Financial Instruments Cost and Fair Value of Financial Instruments (Details) - USD ($) $ in Millions		Apr. 30, 2017		Jan. 31, 2017		Apr. 30, 2016	Jan. 31, 2016
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents		$ 1,340.2		$ 1,213.1		$ 1,223.4	$ 1,353.0
Derivative contracts, Amortized Cost		5.1	[1]	2.2	[2]
Derivative contracts, Gross unrealized gains		5.1	[1]	12.3	[2]
Derivative contracts, Gross unrealized losses		(1.8)	[1]	(11.7)	[2]
Derivative contracts, Fair Value		8.4	[1]	2.8	[2]
Amortized Cost		1,655.0		1,903.5
Gross unrealized gains		12.6		17.4
Gross unrealized losses		(3.6)		(13.6)
Fair Value		1,664.0		1,907.3
Marketable Securities, Current
Schedule of Available-for-sale Securities [Line Items]
Mutual funds, Amortized Cost		48.3		44.8
Mutual funds, Gross unrealized gains		4.2		2.5
Mutual funds, Gross unrealized losses		0.0		0.0
Mutual funds, Fair Value		52.5		47.3
Marketable Securities, Current | Agency bonds
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Amortized Cost		7.5		13.2
Marketable securities, Gross unrealized gains		0.0		0.0
Marketable securities, Gross unrealized losses		0.0
Marketable securities, Fair Value		7.5		13.2
Marketable Securities, Current | Asset backed securities
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Amortized Cost		30.9		19.6
Marketable securities, Gross unrealized gains		0.0		0.0
Marketable securities, Gross unrealized losses		0.0		0.0
Marketable securities, Fair Value		30.9		19.6
Marketable Securities, Current | Certificates of deposit
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Amortized Cost		19.7		157.3
Marketable securities, Gross unrealized gains		0.0		0.0
Marketable securities, Gross unrealized losses		0.0		0.0
Marketable securities, Fair Value		19.7		157.3
Marketable Securities, Current | Commercial paper
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Amortized Cost		81.3		109.2
Marketable securities, Gross unrealized gains		0.0		0.0
Marketable securities, Gross unrealized losses		0.0		0.0
Marketable securities, Fair Value		81.3		109.2
Marketable Securities, Current | Corporate debt securities
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Amortized Cost		204.9		234.7
Marketable securities, Gross unrealized gains		0.1		0.0
Marketable securities, Gross unrealized losses		(0.1)		(0.2)
Marketable securities, Fair Value		204.9		234.5
Marketable Securities, Current | Municipal bonds
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Amortized Cost		36.9		43.4
Marketable securities, Gross unrealized gains		0.0		0.0
Marketable securities, Gross unrealized losses		0.0		0.0
Marketable securities, Fair Value		36.9		43.4
Marketable Securities, Current | Sovereign debt
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Amortized Cost		12.0		30.0
Marketable securities, Gross unrealized gains		0.0		0.0
Marketable securities, Gross unrealized losses		0.0		0.0
Marketable securities, Fair Value		12.0		30.0
Marketable Securities, Current | U.S. government securities
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Amortized Cost		25.4		32.3
Marketable securities, Gross unrealized gains		0.0		0.0
Marketable securities, Gross unrealized losses		0.0		0.0
Marketable securities, Fair Value		25.4		32.3
Marketable Securities, Noncurrent | Agency bonds
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Amortized Cost		2.6		7.1
Marketable securities, Gross unrealized gains		0.0		0.0
Marketable securities, Gross unrealized losses		0.0		0.0
Marketable securities, Fair Value		2.6		7.1
Marketable Securities, Noncurrent | Asset backed securities
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Amortized Cost		54.9		65.8
Marketable securities, Gross unrealized gains		0.0		0.1
Marketable securities, Gross unrealized losses		(0.1)		0.0
Marketable securities, Fair Value		54.8		65.9
Marketable Securities, Noncurrent | Corporate debt securities
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Amortized Cost		143.1		172.1
Marketable securities, Gross unrealized gains		0.2		0.1
Marketable securities, Gross unrealized losses		0.0		(0.1)
Marketable securities, Fair Value		143.3		172.1
Marketable Securities, Noncurrent | Municipal bonds
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Amortized Cost		7.6		10.7
Marketable securities, Gross unrealized gains		0.0		0.0
Marketable securities, Gross unrealized losses		0.0		0.0
Marketable securities, Fair Value		7.6		10.7
Marketable Securities, Noncurrent | Sovereign debt
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Amortized Cost				1.5
Marketable securities, Gross unrealized gains				0.0
Marketable securities, Gross unrealized losses				0.0
Marketable securities, Fair Value				1.5
