Employee Benefit Plans (Details) - USD ($) $ in Millions	12 Months Ended
	May 31, 2017	May 31, 2016	May 31, 2015
Employee Benefit Plans (Details) [Line Items]
Unrecognized prior service credit	$ 0.0
Percentage of federal subsidy to sponsors of retiree health care benefit plans	28.00%
Cumulative reduction of its accumulated post-retirement benefit obligation	$ 2.5	$ 3.1	$ 3.0
Defined benefit plans tax expense recognized in AOCI	0.4	(1.8)	(2.5)
Estimated employer contributions in 2015	1.1
Employer contributions to defined contribution plan	7.1	6.8	$ 7.9
Annuities [Member] | Level 3 [Member]
Employee Benefit Plans (Details) [Line Items]
Fair value of annuities	5.8	$ 5.5
Pension Plans [Member]
Employee Benefit Plans (Details) [Line Items]
Estimated net loss to be recognized over next twelve months	$ 2.3
Other Postretirement Benefits [Member]
Employee Benefit Plans (Details) [Line Items]
Expected long-term return on plan assets	0.00%	0.00%	0.00%
Estimated net loss to be recognized over next twelve months	$ 0.1
U.K. [Member] | Pension Plans [Member]
Employee Benefit Plans (Details) [Line Items]
Expected long-term return on plan assets	3.90%	4.20%	5.10%