Financial Instruments Cost and Fair Value of Financial Instruments (Details) - USD ($) $ in Millions		Jul. 31, 2016		Jan. 31, 2016		Jul. 31, 2015	Jan. 31, 2015
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents		$ 1,467.3		$ 1,353.0		$ 1,473.1	$ 1,410.6
Derivative contracts, Amortized Cost	[1]	3.2		1.5
Derivative contracts, Gross unrealized gains	[1]	7.1		7.8
Derivative contracts, Gross unrealized losses	[1]	(10.8)		(7.4)
Derivative contracts, Fair Value	[1]	(0.5)		1.9
Amortized Cost		1,977.8		2,310.6
Gross unrealized gains		13.8		11.1
Gross unrealized losses		(12.1)		(11.0)
Fair Value		1,979.5		2,310.7
Marketable Securities, Current
Schedule of Available-for-sale Securities [Line Items]
Mutual funds, Amortized Cost		43.7		38.8
Mutual funds, Gross unrealized gains		1.9		0.4
Mutual funds, Gross unrealized losses		0.0		(1.2)
Mutual funds, Fair Value		45.6		38.0
Marketable Securities, Current | Agency bonds
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Amortized Cost		41.9		40.0
Marketable securities, Gross unrealized gains		0.0		0.0
Marketable securities, Gross unrealized losses		0.0		(0.1)
Marketable securities, Fair Value		41.9		39.9
Marketable Securities, Current | Asset backed securities
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Amortized Cost		10.8		7.3
Marketable securities, Gross unrealized gains		0.0		0.0
Marketable securities, Gross unrealized losses		0.0		0.0
Marketable securities, Fair Value		10.8		7.3
Marketable Securities, Current | Certificates of deposit
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Amortized Cost		55.4		190.3
Marketable securities, Gross unrealized gains		0.0		0.0
Marketable securities, Gross unrealized losses		0.0		0.0
Marketable securities, Fair Value		55.4		190.3
Marketable Securities, Current | Commercial paper
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Amortized Cost		119.4		141.1
Marketable securities, Gross unrealized gains		0.0		0.0
Marketable securities, Gross unrealized losses		0.0		0.0
Marketable securities, Fair Value		119.4		141.1
Marketable Securities, Current | Corporate bonds
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Amortized Cost		267.2
Marketable securities, Gross unrealized gains		0.2
Marketable securities, Gross unrealized losses		(0.1)
Marketable securities, Fair Value		267.3
Marketable Securities, Current | Corporate debt securities
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Amortized Cost				377.1
Marketable securities, Gross unrealized gains				0.1
Marketable securities, Gross unrealized losses				(0.3)
Marketable securities, Fair Value				376.9
Marketable Securities, Current | Municipal bonds
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Amortized Cost				9.7
Marketable securities, Gross unrealized gains				0.0
Marketable securities, Gross unrealized losses				0.0
Marketable securities, Fair Value				9.7
Marketable Securities, Current | Sovereign debt
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Amortized Cost		19.6		20.1
Marketable securities, Gross unrealized gains		0.0		0.0
Marketable securities, Gross unrealized losses		0.0		0.0
Marketable securities, Fair Value		19.6		20.1
Marketable Securities, Current | U.S. government securities
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Amortized Cost		37.6		74.6
Marketable securities, Gross unrealized gains		0.0		0.0
Marketable securities, Gross unrealized losses		0.0		0.0
Marketable securities, Fair Value		37.6		74.6
Marketable Securities, Noncurrent | Agency bonds
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Amortized Cost		52.0		56.8
Marketable securities, Gross unrealized gains		0.3		0.1
Marketable securities, Gross unrealized losses		0.0		0.0
Marketable securities, Fair Value		52.3		56.9
Marketable Securities, Noncurrent | Asset backed securities
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Amortized Cost		58.9		36.5
Marketable securities, Gross unrealized gains		0.2		0.1
Marketable securities, Gross unrealized losses		0.0		0.0
Marketable securities, Fair Value		59.1		36.6
Marketable Securities, Noncurrent | Certificates of deposit
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Amortized Cost		1.8
Marketable securities, Gross unrealized gains		0.0
Marketable securities, Gross unrealized losses		0.0
Marketable securities, Fair Value		1.8
Marketable Securities, Noncurrent | Corporate bonds
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Amortized Cost		276.1
Marketable securities, Gross unrealized gains		1.5
Marketable securities, Gross unrealized losses		(0.1)
Marketable securities, Fair Value		277.5
