Leases - Lease cost (Details) - USD ($) $ in Millions	3 Months Ended
Apr. 30, 2021	Apr. 30, 2020
Lease, Cost [Abstract]
Deferred lease payments	$ 2.3
Selling, general and administrative expenses
Lease, Cost [Abstract]
Lease costs	$ 13.6	$ 22.4

Amount of obligations incurred classified as other, payable within one year or the normal operating cycle, if longer.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section 45
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=121566466&loc=d3e6935-107765

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.19(a))
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant