Derivative Instruments (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Jan. 31, 2019	Jan. 31, 2018	Jan. 31, 2017
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Net foreign currency loss (gain)	$ 27.1	$ 32.7	$ 4.3
Notional amount of derivative financial instruments outstanding	$ 1,500.0	$ 1,000.0	$ 600.0
Average maturities of derivatives, days	25 days	31 days	29 days