Condensed Consolidated Statement of Other Comprehensive Income (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jul. 31, 2013	Jul. 31, 2012	Jul. 31, 2013	Jul. 31, 2012
Statement of Comprehensive Income [Abstract]
Net income	$ 61.7	$ 64.6	$ 117.3	$ 143.5
Other comprehensive income, net of tax and reclassification [Abstract]
Net loss on derivative instruments	(5.0)	6.9	4.9	3.5
Change in net unrealized gain on available-for-sale securities	(1.3)	(0.5)	(1.1)	0.4
Net change in cumulative foreign currency translation gain	0.8	(9.5)	(5.6)	(9.2)
Total other comprehensive (loss) income	(5.5)	(3.1)	(1.8)	(5.3)
Total comprehensive income	$ 56.2	$ 61.5	$ 115.5	$ 138.2