Financial Instruments (Derivative Narrative) (Details) - USD ($) $ in Millions	9 Months Ended
	Oct. 31, 2019	Jan. 31, 2019
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Net gain expected to be recognized in next 24 months	$ 10.7
Minimum | Foreign currency contracts
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative instrument, term	1 month
Maximum | Foreign currency contracts
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative instrument, term	12 months
Designated as hedging instrument
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative, notional amount	$ 1,250.0	$ 803.5
Derivatives not designated as hedging instruments | Foreign currency contracts
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative, notional amount	$ 357.1	$ 579.8