Items]
Capital lease period	1 year
Maximum [Member]
Operating Leased Assets [Line Items]
Capital lease period	10 years