Marketable Securities, Noncurrent | U.S. government securities
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Amortized Cost		56.1		48.8
Marketable securities, Gross unrealized gains		0.0		0.1
Marketable securities, Gross unrealized losses		0.0		0.0
Marketable securities, Fair Value		56.1		48.9
Convertible debt securities
Schedule of Available-for-sale Securities [Line Items]
Convertible debt securities, Amortized Cost		8.9	[3]	4.9	[4]
Convertible debt securities, Gross unrealized gains		3.0	[3]	2.3	[4]
Convertible debt securities, Gross unrealized losses		(1.6)	[3]	(1.6)	[4]
Convertible debt securities, Fair Value		10.3	[3]	5.6	[4]
Agency bonds
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents		17.0	[5]	6.0	[6]
Cash equivalents, Fair Value		17.0	[5]	6.0	[6]
Asset backed securities
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents	[5]	2.5
Cash equivalents, Fair Value	[5]	2.5
Certificates of deposit
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents		61.0	[5]	63.1	[6]
Cash equivalents, Fair Value		61.0	[5]	63.1	[6]
Corporate debt securities
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents		10.2	[5]	40.2	[6]
Cash equivalents, Fair Value		10.2	[5]	40.2	[6]
Commercial paper
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents		212.0	[5]	207.4	[6]
Cash equivalents, Fair Value		212.0	[5]	207.4	[6]
Custody cash deposit
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents		27.0	[5]	3.2	[6]
Cash equivalents, Fair Value		27.0	[5]	3.2	[6]
Municipal bonds
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents		5.0	[5]	5.0	[6]
Cash equivalents, Fair Value		5.0	[5]	5.0	[6]
Money Market funds
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents		542.6	[5]	256.5
Cash equivalents, Fair Value		542.6	[5]	256.5
Sovereign debt
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents	[6]			15.0
Cash equivalents, Fair Value	[6]			15.0
U.S. government securities
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents		32.5	[5]	309.5	[6]
Cash equivalents, Fair Value		32.5	[5]	309.5	[6]
Level 1
Schedule of Available-for-sale Securities [Line Items]
Derivative contracts, Fair Value		0.0	[1]	0.0	[2]
Fair Value		709.2		1,193.8
Level 1 | Marketable Securities, Current
Schedule of Available-for-sale Securities [Line Items]
Mutual funds, Fair Value		52.5		47.3
Level 1 | Marketable Securities, Current | Agency bonds
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Fair Value		7.5		13.2
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		19.7		157.3
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 debt securities
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Fair Value		204.9		234.5
Level 1 | Marketable Securities, Current | Municipal bonds
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Fair Value		36.9		43.4
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		25.4		32.3
Level 1 | Marketable Securities, Noncurrent | Agency bonds
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Fair Value		2.6		7.1
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 | Corporate debt securities
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Fair Value		143.3		172.1
Level 1 | Marketable Securities, Noncurrent | Municipal bonds
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Fair Value		7.6		10.7
Level 1 | Marketable Securities, Noncurrent | Sovereign debt
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Fair Value				0.0
Level 1 | Marketable Securities, Noncurrent | U.S. government securities
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Fair Value		56.1		48.9
Level 1 | Convertible debt securities
Schedule of Available-for-sale Securities [Line Items]
Convertible debt securities, Fair Value		0.0	[3]	0.0	[4]
Level 1 | Agency bonds
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents, Fair Value		17.0	[5]	6.0	[6]
Level 1 | Asset backed securities
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents, Fair Value	[5]	0.0
Level 1 | Certificates of deposit
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents, Fair Value		61.0	[5]	63.1	[6]
Level 1 | Corporate debt securities
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents, Fair Value		10.2	[5]	40.2	[6]
Level 1 | Commercial paper
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents, Fair Value		0.0	[5]	0.0	[6]
Level 1 | Custody cash deposit
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents, Fair Value		27.0	[5]	3.2	[6]
Level 1 | Municipal bonds
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents, Fair Value		5.0	[5]	5.0	[6]
Level 1 | Money Market funds
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents, Fair Value		0.0	[5]	0.0
Level 1 | Sovereign debt
