Condensed Consolidated Statement of Other Comprehensive Income (USD $) In Millions, unless otherwise specified	3 Months Ended
	Apr. 30, 2012	Apr. 30, 2011
Statement of Income and Comprehensive Income [Abstract]
Net income	$ 78.9	$ 69.3
Other comprehensive income, net of tax and reclassification
Net loss on derivative instruments	(3.4)	(7.8)
Change in net unrealized gain on available-for-sale securities	0.9	0.7
Net change in cumulative foreign currency translation gain	0.3	12.5
Total other comprehensive (loss) income	(2.2)	5.4
Total comprehensive income	$ 76.7	$ 74.7