Selected Quarterly Financial Information (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Jan. 31, 2014	Oct. 31, 2013	Jul. 31, 2013	Apr. 30, 2013	Jan. 31, 2013	Oct. 31, 2012	Jul. 31, 2012	Apr. 30, 2012	Jan. 31, 2014	Jan. 31, 2013	Jan. 31, 2012
Quarterly Financial Information Disclosure [Abstract]
Net revenue	$ 586.6	$ 555.2	$ 561.7	$ 570.4	$ 606.9	$ 548.0	$ 568.7	$ 588.6	$ 2,273.9	$ 2,312.2	$ 2,215.6
Gross profit	514.7	488.1	493.9	502.9	544.9	490.1	508.9	529.8	1,999.6	2,073.7	1,986.5
Income from operations	51.7	68.1	83.6	81.4	84.6	34.4	92.9	94.0	284.8	305.9	355.6
Provision for income taxes	(2.4)	(11.6)	(20.1)	(17.0)	(11.6)	(4.9)	(27.5)	(18.6)	(51.1)	(62.6)	(77.6)
Net income	53.9	57.6	61.7	55.6	74.5	29.4	64.6	78.9	228.8	247.4	285.3
Basic net income per share	$ 0.24	$ 0.26	$ 0.28	$ 0.25	$ 0.33	$ 0.13	$ 0.28	$ 0.35	$ 1.02	$ 1.09	$ 1.25
Diluted net income per share	$ 0.23	$ 0.25	$ 0.27	$ 0.24	$ 0.32	$ 0.13	$ 0.28	$ 0.34	$ 1.00	$ 1.07	$ 1.22
Income from operations includes following items [Abstract]
Stock-based compensation expense	36.1	31.6	31.0	33.5	37.5	51.9	33.5	33.4	132.2	156.3	108.8
Amortization of acquisition related intangibles	20.6	18.2	20.3	21.6	23.0	23.7	17.5	17.6	80.7	81.8
Additions	$ 6.3	$ 4.4	$ 1.7	$ 0.4	$ 7.2	$ 36.7	$ 0	$ 0	$ 12.8	$ 43.9	$ (1.3)