Equity impact of the cost of common and preferred stock that were repurchased during the period. Recorded using the cost method.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
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-URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21463-112644

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 30
-Section 45
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-URI http://asc.fasb.org/extlink&oid=6405813&loc=d3e23239-112655

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.3-04)
-URI http://asc.fasb.org/extlink&oid=120397183&loc=d3e187085-122770

Name:	us-gaap_TreasuryStockValueAcquiredCostMethod
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Treasury Stock - Schedule of repurchase of common stock (Details) - USD ($) $ in Millions	3 Months Ended				9 Months Ended	35 Months Ended
	Feb. 28, 2021	Feb. 29, 2020	Nov. 30, 2019	Aug. 31, 2019	Feb. 28, 2021	Feb. 28, 2021	May 31, 2020	Mar. 31, 2020	Mar. 31, 2018
Stockholders' Equity Attributable to Parent [Abstract]
Authorized amount of stock to be repurchased							$ 100.0	$ 50.0	$ 50.0
Total current Board authorizations		$ (13.0)	$ (7.1)	$ (12.6)		$ (32.7)
Less repurchases made under these authorizations	$ 67.3				$ 67.3	$ 67.3
Number of common stock repurchased (in shares)	0				0