Financial Instruments Cost and Fair Value of Financial Instuments (Details) (USD $) In Millions, unless otherwise specified	Apr. 30, 2014		Jan. 31, 2014		Apr. 30, 2013	Jan. 31, 2013
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents	$ 1,609.6		$ 1,853.0		$ 1,655.8	$ 1,612.2
Derivative contracts, Amortized Cost	7.9	[1]	10.8	[1]
Derivative contracts, Gross unrealized gains	5.6	[1]	14.8	[1]
Derivative contracts, Gross unrealized losses	(6.5)	[1]	(6.0)	[1]
Derivative contracts, Fair Value	7.0	[1]	19.6	[1]
Amortized Cost	1,575.4		1,545.3
Gross unrealized gains	16.1		22.4
Gross unrealized losses	(12.5)		(10.5)
Fair Value	1,579.0		1,557.2
Short-term available for sale
Schedule of Available-for-sale Securities [Line Items]
Mutual funds, Amortized Cost	37.3		35.6
Mutual funds, Gross unrealized gains	4.7		3.3
Mutual funds, Gross unrealized losses	0		0
Mutual funds, Fair Value	42.0		38.9
Short-term available for sale | Commercial paper and corporate debt securities
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Amortized Cost	383.3		261.0
Marketable securities, Gross unrealized gains	0		0
Marketable securities, Gross unrealized losses	0		0
Marketable securities, Fair Value	383.3		261.0
Short-term available for sale | Certificate of deposit and time deposits
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Amortized Cost	33.6		37.1
Marketable securities, Gross unrealized gains	0		0
Marketable securities, Gross unrealized losses	0		0
Marketable securities, Fair Value	33.6		37.1
Short-term available for sale | Agency bond
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Amortized Cost	18.7		42.7
Marketable securities, Gross unrealized gains	0		0
Marketable securities, Gross unrealized losses	0		0
Marketable securities, Fair Value	18.7		42.7
Short-term available for sale | U.S. government agency securities
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Amortized Cost	7.5		11.3
Marketable securities, Gross unrealized gains	0		0
Marketable securities, Gross unrealized losses	0		0
Marketable securities, Fair Value	7.5		11.3
Short-term available for sale | Municipal securities
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Amortized Cost	13.5		11.7
Marketable securities, Gross unrealized gains	0		0
Marketable securities, Gross unrealized losses	0		0
Marketable securities, Fair Value	13.5		11.7
Short-term available for sale | Other
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Amortized Cost	11.5	[2]	11.4	[2]
Marketable securities, Gross unrealized gains	0	[2]	0	[2]
Marketable securities, Gross unrealized losses	0	[2]	0	[2]
Marketable securities, Fair Value	11.5	[2]	11.4	[2]
Long-term available for sale | Agency bond
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Amortized Cost	41.3		43.3
Marketable securities, Gross unrealized gains	0.1		0.1
Marketable securities, Gross unrealized losses	0		0
Marketable securities, Fair Value	41.4		43.4
Long-term available for sale | U.S. government agency securities
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Amortized Cost	9.1		9.8
Marketable securities, Gross unrealized gains	0.1		0
Marketable securities, Gross unrealized losses	0		0
Marketable securities, Fair Value	9.2		9.8
Long-term available for sale | Municipal securities
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Amortized Cost	33.4		43.5
Marketable securities, Gross unrealized gains	0.2		0.3
Marketable securities, Gross unrealized losses			0
Marketable securities, Fair Value	33.6		43.8
Long-term available for sale | Corporate debt securities
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Amortized Cost	183.4		179.7
Marketable securities, Gross unrealized gains	0.6		0.7
Marketable securities, Gross unrealized losses	0		(0.1)
Marketable securities, Fair Value	184.0		180.3
Convertible debt securities
Schedule of Available-for-sale Securities [Line Items]
Convertible debt securities, Amortized Cost	21.4	[3]	21.4	[3]
Convertible debt securities, Gross unrealized gains	4.8	[3]	3.2	[3]
Convertible debt securities, Gross unrealized losses	(6.0)	[3]	(4.4)	[3]
Convertible debt securities, Fair Value	20.2	[3]	20.2	[3]
Certificates of deposit and time deposits
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents	314.1	[4]	280.7	[4]
Cash equivalents, Fair Value	314.1	[4]	280.7	[4]
Commercial paper
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents	203.4	[4]	280.5	[4]
Cash equivalents, Fair Value	203.4	[4]	280.5	[4]
Municipal securities
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents			2.0	[4]
Cash equivalents, Fair Value			2.0	[4]
Money market funds
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents	256.0	[4]	262.8	[4]
Cash equivalents, Fair Value	256.0	[4]	262.8	[4]
Level 1
Schedule of Available-for-sale Securities [Line Items]
Derivative contracts, Fair Value	0	[1]	0	[1]
Fair Value	518.1		521.1
Level 1 | Short-term available for sale
Schedule of Available-for-sale Securities [Line Items]
Mutual funds, Fair Value	42.0		38.9
Level 1 | Short-term available for sale | Commercial paper and corporate debt securities
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Fair Value	133.0		95.4
Level 1 | Short-term available for sale | Certificate of deposit and time deposits
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Fair Value	0		0
Level 1 | Short-term available for sale | Agency bond
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Fair Value	18.7		42.7
Level 1 | Short-term available for sale | U.S. government agency securities
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Fair Value	7.5		11.3
Level 1 | Short-term available for sale | Municipal securities
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Fair Value	13.5		11.7
Level 1 | Short-term available for sale | Other
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Fair Value	11.5	[2]	11.4	[2]
Level 1 | Long-term available for sale | Agency bond
