Income Taxes Components Of Deferred Tax Assets and Liabilities (Details) (USD $) In Millions, unless otherwise specified	Jan. 31, 2014	Jan. 31, 2013
Income Tax Disclosure [Abstract]
Nonqualified stock options	$ 37.4	$ 67.5
Research and development tax credit carryforwards	78.4	54.0
Foreign tax credit carryforwards	16.3	0
Accrued compensation and benefits	38.6	34.5
Other accruals not currently deductible for tax	14.5	15.3
Purchased technology and capitalized software	23.4	9.8
Fixed assets	17.5	18.5
Tax loss carryforwards	12.6	21.0
Deferred Revenue	33.1	28.5
Other	5.1	2.2
Total deferred tax assets	276.9	251.3
Less: valuation allowance	(67.2)	(51.3)
Net deferred tax assets	209.7	200.0
Tax method change on advanced payments	0	(3.1)
Unremitted earnings of foreign subsidiaries	(21.8)	(31.9)
Total deferred tax liability	(21.8)	(35.0)
Net deferred tax assets	$ 187.9	$ 165.0