Derivative Instruments (Details) $ in Millions	3 Months Ended		9 Months Ended
	Oct. 31, 2019 USD ($)	Oct. 31, 2018 USD ($)	Oct. 31, 2019 USD ($)	Oct. 31, 2018 USD ($)
Derivative [Line Items]
Weighted Average Notional Amount Of Foreign Currency Derivatives	$ 1,100.0	$ 1,500.0	$ 1,200.0	$ 1,400.0
Derivative, Average Remaining Maturity	28 days	24 days	26 days	27 days
Net Investment Hedging [Member]
Derivative [Line Items]
Derivative, Number of Instruments Held		0		0
Cash Flow Hedging [Member]
Derivative [Line Items]
Derivative, Number of Instruments Held		0		0
Derivative, Notional Amount	$ 4.5		$ 4.5