Selected Quarterly Financial Information (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Jan. 31, 2012	Oct. 31, 2011	Jul. 31, 2011	Apr. 30, 2011	Jan. 31, 2011	Oct. 31, 2010	Jul. 31, 2010	Apr. 30, 2010	Jan. 31, 2012	Jan. 31, 2011	Jan. 31, 2010
Selected Quarterly Financial Information (Unaudited) [Abstract]
Revenue, Net	$ 592.4	$ 548.6	$ 546.3	$ 528.3	$ 527.7	$ 476.7	$ 472.8	$ 474.6	$ 2,215.6	$ 1,951.8	$ 1,713.7
Gross Profit	534.9	489.0	488.9	473.7	479.3	428.2	424.4	423.3	1,986.5	1,755.2	1,521.9
Income from operations	91.8	90.2	95.0	78.6	71.6	69.2	79.8	50.8	355.6	271.4	65.6
Provision for income taxes	(20.9)	(18.5)	(23.0)	(15.2)	(11.4)	(18.1)	(20.0)	(10.5)	(77.6)	(60.0)	(26.7)
Net income	72.0	72.8	71.2	69.3	61.6	53.6	59.9	36.9	285.3	212.0	58.0
Earnings Per Share, Basic	$ 0.32	$ 0.32	$ 0.31	$ 0.30	$ 0.27	$ 0.24	$ 0.26	$ 0.16	$ 1.25	$ 0.93	$ 0.25
Earnings Per Share, Diluted	$ 0.31	$ 0.32	$ 0.30	$ 0.29	$ 0.26	$ 0.23	$ 0.25	$ 0.16	$ 1.22	$ 0.90	$ 0.25
income from operations includes following items [Abstract]
Stock Based Compensation Expense	30.0	25.6	27.3	25.9	18.4	17.0	21.0	24.3	108.8	80.7	93.6
Amortization of acquisition realted Intangible Assets	18.6	19.3	17.8	14.6	14.3	14.1	13.6	13.9	70.3	55.9
Restructuring Charges	$ 0	$ 0	$ (1.3)	$ 0	$ 1.8	$ 0	$ 1.9	$ 7.1	$ (1.3)	$ 10.8	$ 48.2