Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jul. 31, 2015	Jul. 31, 2014	Jul. 31, 2015	Jul. 31, 2014
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balances, January 31, 2015			$ (53.3)
Other comprehensive income (loss) before reclassifications			(3.8)
Pre-tax (gains) losses reclassified from accumulated other comprehensive income			(17.2)
Tax effects			4.0
Total other comprehensive (loss) income	$ (14.3)	$ (3.3)	(17.0)	$ 2.9
Balances, July 31, 2015	(70.3)		(70.3)
Net Unrealized Gains (Losses) on Derivative Instruments
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balances, January 31, 2015			42.8
Other comprehensive income (loss) before reclassifications			7.4
Pre-tax (gains) losses reclassified from accumulated other comprehensive income			(16.8)
Tax effects			(0.7)
Total other comprehensive (loss) income			(10.1)
Balances, July 31, 2015	32.7		32.7
Net Unrealized Gains (Losses) on Available-for-Sale Securities
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balances, January 31, 2015			1.6
Other comprehensive income (loss) before reclassifications			(0.4)
Pre-tax (gains) losses reclassified from accumulated other comprehensive income			(1.0)
Tax effects			0.2
Total other comprehensive (loss) income			(1.2)
Balances, July 31, 2015	0.4		0.4
Defined Benefit Pension Components
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balances, January 31, 2015			(23.7)
Other comprehensive income (loss) before reclassifications			0.4
Pre-tax (gains) losses reclassified from accumulated other comprehensive income			0.6
Tax effects			0.0
Total other comprehensive (loss) income			1.0
Balances, July 31, 2015	(22.7)		(22.7)
Foreign Currency Translation Adjustments
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balances, January 31, 2015			(74.0)
Other comprehensive income (loss) before reclassifications			(11.2)
Pre-tax (gains) losses reclassified from accumulated other comprehensive income			0.0
Tax effects			4.5
Total other comprehensive (loss) income			(6.7)
Balances, July 31, 2015	$ (80.7)		$ (80.7)