Financial Instruments - Cost and Fair Value of Financial Instruments (Details) - USD ($) $ in Millions		Jan. 31, 2016		Jan. 31, 2015		Jan. 31, 2014	Jan. 31, 2013
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents		$ 1,353.0		$ 1,410.6		$ 1,853.0	$ 1,612.2
Derivative Instruments And Hedges at Amortized Cost		1.5	[1]	3.5	[2]
Unrealized Gain on Foreign Currency Derivatives		7.8	[1]	19.5	[2]
Unrealized Loss on Foreign Currency Derivatives		(7.4)	[1]	(7.0)	[2]
Derivative Contracts, Fair Value		1.9	[1]	16.0	[2]
Amortized Cost Securities		2,310.6		1,592.6
Unrealized Gain on Securities		11.1		26.6
Unrealized Loss on Securities		(11.0)		(9.4)
Total		2,310.7		1,609.8
Marketable Securities, Current
Schedule of Available-for-sale Securities [Line Items]
Trading Securities, Cost		38.8		36.9
Trading Securities, Unrealized Holding Gain		0.4		3.4
Trading Securities, Unrealized Holding Loss		(1.2)		0.0
Trading Securities		38.0		40.3
Other Assets
Schedule of Available-for-sale Securities [Line Items]
Convertible Debt Securities, Amortized Cost		2.5	[3]	4.7	[4]
Convertible Debt Securities, Unrealized Gains		2.0	[3]	2.5	[4]
Convertible Debt Securities, Unrealized Losses		(1.1)	[3]	(2.1)	[4]
Convertible Debt Securities, Fair Value		3.4	[3]	5.1	[4]
Level 1
Schedule of Available-for-sale Securities [Line Items]
Derivative Contracts, Fair Value		0.0	[1]	0.0	[2]
Total		1,594.4		1,042.0
Level 1 | Marketable Securities, Current
Schedule of Available-for-sale Securities [Line Items]
Trading Securities		38.0		40.3
Level 1 | Other Assets
Schedule of Available-for-sale Securities [Line Items]
Convertible Debt Securities, Fair Value		0.0	[3]	0.0	[4]
Level 2
Schedule of Available-for-sale Securities [Line Items]
Derivative Contracts, Fair Value		1.6	[1]	15.1	[2]
Total		712.6		561.8
Level 2 | Marketable Securities, Current
Schedule of Available-for-sale Securities [Line Items]
Trading Securities		0.0		0.0
Level 2 | Other Assets
Schedule of Available-for-sale Securities [Line Items]
Convertible Debt Securities, Fair Value		0.0	[3]	0.0	[4]
Level 3
Schedule of Available-for-sale Securities [Line Items]
Derivative Contracts, Fair Value		0.3	[1]	0.9	[2]
Total		3.7		6.0
Level 3 | Marketable Securities, Current
Schedule of Available-for-sale Securities [Line Items]
Trading Securities		0.0		0.0
Level 3 | Other Assets
Schedule of Available-for-sale Securities [Line Items]
Convertible Debt Securities, Fair Value		3.4	[3]	5.1	[4]
Agency bonds | Marketable Securities, Current
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost				37.9
Available-for-sale Debt Securities, Accumulated Gross Unrealized Gain				0.0
Available-for-sale Debt Securities, Accumulated Gross Unrealized Loss				0.0
Available-for-sale Securities, Fair Value				37.9
Agency bonds | Marketable Securities, Noncurrent
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost		56.8		50.6
Available-for-sale Debt Securities, Accumulated Gross Unrealized Gain		0.1		0.2
Available-for-sale Debt Securities, Accumulated Gross Unrealized Loss		0.0		0.0
Available-for-sale Securities, Fair Value		56.9		50.8
Agency bonds | Level 1 | Marketable Securities, Current
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair Value				37.9
Agency bonds | Level 1 | Marketable Securities, Noncurrent
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair Value		56.9		50.8
Agency bonds | Level 2 | Marketable Securities, Current
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair Value				0.0
Agency bonds | Level 2 | Marketable Securities, Noncurrent
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair Value		0.0		0.0
Agency bonds | Level 3 | Marketable Securities, Current
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair Value				0.0
Agency bonds | Level 3 | Marketable Securities, Noncurrent
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair Value		0.0		0.0
Asset backed securities | Marketable Securities, Current
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost		7.3
Available-for-sale Debt Securities, Accumulated Gross Unrealized Gain		0.0
Available-for-sale Debt Securities, Accumulated Gross Unrealized Loss		0.0
Available-for-sale Securities, Fair Value		7.3
Asset backed securities | Marketable Securities, Noncurrent
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost		36.5
Available-for-sale Debt Securities, Accumulated Gross Unrealized Gain		0.1
Available-for-sale Debt Securities, Accumulated Gross Unrealized Loss		0.0
Available-for-sale Securities, Fair Value		36.6
Asset backed securities | Level 1 | Marketable Securities, Current
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair Value		0.0
Asset backed securities | Level 1 | Marketable Securities, Noncurrent
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair Value		0.0
Asset backed securities | Level 2 | Marketable Securities, Current
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair Value		7.3
Asset backed securities | Level 2 | Marketable Securities, Noncurrent
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair Value		36.6
Asset backed securities | Level 3 | Marketable Securities, Current
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair Value		0.0
Asset backed securities | Level 3 | Marketable Securities, Noncurrent
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair Value		0.0
Certificates of deposit | Marketable Securities, Current
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost		190.3		101.9
Available-for-sale Debt Securities, Accumulated Gross Unrealized Gain		0.0		0.0
Available-for-sale Debt Securities, Accumulated Gross Unrealized Loss		0.0		0.0
Available-for-sale Securities, Fair Value		190.3		101.9
Certificates of deposit | Level 1 | Marketable Securities, Current
