Retirement Benefit Plans - Balance Sheet (Details) - USD ($) $ in Millions	Jan. 31, 2019	Jan. 31, 2018
Retirement Benefits [Abstract]
Other long-term liabilities	$ 10.8	$ 37.0
Accumulated other comprehensive loss, before tax	16.3	31.7
Net amount recognized	$ 27.1	$ 68.7

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

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