Marketable Securities, Noncurrent | Corporate debt securities
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Amortized Cost				320.9
Marketable securities, Gross unrealized gains				0.3
Marketable securities, Gross unrealized losses				(0.8)
Marketable securities, Fair Value				320.4
Marketable Securities, Noncurrent | Municipal bonds
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Amortized Cost		9.5		2.9
Marketable securities, Gross unrealized gains		0.1		0.0
Marketable securities, Gross unrealized losses		0.0		0.0
Marketable securities, Fair Value		9.6		2.9
Marketable Securities, Noncurrent | Sovereign debt
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Amortized Cost		10.8		16.9
Marketable securities, Gross unrealized gains		0.0		0.0
Marketable securities, Gross unrealized losses		0.0		0.0
Marketable securities, Fair Value		10.8		16.9
Marketable Securities, Noncurrent | U.S. government securities
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Amortized Cost		94.2		98.4
Marketable securities, Gross unrealized gains		0.3		0.3
Marketable securities, Gross unrealized losses		0.0		(0.1)
Marketable securities, Fair Value		94.5		98.6
Convertible debt securities
Schedule of Available-for-sale Securities [Line Items]
Convertible debt securities, Amortized Cost	[2]	6.3		2.5
Convertible debt securities, Gross unrealized gains	[2]	2.2		2.0
Convertible debt securities, Gross unrealized losses	[2]	(1.1)		(1.1)
Convertible debt securities, Fair Value	[2]	7.4		3.4
Agency bonds
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents		44.2	[3]	8.5	[4]
Cash equivalents, Fair Value		44.2	[3]	8.5	[4]
Certificates of deposit
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents		181.3	[3]	267.6	[4]
Cash equivalents, Fair Value		181.3	[3]	267.6	[4]
Commercial paper
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents		296.9	[3]	106.6	[4]
Cash equivalents, Fair Value		296.9	[3]	106.6	[4]
Corporate bonds
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents	[3]	8.7
Cash equivalents, Fair Value	[3]	8.7
Custody cash deposit
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents		22.5	[3]	2.1	[4]
Cash equivalents, Fair Value		22.5	[3]	2.1	[4]
Money market funds
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents		143.8	[3]	382.4	[4]
Cash equivalents, Fair Value		143.8	[3]	382.4	[4]
Municipal bonds
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents		5.0	[3]	5.0	[4]
Cash equivalents, Fair Value		5.0	[3]	5.0	[4]
U.S. government securities
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents		167.0	[3]	103.0	[4]
Cash equivalents, Fair Value		167.0	[3]	103.0	[4]
Level 1
Schedule of Available-for-sale Securities [Line Items]
Derivative contracts, Fair Value	[1]	0.0		0.0
Fair Value		1,312.2		1,594.4
Level 1 | Marketable Securities, Current
Schedule of Available-for-sale Securities [Line Items]
Mutual funds, Fair Value		45.6		38.0
Level 1 | Marketable Securities, Current | Agency bonds
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Fair Value		41.9		39.9
Level 1 | Marketable Securities, Current | Asset backed securities
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Fair Value		0.0		0.0
Level 1 | Marketable Securities, Current | Certificates of deposit
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Fair Value		55.4		190.3
Level 1 | Marketable Securities, Current | Commercial paper
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Fair Value		0.0		0.0
Level 1 | Marketable Securities, Current | Corporate bonds
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Fair Value		267.3
Level 1 | Marketable Securities, Current | Corporate debt securities
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Fair Value				376.9
Level 1 | Marketable Securities, Current | Municipal bonds
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Fair Value				9.7
Level 1 | Marketable Securities, Current | Sovereign debt
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Fair Value		0.0		0.0
Level 1 | Marketable Securities, Current | U.S. government securities
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Fair Value		37.6		74.6
Level 1 | Marketable Securities, Noncurrent | Agency bonds
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Fair Value		52.3		56.9
Level 1 | Marketable Securities, Noncurrent | Asset backed securities
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Fair Value		0.0		0.0
Level 1 | Marketable Securities, Noncurrent | Certificates of deposit
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Fair Value		1.8
Level 1 | Marketable Securities, Noncurrent | Corporate bonds
