Income Taxes Components Of Deferred Tax Assets and Liabilities (Details) (USD $) In Millions, unless otherwise specified	Jan. 31, 2012	Jan. 31, 2011
Income Taxes [Abstract]
Nonqualified stock options	$ 71.6	$ 69.0
Research and development tax credit carryforwards	49.3	64.0
Foreign tax credit carryforwards	0.1	16.6
Accrued compensation and benefits	35.6	33.7
Other accruals not currently deductible for tax	31.1	20.8
Purchased technology and capitalized software	20.6	25.3
Fixed assets	15.9	15.1
Tax loss carryforwards	12.4	6.3
Other	3.7	2.6
Total deferred tax assets	240.3	253.4
Less: valuation allowance	(47.5)	(42.9)
Net deferred tax assets	192.8	210.5
Tax method change on advanced payments	(6.3)	(9.4)
Unremitted earnings of foreign subsidiaries	(20.6)	(53.6)
Total deferred tax liability	(26.9)	(63.0)
Net deferred tax assets	$ 165.9	$ 147.5