Revenue Recognition (Narrative) (Details) $ in Millions	3 Months Ended		9 Months Ended
	Oct. 31, 2020 USD ($)	Oct. 31, 2019 USD ($)	Oct. 31, 2020 USD ($) category	Oct. 31, 2019 USD ($)
Revenue from Contract with Customer [Abstract]
Number of revenue categories | category			3
Remaining performance obligation	$ 3,580.0		$ 3,580.0
Contract with customer, liability, revenue recognized	481.9	$ 398.5	1,910.0	$ 1,580.0
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-11-01
Revenue from Contract with Customer [Abstract]
Remaining performance obligation	$ 2,380.0		$ 2,380.0
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligation percentage	67.00%		67.00%
Performance obligation, expected timing of satisfaction (in years)	12 months		12 months
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-02-01
Revenue from Contract with Customer [Abstract]
Remaining performance obligation	$ 1,200.0		$ 1,200.0
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligation percentage	33.00%		33.00%
Performance obligation, expected timing of satisfaction (in years)	3 years		3 years