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair Value		190.3		101.9
Certificates of deposit | Level 2 | Marketable Securities, Current
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair Value		0.0		0.0
Certificates of deposit | Level 3 | Marketable Securities, Current
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair Value		0.0		0.0
Commercial paper | Marketable Securities, Current
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost		141.1		258.4
Available-for-sale Debt Securities, Accumulated Gross Unrealized Gain		0.0		0.0
Available-for-sale Debt Securities, Accumulated Gross Unrealized Loss		0.0		0.0
Available-for-sale Securities, Fair Value		141.1		258.4
Commercial paper | Level 1 | Marketable Securities, Current
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair Value		0.0		0.0
Commercial paper | Level 2 | Marketable Securities, Current
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair Value		141.1		258.4
Commercial paper | Level 3 | Marketable Securities, Current
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair Value		0.0		0.0
Corporate debt securities | Marketable Securities, Current
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost		377.1		148.0
Available-for-sale Debt Securities, Accumulated Gross Unrealized Gain		0.1		0.1
Available-for-sale Debt Securities, Accumulated Gross Unrealized Loss		(0.3)		(0.1)
Available-for-sale Securities, Fair Value		376.9		148.0
Corporate debt securities | Marketable Securities, Noncurrent
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost		320.9		199.4
Available-for-sale Debt Securities, Accumulated Gross Unrealized Gain		0.3		0.6
Available-for-sale Debt Securities, Accumulated Gross Unrealized Loss		(0.8)		(0.2)
Available-for-sale Securities, Fair Value		320.4		199.8
Corporate debt securities | Level 1 | Marketable Securities, Current
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair Value		376.9		148.0
Corporate debt securities | Level 1 | Marketable Securities, Noncurrent
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair Value		320.4		199.8
Corporate debt securities | Level 2 | Marketable Securities, Current
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair Value		0.0		0.0
Corporate debt securities | Level 2 | Marketable Securities, Noncurrent
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair Value		0.0		0.0
Corporate debt securities | Level 3 | Marketable Securities, Current
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair Value		0.0		0.0
Corporate debt securities | Level 3 | Marketable Securities, Noncurrent
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair Value		0.0		0.0
Municipal bonds | Marketable Securities, Current
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost		9.7		29.2
Available-for-sale Debt Securities, Accumulated Gross Unrealized Gain		0.0		0.1
Available-for-sale Debt Securities, Accumulated Gross Unrealized Loss		0.0		0.0
Available-for-sale Securities, Fair Value		9.7		29.3
Municipal bonds | Marketable Securities, Noncurrent
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost		2.9		13.3
Available-for-sale Debt Securities, Accumulated Gross Unrealized Gain		0.0		0.1
Available-for-sale Debt Securities, Accumulated Gross Unrealized Loss		0.0		0.0
Available-for-sale Securities, Fair Value		2.9		13.4
Municipal bonds | Level 1 | Marketable Securities, Current
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair Value		9.7		29.3
Municipal bonds | Level 1 | Marketable Securities, Noncurrent
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair Value		2.9		13.4
Municipal bonds | Level 2 | Marketable Securities, Current
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair Value		0.0		0.0
Municipal bonds | Level 2 | Marketable Securities, Noncurrent
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair Value		0.0		0.0
Municipal bonds | Level 3 | Marketable Securities, Current
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair Value		0.0		0.0
Municipal bonds | Level 3 | Marketable Securities, Noncurrent
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair Value		0.0		0.0
Sovereign debt | Marketable Securities, Current
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost		20.1
Available-for-sale Debt Securities, Accumulated Gross Unrealized Gain		0.0
Available-for-sale Debt Securities, Accumulated Gross Unrealized Loss		0.0
Available-for-sale Securities, Fair Value		20.1
Sovereign debt | Marketable Securities, Noncurrent
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost		16.9
Available-for-sale Debt Securities, Accumulated Gross Unrealized Gain		0.0
Available-for-sale Debt Securities, Accumulated Gross Unrealized Loss		0.0
Available-for-sale Securities, Fair Value		16.9
Sovereign debt | Level 1 | Marketable Securities, Current
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair Value		0.0
Sovereign debt | Level 1 | Marketable Securities, Noncurrent
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair Value		0.0
Sovereign debt | Level 2 | Marketable Securities, Current
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair Value		20.1
Sovereign debt | Level 2 | Marketable Securities, Noncurrent
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair Value		16.9
Sovereign debt | Level 3 | Marketable Securities, Current
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair Value		0.0
Sovereign debt | Level 3 | Marketable Securities, Noncurrent
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair Value		0.0
U.S. government agency securities | Marketable Securities, Current
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost		40.0
Available-for-sale Debt Securities, Accumulated Gross Unrealized Gain		0.0
