CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) (USD $) In Millions, unless otherwise specified	9 Months Ended
	Oct. 31, 2013	Oct. 31, 2012
Operating activities [Abstract]:
Net income	$ 174.9	$ 172.9
Adjustments to reconcile net income to net cash provided by operating activities [Abstract]:
Depreciation and amortization	95.7	93.1
Stock-based compensation expense	96.1	118.8
Excess tax benefits from stock-based compensation	0.8	(27.4)
Restructuring benefits	6.5	36.7
Other Operating Activities, Cash Flow Statement	(3.1)	4.4
Changes in operating assets and liabilities, net of business combinations	9.1	5.0
Net cash provided by operating activities	380.0	403.5
Investing activities [Abstract]:
Purchases of marketable securities	(969.8)	(1,103.1)
Sales of marketable securities	329.9	207.0
Maturities of marketable securities	395.1	436.6
Capital expenditures	(55.0)	(44.7)
Acquisitions, net of cash acquired	(68.0)	(204.2)
Other investing activities	(15.7)	(22.1)
Net cash used in investing activities	(383.5)	(730.5)
Financing activities [Abstract]:
Proceeds from issuance of common stock, net of issuance costs	183.4	199.6
Repurchases of common stock	(318.7)	(340.5)
Proceeds from Lines of Credit	0	110.0
Excess tax benefits from stock-based compensation	(0.8)	27.4
Net cash used in financing activities	(136.1)	(3.5)
Effect of exchange rate changes on cash and cash equivalents	0.8	0.6
Net increase in cash and cash equivalents	(138.8)	(329.9)
Cash and cash equivalents at beginning of fiscal year	1,612.2	1,156.9
Cash and cash equivalents at end of period	$ 1,473.4	$ 827.0