Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Oct. 31, 2019	Oct. 31, 2018	Oct. 31, 2019	Oct. 31, 2018
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	$ (194.3)	$ (241.6)	$ (210.9)	$ (256.0)
Other comprehensive income (loss) before reclassifications			(9.8)
Pre-tax losses reclassified from accumulated other comprehensive loss			(10.4)
Tax effects			(1.1)
Total other comprehensive income (loss)	14.4	(6.6)	(21.3)	(33.7)
Ending balance	(171.5)	(338.3)	(171.5)	(338.3)
Accumulated other comprehensive loss
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(170.7)	(150.9)	(135.0)	(123.8)
Ending balance	(156.3)	$ (157.5)	(156.3)	$ (157.5)
Net Unrealized Gains (Losses) on Derivative Instruments
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance			15.0
Other comprehensive income (loss) before reclassifications			4.3
Pre-tax losses reclassified from accumulated other comprehensive loss			(7.0)
Tax effects			(1.6)
Total other comprehensive income (loss)			(4.3)
Ending balance	10.7		10.7
Net Unrealized Gains (Losses) on Available-for-Sale Debt Securities
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance			3.3
Other comprehensive income (loss) before reclassifications			1.8
Pre-tax losses reclassified from accumulated other comprehensive loss			0.0
Tax effects			(0.4)
Total other comprehensive income (loss)			1.4
Ending balance	4.7		4.7
Defined Benefit Pension Components
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance			(16.3)
Other comprehensive income (loss) before reclassifications			0.1
Pre-tax losses reclassified from accumulated other comprehensive loss			(3.4)
Tax effects			0.8
Total other comprehensive income (loss)			(2.5)
Ending balance	(18.8)		(18.8)
Foreign Currency Translation Adjustments
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance			(137.0)
Other comprehensive income (loss) before reclassifications			(16.0)
Pre-tax losses reclassified from accumulated other comprehensive loss			0.0
Tax effects			0.1
Total other comprehensive income (loss)			(15.9)
Ending balance	$ (152.9)		$ (152.9)