Condensed Consolidated Statement of Other Comprehensive Income (USD $) In Millions, unless otherwise specified	3 Months Ended
	Apr. 30, 2013	Apr. 30, 2012
Statement of Other Comprehensive Income [Abstract]
Document Period End Date	Apr. 30, 2013
Net income	$ 55.6	$ 78.9
Other comprehensive income, net of tax and reclassification [Abstract]
Net loss on derivative instruments	9.9	(3.4)
Change in net unrealized gain on available-for-sale securities	0.2	0.9
Net change in cumulative foreign currency translation gain	(6.4)	0.3
Total other comprehensive (loss) income	3.7	(2.2)
Total comprehensive income	$ 59.3	$ 76.7