CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (Parenthetical) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jul. 31, 2015	Jul. 31, 2014	Jul. 31, 2015	Jul. 31, 2014
Statement of Comprehensive Income [Abstract]
Net gain (loss) on derivative instruments - tax effect	$ 0.8	$ (0.4)	$ (0.7)	$ (1.1)
Change in net unrealized loss on available-for-sale securities, tax effect	0.3	0.4	0.2	0.0
Net change in cumulative foreign currency translation (loss) gain, tax effect	$ 0.7	$ 0.9	$ 4.5	$ (0.4)