Financial Instruments - Cost and Fair Value of Financial Instruments (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Jan. 31, 2014		Jan. 31, 2013		Jan. 31, 2012	Jan. 31, 2011
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents	$ 1,853.0		$ 1,612.2		$ 1,156.9	$ 1,075.1
Derivative Instruments And Hedges at Amortized Cost	10.8	[1]	10.2	[1]
Unrealized Gain on Foreign Currency Derivatives, before Tax	14.8	[1]	9.2	[1]
Unrealized Loss on Foreign Currency Derivatives, before Tax	(6.0)	[1]	(5.9)	[1]
Derivative Contracts, Fair Value	19.6	[1]	13.5	[1]
Amortized Cost Securities	1,545.3		2,029.2
Unrealized Gain on Securities	22.4		16.9
Unrealized Loss on Securities	(10.5)		(8.1)
Total	1,557.2		2,038.0
Marketable Securities, Current
Schedule of Available-for-sale Securities [Line Items]
Trading Securities	35.6		31.1
Trading Securities, Unrealized Holding Gain	3.3		4.2
Trading Securities, Unrealized Holding Loss	0		0
Other Assets
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost			18.1	[2]
Available-for-sale Securities, Gross Unrealized Gains			1.6	[2]
Available-for-sale Securities, Gross Unrealized Losses			(2.2)	[2]
Available-for-sale Securities, Fair Value			17.5	[2]
Convertible Debt Securities, Amortized Cost	21.4	[3]
Convertible Debt Securities, Unrealized Gains	3.2	[3]
Convertible Debt Securities, Unrealized Losses	(4.4)	[3]
Convertible Debt Securities, Fair Value	20.2	[3]
Fair Value, Inputs, Level 1
Schedule of Available-for-sale Securities [Line Items]
Derivative Contracts, Fair Value	0	[1]	0	[1]
Total	521.1		678.3
Fair Value, Inputs, Level 1 | Marketable Securities, Current
Schedule of Available-for-sale Securities [Line Items]
Trading Securities	38.9		35.3
Fair Value, Inputs, Level 1 | Other Assets
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair Value			0	[2]
Convertible Debt Securities, Fair Value	0	[3]
Fair Value, Inputs, Level 2
Schedule of Available-for-sale Securities [Line Items]
Derivative Contracts, Fair Value	10.5	[1]	2.8	[1]
Total	1,006.8		1,327.3
Fair Value, Inputs, Level 2 | Marketable Securities, Current
Schedule of Available-for-sale Securities [Line Items]
Trading Securities	0		0
Fair Value, Inputs, Level 2 | Other Assets
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair Value			0	[2]
Convertible Debt Securities, Fair Value	0	[3]
Fair Value, Inputs, Level 3
Schedule of Available-for-sale Securities [Line Items]
Derivative Contracts, Fair Value			10.7	[1]
Total	29.3		32.4
Fair Value, Inputs, Level 3 | Marketable Securities, Current
Schedule of Available-for-sale Securities [Line Items]
Trading Securities	0		0
Fair Value, Inputs, Level 3 | Other Assets
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair Value			17.5	[2]
Convertible Debt Securities, Fair Value	20.2	[3]
Commercial paper and corporate debt securities | Marketable Securities, Current
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost	261.0		122.9
Available-for-sale Securities, Gross Unrealized Gains	0		0.1
Available-for-sale Securities, Gross Unrealized Losses	0		0
Available-for-sale Securities, Fair Value	261.0		123.0
Commercial paper and corporate debt securities | Fair Value, Inputs, Level 1 | Marketable Securities, Current
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair Value	95.4		40.4
Commercial paper and corporate debt securities | Fair Value, Inputs, Level 2 | Marketable Securities, Current
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair Value	165.6		82.6
Commercial paper and corporate debt securities | Fair Value, Inputs, Level 3 | Marketable Securities, Current
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair Value	0		0
Certificates of deposit and time deposits | Marketable Securities, Current
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost	37.1		15.1
Available-for-sale Securities, Gross Unrealized Gains	0		0
Available-for-sale Securities, Gross Unrealized Losses	0		0
Available-for-sale Securities, Fair Value	37.1		15.1
Certificates of deposit and time deposits | Fair Value, Inputs, Level 1 | Marketable Securities, Current
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair Value	0		10.0
Certificates of deposit and time deposits | Fair Value, Inputs, Level 2 | Marketable Securities, Current
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair Value	37.1		5.1
Certificates of deposit and time deposits | Fair Value, Inputs, Level 3 | Marketable Securities, Current
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair Value	0		0
U.S. treasury securities | Marketable Securities, Current
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost			83.3
Available-for-sale Securities, Gross Unrealized Gains			0
Available-for-sale Securities, Gross Unrealized Losses			0
Available-for-sale Securities, Fair Value			83.3
U.S. treasury securities | Marketable Securities, Noncurrent
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost	43.3		145.2
Available-for-sale Securities, Gross Unrealized Gains	0.1		0.1
Available-for-sale Securities, Gross Unrealized Losses	0		0
Available-for-sale Securities, Fair Value	43.4		145.3
U.S. treasury securities | Fair Value, Inputs, Level 1 | Marketable Securities, Current
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair Value			83.3
U.S. treasury securities | Fair Value, Inputs, Level 1 | Marketable Securities, Noncurrent
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair Value	43.4		145.3
U.S. treasury securities | Fair Value, Inputs, Level 2 | Marketable Securities, Current
