Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Short-term Return on Assets

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Other Comprehensive Income Defined Benefit Plans Tax Expense Benefit

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Other Comprehensive Income (Loss), Defined Benefit Plan, Settlement and Curtailment Gain (Loss), before Tax

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Percentage of federal subsidy to sponsors of retiree health care benefit plans.

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Amount, after tax, of accumulated other comprehensive (income) loss for cost (credit) of benefit change attributable to participants' prior service from plan amendment or plan initiation of defined benefit plan, that has not been recognized in net periodic benefit cost (credit).

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Amount of asset, recognized in statement of financial position, for overfunded defined benefit pension and other postretirement plans.

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Weighted average rate of return on plan assets, reflecting average rate of earnings expected on existing plan assets and expected contributions, used to determine net periodic benefit cost of defined benefit plan.

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Amount of payment to participant of defined benefit plan which decreases benefit obligation. For pension plan, payment includes, but is not limited to, pension benefits and death benefits. For other postretirement plan, payment includes, but is not limited to, prescription drug benefits, health care benefits, life insurance benefits, and legal, educational and advisory services.

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Amount included in accumulated other comprehensive income (loss) for gain (loss) of defined benefit plan expected to be recognized in net periodic benefit (cost) credit for fiscal year following most recent annual statement of financial position.

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Amount of contributions expected to be received by defined benefit plan from employer in next fiscal year following latest fiscal year.

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Amount of decrease in accumulated postretirement benefit obligation for government subsidy related to prescription drug benefits attributed to past service.

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Amount of gain (loss) recognized in net periodic benefit (cost) credit from irrevocable action relieving primary responsibility for benefit obligation and eliminating risk related to obligation and assets used to effect settlement.

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Amount of payment, which decreases plan assets of defined benefit plan, for irrevocable action relieving primary responsibility for benefit obligation and eliminating risk for obligation and assets used to effect settlement. Transaction constituting settlement includes, but is not limited to, making lump-sum cash payment to participant in exchange for their rights to receive specified benefits and purchasing nonparticipating annuity contract.

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Amount of cost for defined contribution plan.

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Employee Benefit Plans (Details) - USD ($) $ in Millions		9 Months Ended	12 Months Ended
Employee Benefit Plans (Details) - USD ($) $ in Millions	Feb. 14, 2018	Feb. 28, 2018	May 31, 2018	May 31, 2017	May 31, 2016
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			$ 2.3	$ 2.5	$ 3.1
Defined benefit plans tax expense recognized in AOCI			20.9	(0.4)	(1.8)
Estimated employer contributions in 2015			1.2
Employer contributions to defined contribution plan			7.2	7.1	6.8
Annuities [Member] \| Level 3 [Member]
Employee Benefit Plans (Details) [Line Items]
Fair value of annuities			5.7	5.8
Pension Plans [Member]
Employee Benefit Plans (Details) [Line Items]
Cost of contracts			0.0	0.0
Estimated net loss to be recognized over next twelve months			0.9
Other Postretirement Benefits [Member]
Employee Benefit Plans (Details) [Line Items]
Lump sum benefit payments			0.8	2.4
Cost of contracts			0.0	0.0
Settlement charge			$ 0.0	$ 0.0	$ 0.0
Expected long-term return on plan assets			0.00%	0.00%	0.00%
Expected short-term return on plan assets			0.00%	0.00%	0.00%
Estimated net loss to be recognized over next twelve months			$ 0.1
U.S. [Member] \| Pension Plans [Member]
Employee Benefit Plans (Details) [Line Items]
Lump sum benefit payments		$ 37.8	6.2	$ 9.6
Cost of contracts	$ 86.3		125.2	0.0
Settlement charge		(57.3)	$ (57.3)	$ 0.0	$ 0.0
Expected long-term return on plan assets			0.00%	0.00%	4.80%
Expected short-term return on plan assets			4.80%	4.80%	0.00%
U.K. [Member] \| Pension Plans [Member]
Employee Benefit Plans (Details) [Line Items]
Lump sum benefit payments			$ 2.1	$ 1.3
Settlement charge			$ 0.0	$ 0.0	$ 0.0
Expected long-term return on plan assets			3.40%	3.90%	4.20%
Expected short-term return on plan assets			0.00%	0.00%	0.00%
Amount reclassified from Accumulated other comprehensive income (loss) [Member] \| Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member]
Employee Benefit Plans (Details) [Line Items]
Accumulated other comprehensive loss reversed		$ (55.0)
Current Assets [Member] \| Other Postretirement Benefits [Member]
Employee Benefit Plans (Details) [Line Items]
Plan assets			$ 0.0	$ 0.0
Current Assets [Member] \| U.S. [Member] \| Pension Plans [Member]
Employee Benefit Plans (Details) [Line Items]
Plan assets			1.6	4.7
Current Assets [Member] \| U.K. [Member] \| Pension Plans [Member]
Employee Benefit Plans (Details) [Line Items]
Plan assets			$ 0.0	$ 0.0