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Fair Value		277.5
Level 1 | Marketable Securities, Noncurrent | Corporate debt securities
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Fair Value				320.4
Level 1 | Marketable Securities, Noncurrent | Municipal bonds
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Fair Value		9.6		2.9
Level 1 | Marketable Securities, Noncurrent | Sovereign debt
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Fair Value		0.0		0.0
Level 1 | Marketable Securities, Noncurrent | U.S. government securities
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Fair Value		94.5		98.6
Level 1 | Convertible debt securities
Schedule of Available-for-sale Securities [Line Items]
Convertible debt securities, Fair Value	[2]	0.0		0.0
Level 1 | Agency bonds
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents, Fair Value		44.2	[3]	8.5	[4]
Level 1 | Certificates of deposit
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents, Fair Value		181.3	[3]	267.6	[4]
Level 1 | Commercial paper
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents, Fair Value		0.0	[3]	0.0	[4]
Level 1 | Corporate bonds
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents, Fair Value	[3]	8.7
Level 1 | Custody cash deposit
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents, Fair Value		22.5	[3]	2.1	[4]
Level 1 | Money market funds
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents, Fair Value		0.0	[3]	0.0	[4]
Level 1 | Municipal bonds
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents, Fair Value		5.0	[3]	5.0	[4]
Level 1 | U.S. government securities
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents, Fair Value		167.0	[3]	103.0	[4]
Level 2
Schedule of Available-for-sale Securities [Line Items]
Derivative contracts, Fair Value	[1]	(1.7)		1.6
Fair Value		658.7		712.6
Level 2 | Marketable Securities, Current
Schedule of Available-for-sale Securities [Line Items]
Mutual funds, Fair Value		0.0		0.0
Level 2 | Marketable Securities, Current | Agency bonds
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Fair Value		0.0		0.0
Level 2 | Marketable Securities, Current | Asset backed securities
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Fair Value		10.8		7.3
Level 2 | Marketable Securities, Current | Certificates of deposit
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Fair Value		0.0		0.0
Level 2 | Marketable Securities, Current | Commercial paper
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Fair Value		119.4		141.1
Level 2 | Marketable Securities, Current | Corporate bonds
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Fair Value		0.0
Level 2 | Marketable Securities, Current | Corporate debt securities
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Fair Value				0.0
Level 2 | Marketable Securities, Current | Municipal bonds
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Fair Value				0.0
Level 2 | Marketable Securities, Current | Sovereign debt
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Fair Value		19.6		20.1
Level 2 | Marketable Securities, Current | U.S. government securities
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Fair Value		0.0		0.0
Level 2 | Marketable Securities, Noncurrent | Agency bonds
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Fair Value		0.0		0.0
Level 2 | Marketable Securities, Noncurrent | Asset backed securities
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Fair Value		59.1		36.6
Level 2 | Marketable Securities, Noncurrent | Certificates of deposit
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Fair Value		0.0
Level 2 | Marketable Securities, Noncurrent | Corporate bonds
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Fair Value		0.0
Level 2 | Marketable Securities, Noncurrent | Corporate debt securities
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Fair Value				0.0
Level 2 | Marketable Securities, Noncurrent | Municipal bonds
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Fair Value		0.0		0.0
Level 2 | Marketable Securities, Noncurrent | Sovereign debt
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Fair Value		10.8		16.9
Level 2 | Marketable Securities, Noncurrent | U.S. government securities
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Fair Value		0.0		0.0
Level 2 | Convertible debt securities
Schedule of Available-for-sale Securities [Line Items]
Convertible debt securities, Fair Value	[2]	0.0		0.0
Level 2 | Agency bonds
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents, Fair Value		0.0	[3]	0.0	[4]
Level 2 | Certificates of deposit
