Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Oct. 31, 2018	Oct. 31, 2017	Oct. 31, 2018	Oct. 31, 2017
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	$ (241.6)	$ 315.5	$ (256.0)	$ 733.6
Other comprehensive income (loss) before reclassifications			(37.7)
Pre-tax losses reclassified from accumulated other comprehensive loss			9.3
Tax effects			(5.3)
Total other comprehensive (loss) income	(6.6)	(2.6)	(33.7)	23.0
Ending balance	(338.3)	107.3	(338.3)	107.3
Net Unrealized Gains (Losses) on Derivative Instruments
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance			(16.6)
Other comprehensive income (loss) before reclassifications			23.0
Pre-tax losses reclassified from accumulated other comprehensive loss			9.0
Tax effects			(2.9)
Total other comprehensive (loss) income			29.1
Ending balance	12.5		12.5
Net Unrealized Gains (Losses) on Available-for-Sale Debt Securities
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance			1.3
Other comprehensive income (loss) before reclassifications			1.8
Pre-tax losses reclassified from accumulated other comprehensive loss			0.0
Tax effects			(0.1)
Total other comprehensive (loss) income			1.7
Ending balance	3.0		3.0
Defined Benefit Pension Components
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance			(29.3)
Other comprehensive income (loss) before reclassifications			14.1
Pre-tax losses reclassified from accumulated other comprehensive loss			0.3
Tax effects			(2.8)
Total other comprehensive (loss) income			11.6
Ending balance	(17.7)		(17.7)
Foreign Currency Translation Adjustments
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance			(79.2)
Other comprehensive income (loss) before reclassifications			(76.6)
Pre-tax losses reclassified from accumulated other comprehensive loss			0.0
Tax effects			0.5
Total other comprehensive (loss) income			(76.1)
Ending balance	(155.3)		(155.3)
Accumulated other comprehensive loss
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(150.9)	(152.9)	(123.8)	(178.5)
Ending balance	$ (157.5)	$ (155.5)	$ (157.5)	$ (155.5)