CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) shares in Millions, $ in Millions	Total	Common stock and additional paid-in capital	Accumulated other comprehensive (loss) income	Retained earnings
Balance (in shares) at Jan. 31, 2013		223.6
Beginning Balance at Jan. 31, 2013	$ 2,043.2	$ 1,449.8	$ (5.7)	$ 599.1
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common shares issued under stock plans (in shares)		13.6
Common shares issued under stock plans	288.2	$ 288.2
Stock-based compensation expense	132.2	132.2
Tax benefits from employee stock plans	(12.2)	$ (12.2)
Net (loss) income	228.8			228.8
Other comprehensive (loss) income	5.1		5.1
Repurchase and retirement of common shares (in shares)		(10.5)
Repurchase and retirement of common shares	(423.8)	$ (220.7)		(203.1)
Balance (in shares) at Jan. 31, 2014		226.7
Ending Balance at Jan. 31, 2014	2,261.5	$ 1,637.3	(0.6)	624.8
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common shares issued under stock plans (in shares)		7.2
Common shares issued under stock plans	135.4	$ 135.4
Stock-based compensation expense	165.6	$ 165.6
Net (loss) income	81.8			81.8
Other comprehensive (loss) income	(52.7)		(52.7)
Repurchase and retirement of common shares (in shares)		(6.9)
Repurchase and retirement of common shares	$ (372.4)	$ (165.2)		(207.2)
Balance (in shares) at Jan. 31, 2015	227.0	227.0
Ending Balance at Jan. 31, 2015	$ 2,219.2	$ 1,773.1	(53.3)	499.4
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common shares issued under stock plans (in shares)		5.9
Common shares issued under stock plans	59.2	$ 59.2
Stock-based compensation expense	197.2	197.2
Tax benefits from employee stock plans	0.3	$ 0.3
Net (loss) income	(330.5)			(330.5)
Other comprehensive (loss) income	(67.8)		(67.8)
Repurchase and retirement of common shares (in shares)		(8.5)
Repurchase and retirement of common shares	$ (458.0)	$ (208.3)		(249.7)
Balance (in shares) at Jan. 31, 2016	224.4	224.4
Ending Balance at Jan. 31, 2016	$ 1,619.6	$ 1,821.5	$ (121.1)	$ (80.8)