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair Value			0
U.S. treasury securities | Fair Value, Inputs, Level 2 | Marketable Securities, Noncurrent
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair Value	0		0
U.S. treasury securities | Fair Value, Inputs, Level 3 | Marketable Securities, Current
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair Value			0
U.S. treasury securities | Fair Value, Inputs, Level 3 | Marketable Securities, Noncurrent
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair Value	0		0
US government agency securities | Marketable Securities, Current
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost	11.3		79.5
Available-for-sale Securities, Gross Unrealized Gains	0		0
Available-for-sale Securities, Gross Unrealized Losses	0		0
Available-for-sale Securities, Fair Value	11.3		79.5
US government agency securities | Marketable Securities, Noncurrent
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost	9.8		50.8
Available-for-sale Securities, Gross Unrealized Gains	0		0.2
Available-for-sale Securities, Gross Unrealized Losses	0		0
Available-for-sale Securities, Fair Value	9.8		51.0
US government agency securities | Fair Value, Inputs, Level 1 | Marketable Securities, Current
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair Value	11.3		79.5
US government agency securities | Fair Value, Inputs, Level 1 | Marketable Securities, Noncurrent
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair Value	9.8		51.0
US government agency securities | Fair Value, Inputs, Level 2 | Marketable Securities, Current
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair Value	0		0
US government agency securities | Fair Value, Inputs, Level 2 | Marketable Securities, Noncurrent
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair Value	0		0
US government agency securities | Fair Value, Inputs, Level 3 | Marketable Securities, Current
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair Value	0		0
US government agency securities | Fair Value, Inputs, Level 3 | Marketable Securities, Noncurrent
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair Value	0		0
Sovereign Debt | Marketable Securities, Current
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost	42.7		1.0
Available-for-sale Securities, Gross Unrealized Gains	0		0
Available-for-sale Securities, Gross Unrealized Losses	0		0
Available-for-sale Securities, Fair Value	42.7		1.0
Sovereign Debt | Marketable Securities, Noncurrent
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost			1.0
Available-for-sale Securities, Gross Unrealized Gains			0
Available-for-sale Securities, Gross Unrealized Losses			0
Available-for-sale Securities, Fair Value			1.0
Sovereign Debt | Fair Value, Inputs, Level 1 | Marketable Securities, Current
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair Value	42.7		0
Sovereign Debt | Fair Value, Inputs, Level 1 | Marketable Securities, Noncurrent
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair Value			0
Sovereign Debt | Fair Value, Inputs, Level 2 | Marketable Securities, Current
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair Value	0		1.0
Sovereign Debt | Fair Value, Inputs, Level 2 | Marketable Securities, Noncurrent
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair Value			1.0
Sovereign Debt | Fair Value, Inputs, Level 3 | Marketable Securities, Current
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair Value	0		0
Sovereign Debt | Fair Value, Inputs, Level 3 | Marketable Securities, Noncurrent
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair Value			0
Municipal securities | Marketable Securities, Current
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost	11.7		4.6
Available-for-sale Securities, Gross Unrealized Gains	0		0
Available-for-sale Securities, Gross Unrealized Losses	0		0
Available-for-sale Securities, Fair Value	11.7		4.6
Municipal securities | Marketable Securities, Noncurrent
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost	43.5		36.0
Available-for-sale Securities, Gross Unrealized Gains	0.3		0.1
Available-for-sale Securities, Gross Unrealized Losses	0		0
Available-for-sale Securities, Fair Value	43.8		36.1
Municipal securities | Fair Value, Inputs, Level 1 | Marketable Securities, Current
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair Value	11.7		4.6
Municipal securities | Fair Value, Inputs, Level 1 | Marketable Securities, Noncurrent
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair Value	43.8		36.1
Municipal securities | Fair Value, Inputs, Level 2 | Marketable Securities, Current
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair Value	0		0
Municipal securities | Fair Value, Inputs, Level 2 | Marketable Securities, Noncurrent
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair Value	0		0
Municipal securities | Fair Value, Inputs, Level 3 | Marketable Securities, Current
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair Value	0		0
Municipal securities | Fair Value, Inputs, Level 3 | Marketable Securities, Noncurrent
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair Value	0		0
Other | Marketable Securities, Current
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost	11.4	[4]	0.3
Available-for-sale Securities, Gross Unrealized Gains	0	[4]	0
Available-for-sale Securities, Gross Unrealized Losses	0	[4]	0
Available-for-sale Securities, Fair Value	11.4	[4]	0.3
Other | Fair Value, Inputs, Level 1 | Marketable Securities, Current
