Selected Quarterly Financial Information (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended									12 Months Ended
	Jan. 31, 2017	Oct. 31, 2016	Jul. 31, 2016		Apr. 30, 2016	Jan. 31, 2016	Oct. 31, 2015	Jul. 31, 2015	Apr. 30, 2015	Jan. 31, 2017	Jan. 31, 2016	Jan. 31, 2015
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net revenue	$ 478.8	$ 489.6	$ 550.7	[1]	$ 511.9	$ 648.3	$ 599.8	$ 609.5	$ 646.5	$ 2,031.0	$ 2,504.1	$ 2,512.2
Gross profit	395.9	408.1	465.6	[1]	419.5	553.4	508.8	516.5	554.7	1,689.1	2,133.4	2,170.1
Loss from operations	(167.1)	(119.9)	(62.9)	[1]	(149.7)	(9.7)	(14.8)	4.3	21.5	(499.6)	1.3	120.7
Provision for income taxes	(5.2)	(13.5)	(25.2)	[1]	(14.4)	(16.7)	(21.3)	(269.5)	(2.7)	(58.3)	(310.2)	(1.2)
Net (loss) income	$ (173.4)	$ (142.8)	$ (98.2)	[1]	$ (167.7)	$ (37.2)	$ (43.8)	$ (268.6)	$ 19.1	$ (582.1)	$ (330.5)	$ 81.8
Basic net income (loss) per share (usd per share)	$ (0.78)	$ (0.64)	$ (0.44)	[1]	$ (0.75)	$ (0.17)	$ (0.19)	$ (1.18)	$ 0.08	$ (2.61)	$ (1.46)	$ 0.36
Diluted net income (loss) per share (usd per share)	$ (0.78)	$ (0.64)	$ (0.44)	[1]	$ (0.75)	$ (0.17)	$ (0.19)	$ (1.18)	$ 0.08	$ (2.61)	$ (1.46)	$ 0.35
Income from operations includes following items [Abstract]
Stock-based compensation expense	$ 59.3	$ 56.6	$ 54.3	[1]	$ 51.6	$ 56.1	$ 50.2	$ 40.7	$ 50.2	$ 221.8	$ 197.2	$ 165.6
Amortization of acquisition related intangibles	17.3	17.2	18.5	[1]	18.8	$ 19.9	$ 19.7	20.2	$ 22.4	71.8	82.2
Restructuring charges and other facility exit costs, net	$ 9.0	$ 3.2	$ 16.0		52.3					80.5	0.0	3.1
Stock-based compensation expense										$ (221.8)	$ (197.2)	$ (165.6)
Restatement Adjustment
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Provision for income taxes								$ (33.1)
Income from operations includes following items [Abstract]
Stock-based compensation expense					$ 5.3

[1] Certain first quarter fiscal 2017 balances have been revised to reflect the adoption of ASU 2016-09. As the adoption occurred in the second quarter of fiscal 2017, we are required to reflect any adjustments as of February 1, 2016, the beginning of the annual period that includes the interim period of adoption, and are required to revise our reported quarterly results for the first quarter. The revision resulted in a $5.3 million decrease of stock-based compensation expense from the previously reported expense. See Note 1, "Business and Summary of Significant Accounting Policies" for further discussion on the adoption.