Income Taxes - Income Taxes Components Of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Millions	Jan. 31, 2016	Jan. 31, 2015
Income Tax Disclosure [Abstract]
Stock-based compensation	$ 37.5	$ 39.9
Research and development tax credit carryforwards	91.3	62.6
Foreign tax credit carryforwards	51.1	0.0
Accrued compensation and benefits	41.5	43.6
Other accruals not currently deductible for tax	23.6	18.4
Purchased technology and capitalized software	64.3	53.9
Fixed assets	18.6	16.2
Tax loss carryforwards	17.6	16.0
Deferred Revenue	56.7	48.0
Other	13.9	7.4
Total deferred tax assets	416.1	306.0
Less: valuation allowance	(398.0)	(70.8)
Net deferred tax assets	18.1	235.2
Indefinite lived intangibles	(54.1)	(40.7)
Unremitted earnings of foreign subsidiaries	(22.4)	(9.4)
Total deferred tax liabilities	(76.5)	(50.1)
Net deferred tax liabilities	$ (58.4)
Net deferred tax assets		$ 185.1