Income Taxes Components Of Deferred Tax Assets and Liabilities (Details) (USD $) In Millions, unless otherwise specified	Jan. 31, 2013	Jan. 31, 2012
Income Tax Disclosure [Abstract]
Nonqualified stock options	$ 67.5	$ 71.6
Research and development tax credit carryforwards	54.0	49.3
Foreign tax credit carryforwards	0	0.1
Accrued compensation and benefits	34.5	35.6
Other accruals not currently deductible for tax	15.3	14.2
Purchased technology and capitalized software	9.8	20.6
Fixed assets	18.5	15.9
Tax loss carryforwards	21.0	12.4
Deferred Revenue	28.5	16.9
Other	2.2	3.7
Total deferred tax assets	251.3	240.3
Less: valuation allowance	(51.3)	(47.5)
Net deferred tax assets	200.0	192.8
Tax method change on advanced payments	(3.1)	(6.3)
Unremitted earnings of foreign subsidiaries	(31.9)	(20.6)
Total deferred tax liability	(35.0)	(26.9)
Net deferred tax assets	$ 165.0	$ 165.9