Consolidated Statement of Changes in Stockholders Equity (Parenthetical) - USD ($) $ in Millions	12 Months Ended
May 31, 2020	May 31, 2019	May 31, 2018
Statement of Stockholders' Equity [Abstract]
Pension and postretirement adjustments, tax portion	$ 0.4	$ 0.5	$ 20.9
Net effect		$ 16.0

Amount, after reclassification adjustment, of tax (expense) benefit for (increase) decrease in accumulated other comprehensive income of defined benefit plan.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
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-Subparagraph (i-k)
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Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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