Condensed Consolidated Statement of Other Comprehensive Income (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Oct. 31, 2013	Oct. 31, 2012	Oct. 31, 2013	Oct. 31, 2012
Statement of Comprehensive Income [Abstract]
Net income	$ 57.6	$ 29.4	$ 174.9	$ 172.9
Other comprehensive income, net of tax and reclassification [Abstract]
Net loss on derivative instruments	(6.5)	(12.1)	(1.6)	(8.6)
Change in net unrealized gain on available-for-sale securities	0.6	(1.2)	(0.3)	(0.8)
Net change in cumulative foreign currency translation gain	9.3	6.3	3.5	(2.9)
Total other comprehensive (loss) income	3.4	(7.0)	1.6	(12.3)
Total comprehensive income	$ 61.0	$ 22.4	$ 176.5	$ 160.6