Derivative Instruments (Details) - USD ($) $ in Millions	3 Months Ended
	Apr. 30, 2019	Apr. 30, 2018
Derivative [Line Items]
Weighted Average Notional Amount Of Foreign Currency Derivatives	$ 1,300.0	$ 1,400.0
Derivative, Average Remaining Maturity	24 days	30 days
Cash Flow Hedging [Member]
Derivative [Line Items]
Derivative, Notional Amount	$ 4.5