CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) (USD $) In Millions, unless otherwise specified	6 Months Ended
	Jul. 31, 2013	Jul. 31, 2012
Operating activities [Abstract]:
Net income	$ 117.3	$ 143.5
Adjustments to reconcile net income to net cash provided by operating activities [Abstract]:
Depreciation and amortization	65.1	58.1
Stock-based compensation expense	64.6	66.9
Excess tax benefits from stock-based compensation	(3.2)	(28.1)
Restructuring benefits	2.1	0
Other Operating Activities, Cash Flow Statement	2.0	3.9
Changes in operating assets and liabilities, net of business combinations	41.5	2.1
Net cash provided by operating activities	289.4	246.4
Investing activities [Abstract]:
Purchases of marketable securities	(697.3)	(725.3)
Sales of marketable securities	215.1	138.9
Maturities of marketable securities	231.9	250.5
Capital expenditures	(42.6)	(28.2)
Acquisitions, net of cash acquired	(47.2)	(69.2)
Other investing activities	(5.4)	(18.0)
Net cash used in investing activities	(345.5)	(451.3)
Financing activities [Abstract]:
Proceeds from issuance of common stock, net of issuance costs	79.8	158.8
Repurchases of common stock	(239.8)	(210.3)
Excess tax benefits from stock-based compensation	3.2	28.1
Net cash used in financing activities	(156.8)	(23.4)
Effect of exchange rate changes on cash and cash equivalents	1.7	1.6
Net increase in cash and cash equivalents	(211.2)	(226.7)
Cash and cash equivalents at beginning of fiscal year	1,612.2	1,156.9
Cash and cash equivalents at end of period	$ 1,401.0	$ 930.2