Condensed Consolidated Statement of Other Comprehensive Income (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jul. 31, 2012	Jul. 31, 2011	Jul. 31, 2012	Jul. 31, 2011
Statement of Other Comprehensive Income [Abstract]
Net income	$ 64.6	$ 71.2	$ 143.5	$ 140.5
Other comprehensive income, net of tax and reclassification [Abstract]
Net loss on derivative instruments	6.9	8.3	3.5	0.5
Change in net unrealized gain on available-for-sale securities	(0.5)	0.3	0.4	1.0
Net change in cumulative foreign currency translation gain	(9.5)	0.9	(9.2)	13.4
Total other comprehensive (loss) income	(3.1)	9.5	(5.3)	14.9
Total comprehensive income	$ 61.5	$ 80.7	$ 138.2	$ 155.4