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Fair Value	41.4		43.4
Level 1 | Long-term available for sale | U.S. government agency securities
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Fair Value	9.2		9.8
Level 1 | Long-term available for sale | Municipal securities
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Fair Value	33.6		43.8
Level 1 | Long-term available for sale | Corporate debt securities
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Fair Value	184.0		180.3
Level 1 | Convertible debt securities
Schedule of Available-for-sale Securities [Line Items]
Convertible debt securities, Fair Value	0	[3]	0	[3]
Level 1 | Certificates of deposit and time deposits
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents, Fair Value	23.7	[4]	30.4	[4]
Level 1 | Commercial paper
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents, Fair Value	0	[4]	0	[4]
Level 1 | Municipal securities
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents, Fair Value			2.0	[4]
Level 1 | Money market funds
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents, Fair Value	0	[4]	0	[4]
Level 2
Schedule of Available-for-sale Securities [Line Items]
Derivative contracts, Fair Value	2.2	[1]	10.5	[1]
Fair Value	1,035.9		1,006.8
Level 2 | Short-term available for sale
Schedule of Available-for-sale Securities [Line Items]
Mutual funds, Fair Value	0		0
Level 2 | Short-term available for sale | Commercial paper and corporate debt securities
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Fair Value	250.3		165.6
Level 2 | Short-term available for sale | Certificate of deposit and time deposits
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Fair Value	33.6		37.1
Level 2 | Short-term available for sale | Agency bond
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Fair Value	0		0
Level 2 | Short-term available for sale | U.S. government agency securities
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Fair Value	0		0
Level 2 | Short-term available for sale | Municipal securities
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Fair Value	0		0
Level 2 | Short-term available for sale | Other
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Fair Value	0	[2]	0	[2]
Level 2 | Long-term available for sale | Agency bond
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Fair Value	0		0
Level 2 | Long-term available for sale | U.S. government agency securities
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Fair Value	0		0
Level 2 | Long-term available for sale | Municipal securities
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Fair Value	0		0
Level 2 | Long-term available for sale | Corporate debt securities
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Fair Value	0		0
Level 2 | Convertible debt securities
Schedule of Available-for-sale Securities [Line Items]
Convertible debt securities, Fair Value	0	[3]	0	[3]
Level 2 | Certificates of deposit and time deposits
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents, Fair Value	290.4	[4]	250.3	[4]
Level 2 | Commercial paper
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents, Fair Value	203.4	[4]	280.5	[4]
Level 2 | Municipal securities
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents, Fair Value			0	[4]
Level 2 | Money market funds
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents, Fair Value	256.0	[4]	262.8	[4]
Level 3
Schedule of Available-for-sale Securities [Line Items]
Derivative contracts, Fair Value	4.8	[1]	9.1	[1]
Fair Value	25.0		29.3
Level 3 | Short-term available for sale
Schedule of Available-for-sale Securities [Line Items]
Mutual funds, Fair Value	0		0
Level 3 | Short-term available for sale | Commercial paper and corporate debt securities
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Fair Value	0		0
Level 3 | Short-term available for sale | Certificate of deposit and time deposits
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Fair Value	0		0
Level 3 | Short-term available for sale | Agency bond
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Fair Value	0		0
Level 3 | Short-term available for sale | U.S. government agency securities
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Fair Value	0		0
Level 3 | Short-term available for sale | Municipal securities
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Fair Value	0		0
Level 3 | Short-term available for sale | Other
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Fair Value	0	[2]	0	[2]
Level 3 | Long-term available for sale | Agency bond
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Fair Value	0		0
Level 3 | Long-term available for sale | U.S. government agency securities
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Fair Value	0		0
Level 3 | Long-term available for sale | Municipal securities
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Fair Value	0		0
Level 3 | Long-term available for sale | Corporate debt securities
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Fair Value	0		0
Level 3 | Convertible debt securities
Schedule of Available-for-sale Securities [Line Items]
Convertible debt securities, Fair Value	20.2	[3]	20.2	[3]
Level 3 | Certificates of deposit and time deposits
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents, Fair Value	0	[4]	0	[4]
Level 3 | Commercial paper
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents, Fair Value	0	[4]	0	[4]
Level 3 | Municipal securities
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents, Fair Value			0	[4]
Level 3 | Money market funds
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents, Fair Value	$ 0	[4]	$ 0	[4]

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

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

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

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