Employee Benefit Plans (Details) - USD ($) $ in Millions	12 Months Ended
	May 31, 2018	May 31, 2017	May 31, 2016
Cash balance pension plan
Employee benefit plans
Interest crediting rate as a percentage of average 30-year treasury rate	100.00%
Average period of treasury rate used in determination of interest crediting rate	30 years
Average interest crediting rate (as a percent)	4.46%
Defined Benefit Pension Plans
Change in projected benefit obligation:
Projected benefit obligation at beginning of year	$ 145.4	$ 145.7
Service cost	2.4	2.5
Interest cost	4.3	4.2
Participant contributions	0.4	0.3
Net actuarial gain	(2.3)	(2.0)
Benefits and administrative payments	(6.5)	(6.0)
Plan change	0.7
Foreign currency translation adjustment	2.1	0.7
Projected benefit obligation at end of year	146.5	145.4	$ 145.7
Change in the fair value of plan assets:
Fair value of plan assets at beginning of year	118.8	111.0
Actual return on plan assets	11.6	9.9
Employer contributions	8.4	2.9
Participant contributions	0.4	0.3
Benefits and administrative payments	(6.5)	(6.0)
Foreign currency translation adjustment	1.8	0.7
Fair value of plan assets at end of year	134.5	118.8	111.0
Funded status at end of year	(12.0)	(26.6)
Amounts recognized in the consolidated balance sheets
Non-current assets	0.5
Accrued liabilities	(1.2)	(2.7)
Other liabilities and deferred income	(11.3)	(23.9)
Funded status at end of year	(12.0)	(26.6)
Amounts recognized in accumulated other comprehensive loss
Actuarial loss	50.5	58.8
Prior service credit	(0.1)	(0.4)
Total	50.4	58.4
Accumulated benefit obligation	140.2	140.0
Accumulated benefit obligation in excess of plan assets
Fair value of plan assets	0.5
Net Periodic Benefit Cost
Service cost	2.4	2.5	2.5
Interest cost	4.3	4.2	4.5
Expected return on plan assets	(7.3)	(6.5)	(6.5)
Curtailment	0.3
Amortization of prior service cost			0.1
Recognized net actuarial loss	2.3	2.4	2.4
Total	2.0	$ 2.6	$ 3.0
Estimated amounts that will be amortized from accumulated other comprehensive loss into expense over the next fiscal year
Net actuarial loss	1.8
Total	$ 1.8
Domestic plans
Key weighted-average assumptions used in the measurement of the company's projected benefit obligations
Discount rate (as a percent)	4.05%	3.82%
Rate of compensation increase (as a percent)		2.50%
Weighted-average assumptions used to determine net periodic pension expense
Discount rate: (as a percent)	3.82%	3.83%	4.15%
Rate of compensation increase: (as a percent)	2.50%	2.50%	2.50%
Expected long-term rate on plan assets: (as a percent)	7.25%	7.25%	7.25%
Plan Assets
Actual asset allocation (as a percent)	100.00%	100.00%
Domestic plans | Equity securities
Plan Assets
Actual asset allocation (as a percent)	59.00%	62.00%
Domestic plans | Fixed income securities
Plan Assets
Actual asset allocation (as a percent)	22.00%	16.00%
Domestic plans | Other
Plan Assets
Actual asset allocation (as a percent)	19.00%	22.00%
Domestic plans | Minimum | Equity securities
Plan Assets
Target Asset Allocation (as a percent)	45.00%
Domestic plans | Minimum | Fixed income securities
Plan Assets
Target Asset Allocation (as a percent)	15.00%
Domestic plans | Minimum | Other
Plan Assets
Target Asset Allocation (as a percent)	0.00%
Domestic plans | Maximum | Equity securities
Plan Assets
Target Asset Allocation (as a percent)	75.00%
Domestic plans | Maximum | Fixed income securities
Plan Assets
Target Asset Allocation (as a percent)	45.00%
Domestic plans | Maximum | Other
Plan Assets
Target Asset Allocation (as a percent)	25.00%
International plans
Key weighted-average assumptions used in the measurement of the company's projected benefit obligations
Discount rate (as a percent)	1.90%	2.00%
Rate of compensation increase (as a percent)	3.00%	3.00%
Weighted-average assumptions used to determine net periodic pension expense
Discount rate: (as a percent)	2.00%	1.90%	1.90%
Rate of compensation increase: (as a percent)	3.00%	3.00%	3.00%
Expected long-term rate on plan assets: (as a percent)	4.00%	4.00%	4.00%