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents, Fair Value	[6]			0.0
Level 1 | U.S. government securities
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents, Fair Value		32.5	[5]	309.5	[6]
Level 2
Schedule of Available-for-sale Securities [Line Items]
Derivative contracts, Fair Value		4.5	[1]	1.5	[2]
Fair Value		940.6		706.6
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		30.9		19.6
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		81.3		109.2
Level 2 | Marketable Securities, Current | Corporate debt securities
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Fair Value		0.0		0.0
Level 2 | Marketable Securities, Current | Municipal bonds
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Fair Value		0.0		0.0
Level 2 | Marketable Securities, Current | Sovereign debt
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Fair Value		12.0		30.0
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		54.8		65.9
Level 2 | Marketable Securities, Noncurrent | Corporate debt securities
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Fair Value		0.0		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				1.5
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		0.0	[3]	0.0	[4]
Level 2 | Agency bonds
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents, Fair Value		0.0	[5]	0.0	[6]
Level 2 | Asset backed securities
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents, Fair Value	[5]	2.5
Level 2 | Certificates of deposit
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents, Fair Value		0.0	[5]	0.0	[6]
Level 2 | Corporate debt securities
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents, Fair Value		0.0	[5]	0.0	[6]
Level 2 | Commercial paper
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents, Fair Value		212.0	[5]	207.4	[6]
Level 2 | Custody cash deposit
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents, Fair Value		0.0	[5]	0.0	[6]
Level 2 | Municipal bonds
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents, Fair Value		0.0	[5]	0.0	[6]
Level 2 | Money Market funds
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents, Fair Value		542.6	[5]	256.5
Level 2 | Sovereign debt
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents, Fair Value	[6]			15.0
Level 2 | U.S. government securities
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents, Fair Value		0.0	[5]	0.0	[6]
Level 3
Schedule of Available-for-sale Securities [Line Items]
Derivative contracts, Fair Value		3.9	[1]	1.3	[2]
Fair Value		14.2		6.9
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 debt securities
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Fair Value		0.0		0.0
Level 3 | Marketable Securities, Current | Municipal bonds
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Fair Value		0.0		0.0
Level 3 | Marketable Securities, Current | Sovereign debt
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Fair Value		0.0		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 | Corporate debt securities
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Fair Value		0.0		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
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		10.3	[3]	5.6	[4]
Level 3 | Agency bonds
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents, Fair Value		0.0	[5]	0.0	[6]
Level 3 | Asset backed securities
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents, Fair Value	[5]	0.0
Level 3 | Certificates of deposit
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents, Fair Value		0.0	[5]	0.0	[6]
Level 3 | Corporate debt securities
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents, Fair Value		0.0	[5]	0.0	[6]
Level 3 | Commercial paper
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents, Fair Value		0.0	[5]	0.0	[6]
Level 3 | Custody cash deposit
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents, Fair Value		0.0	[5]	0.0	[6]
Level 3 | Municipal bonds
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents, Fair Value		0.0	[5]	0.0	[6]
Level 3 | Money Market funds
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents, Fair Value		0.0	[5]	0.0
Level 3 | Sovereign debt
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents, Fair Value	[6]			0.0
Level 3 | U.S. government securities
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents, Fair Value		$ 0.0	[5]	$ 0.0	[6]

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

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

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

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

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

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