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair Value	11.4	[4]	0.3
Other | Fair Value, Inputs, Level 2 | Marketable Securities, Current
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair Value	0	[4]	0
Other | Fair Value, Inputs, Level 3 | Marketable Securities, Current
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair Value	0	[4]	0
Corporate debt securities | Marketable Securities, Noncurrent
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost	179.7		172.1
Available-for-sale Securities, Gross Unrealized Gains	0.7		1.4
Available-for-sale Securities, Gross Unrealized Losses	(0.1)		0
Available-for-sale Securities, Fair Value	180.3		173.5
Corporate debt securities | Fair Value, Inputs, Level 1 | Marketable Securities, Noncurrent
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair Value	180.3		173.5
Corporate debt securities | Fair Value, Inputs, Level 2 | Marketable Securities, Noncurrent
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair Value	0		0
Corporate debt securities | Fair Value, Inputs, Level 3 | Marketable Securities, Noncurrent
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair Value	0		0
Taxable Auction-Rate Securities | Marketable Securities, Noncurrent
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost			4.2
Available-for-sale Securities, Gross Unrealized Gains			0
Available-for-sale Securities, Gross Unrealized Losses			0
Available-for-sale Securities, Fair Value			4.2
Taxable Auction-Rate Securities | Fair Value, Inputs, Level 1 | Marketable Securities, Noncurrent
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair Value			0
Taxable Auction-Rate Securities | Fair Value, Inputs, Level 2 | Marketable Securities, Noncurrent
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair Value			0
Taxable Auction-Rate Securities | Fair Value, Inputs, Level 3 | Marketable Securities, Noncurrent
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair Value			4.2
Certificates of deposit and time deposits
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents	280.7	[5]	392.4	[5]
Cash and Cash Equivalents, Fair Value Disclosure	280.7	[5]	392.4	[5]
Certificates of deposit and time deposits | Fair Value, Inputs, Level 1
Schedule of Available-for-sale Securities [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure	30.4	[5]	17.2	[5]
Certificates of deposit and time deposits | Fair Value, Inputs, Level 2
Schedule of Available-for-sale Securities [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure	250.3	[5]	375.2	[5]
Certificates of deposit and time deposits | Fair Value, Inputs, Level 3
Schedule of Available-for-sale Securities [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure	0	[5]	0	[5]
Municipal securities
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents	2.0	[5]	1.8	[5]
Cash and Cash Equivalents, Fair Value Disclosure	2.0	[5]	1.8	[5]
Municipal securities | Fair Value, Inputs, Level 1
Schedule of Available-for-sale Securities [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure	2.0	[5]	1.8	[5]
Municipal securities | Fair Value, Inputs, Level 2
Schedule of Available-for-sale Securities [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure	0	[5]	0	[5]
Municipal securities | Fair Value, Inputs, Level 3
Schedule of Available-for-sale Securities [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure	0	[5]	0	[5]
Commercial Paper
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents	280.5	[5]	263.3	[5]
Cash and Cash Equivalents, Fair Value Disclosure	280.5	[5]	263.3	[5]
Commercial Paper | Fair Value, Inputs, Level 1
Schedule of Available-for-sale Securities [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure	0	[5]	0	[5]
Commercial Paper | Fair Value, Inputs, Level 2
Schedule of Available-for-sale Securities [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure	280.5	[5]	263.3	[5]
Commercial Paper | Fair Value, Inputs, Level 3
Schedule of Available-for-sale Securities [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure	0	[5]	0	[5]
Money Market Funds
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents	262.8	[5]	596.3	[5]
Cash and Cash Equivalents, Fair Value Disclosure	262.8	[5]	596.3	[5]
Money Market Funds | Fair Value, Inputs, Level 1
Schedule of Available-for-sale Securities [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure	0	[5]	0	[5]
Money Market Funds | Fair Value, Inputs, Level 2
Schedule of Available-for-sale Securities [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure	262.8	[5]	596.3	[5]
Money Market Funds | Fair Value, Inputs, Level 3
Schedule of Available-for-sale Securities [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure	0	[5]	0	[5]
Rabbi Trust | Marketable Securities, Current
Schedule of Available-for-sale Securities [Line Items]
Trading Securities	38.9		35.3
Not Designated as Hedging Instrument | Other Assets
Schedule of Available-for-sale Securities [Line Items]
Derivative Contracts, Fair Value	$ 9.1	[1]

[1] Included in “Prepaid expenses and other current assets,” "Other assets," or “Other accrued liabilities” in the accompanying Consolidated Balance Sheets.

[2] Considered "available for sale" securities and included in "Other assets" in the accompanying Consolidated Balance Sheets.

[3] Considered "available for sale" and included in "Other assets" in the accompanying Consolidated Balance Sheets.

[4] Consists of agency discount notes, U.S. treasury bills, and other short-term securities.

[5] Included in “Cash and cash equivalents” in the accompanying Consolidated Balance Sheets.