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents, Fair Value		0.0	[3]	0.0	[4]
Level 2 | Commercial paper
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents, Fair Value		296.9	[3]	106.6	[4]
Level 2 | Corporate bonds
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents, Fair Value	[3]	0.0
Level 2 | Custody cash deposit
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents, Fair Value		0.0	[3]	0.0	[4]
Level 2 | Money market funds
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents, Fair Value		143.8	[3]	382.4	[4]
Level 2 | Municipal bonds
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents, Fair Value		0.0	[3]	0.0	[4]
Level 2 | U.S. government securities
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents, Fair Value		0.0	[3]	0.0	[4]
Level 3
Schedule of Available-for-sale Securities [Line Items]
Derivative contracts, Fair Value	[1]	1.2		0.3
Fair Value		8.6		3.7
Level 3 | Marketable Securities, Current
Schedule of Available-for-sale Securities [Line Items]
Mutual funds, Fair Value		0.0		0.0
Level 3 | Marketable Securities, Current | Agency bonds
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Fair Value		0.0		0.0
Level 3 | Marketable Securities, Current | Asset backed securities
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Fair Value		0.0		0.0
Level 3 | Marketable Securities, Current | Certificates of deposit
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Fair Value		0.0		0.0
Level 3 | Marketable Securities, Current | Commercial paper
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Fair Value		0.0		0.0
Level 3 | Marketable Securities, Current | Corporate bonds
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Fair Value		0.0
Level 3 | Marketable Securities, Current | Corporate debt securities
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Fair Value				0.0
Level 3 | Marketable Securities, Current | Municipal bonds
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Fair Value				0.0
Level 3 | Marketable Securities, Current | Sovereign debt
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Fair Value		0.0
Level 3 | Marketable Securities, Current | U.S. government securities
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Fair Value		0.0		0.0
Level 3 | Marketable Securities, Noncurrent | Agency bonds
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Fair Value		0.0		0.0
Level 3 | Marketable Securities, Noncurrent | Asset backed securities
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Fair Value		0.0		0.0
Level 3 | Marketable Securities, Noncurrent | Certificates of deposit
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Fair Value		0.0
Level 3 | Marketable Securities, Noncurrent | Corporate bonds
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Fair Value		0.0
Level 3 | Marketable Securities, Noncurrent | Corporate debt securities
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Fair Value				0.0
Level 3 | Marketable Securities, Noncurrent | Municipal bonds
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Fair Value		0.0		0.0
Level 3 | Marketable Securities, Noncurrent | Sovereign debt
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Fair Value		0.0		0.0
Level 3 | Marketable Securities, Noncurrent | U.S. government securities
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Fair Value		0.0		0.0
Level 3 | Convertible debt securities
Schedule of Available-for-sale Securities [Line Items]
Convertible debt securities, Fair Value	[2]	7.4		3.4
Level 3 | Agency bonds
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents, Fair Value		0.0	[3]	0.0	[4]
Level 3 | Certificates of deposit
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents, Fair Value		0.0	[3]	0.0	[4]
Level 3 | Commercial paper
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents, Fair Value		0.0	[3]	0.0	[4]
Level 3 | Corporate bonds
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents, Fair Value	[3]	0.0
Level 3 | Custody cash deposit
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents, Fair Value		0.0	[3]	0.0	[4]
Level 3 | Money market funds
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents, Fair Value		0.0	[3]	0.0	[4]
Level 3 | Municipal bonds
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents, Fair Value		0.0	[3]	0.0	[4]
Level 3 | U.S. government securities
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents, Fair Value		$ 0.0	[3]	$ 0.0	[4]

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

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

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

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