Available-for-sale Debt Securities, Accumulated Gross Unrealized Loss		(0.1)
Available-for-sale Securities, Fair Value		39.9
U.S. government agency securities | Marketable Securities, Noncurrent
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost		98.4		8.9
Available-for-sale Debt Securities, Accumulated Gross Unrealized Gain		0.3		0.1
Available-for-sale Debt Securities, Accumulated Gross Unrealized Loss		(0.1)		0.0
Available-for-sale Securities, Fair Value		98.6		9.0
U.S. government agency securities | Level 1 | Marketable Securities, Current
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair Value		39.9
U.S. government agency securities | Level 1 | Marketable Securities, Noncurrent
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair Value		98.6		9.0
U.S. government agency securities | Level 2 | Marketable Securities, Current
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair Value		0.0
U.S. government agency securities | Level 2 | Marketable Securities, Noncurrent
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair Value		0.0		0.0
U.S. government agency securities | Level 3 | Marketable Securities, Current
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair Value		0.0
U.S. government agency securities | Level 3 | Marketable Securities, Noncurrent
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair Value		0.0		0.0
U.S. treasury bills | Marketable Securities, Current
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost		74.6
Available-for-sale Debt Securities, Accumulated Gross Unrealized Gain		0.0
Available-for-sale Debt Securities, Accumulated Gross Unrealized Loss		0.0
Available-for-sale Securities, Fair Value		74.6
U.S. treasury bills | Level 1 | Marketable Securities, Current
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair Value		74.6
U.S. treasury bills | Level 2 | Marketable Securities, Current
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair Value		0.0
U.S. treasury bills | Level 3 | Marketable Securities, Current
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair Value		0.0
Agency bonds
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents	[5]	8.5
Cash and Cash Equivalents, Fair Value Disclosure	[5]	8.5
Agency bonds | Level 1
Schedule of Available-for-sale Securities [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure	[5]	8.5
Agency bonds | Level 2
Schedule of Available-for-sale Securities [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure	[5]	0.0
Agency bonds | Level 3
Schedule of Available-for-sale Securities [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure	[5]	0.0
Certificates of deposit
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents		267.6	[5]	258.6	[6]
Cash and Cash Equivalents, Fair Value Disclosure		267.6	[5]	258.6	[6]
Certificates of deposit | Level 1
Schedule of Available-for-sale Securities [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure		267.6	[5]	258.6	[6]
Certificates of deposit | Level 2
Schedule of Available-for-sale Securities [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure		0.0	[5]	0.0	[6]
Certificates of deposit | Level 3
Schedule of Available-for-sale Securities [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure		0.0	[5]	0.0
Commercial paper
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents		106.6	[5]	161.0	[6]
Cash and Cash Equivalents, Fair Value Disclosure		106.6	[5]	161.0	[6]
Commercial paper | Level 1
Schedule of Available-for-sale Securities [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure		0.0	[5]	0.0	[6]
Commercial paper | Level 2
Schedule of Available-for-sale Securities [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure		106.6	[5]	161.0	[6]
Commercial paper | Level 3
Schedule of Available-for-sale Securities [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure		0.0	[5]	0.0
Corporate bond
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents	[6]			11.5
Cash and Cash Equivalents, Fair Value Disclosure	[6]			11.5
Corporate bond | Level 1
Schedule of Available-for-sale Securities [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure	[6]			11.5
Corporate bond | Level 2
Schedule of Available-for-sale Securities [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure	[6]			0.0
Corporate bond | Level 3
Schedule of Available-for-sale Securities [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure				0.0
Custody cash deposit
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents		2.1	[5]	141.5	[6]
Cash and Cash Equivalents, Fair Value Disclosure		2.1	[5]	141.5	[6]
Custody cash deposit | Level 1
Schedule of Available-for-sale Securities [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure		2.1	[5]	141.5	[6]
Custody cash deposit | Level 2
Schedule of Available-for-sale Securities [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure		0.0	[5]	0.0	[6]
Custody cash deposit | Level 3
Schedule of Available-for-sale Securities [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure		0.0	[5]	0.0
Money market funds
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents		382.4	[5]	127.3	[6]
Cash and Cash Equivalents, Fair Value Disclosure		382.4	[5]	127.3	[6]
Money market funds | Level 1
Schedule of Available-for-sale Securities [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure		0.0	[5]	0.0	[6]
Money market funds | Level 2
Schedule of Available-for-sale Securities [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure		382.4	[5]	127.3	[6]
Money market funds | Level 3
Schedule of Available-for-sale Securities [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure		0.0	[5]	$ 0.0
Municipal bonds
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents	[5]	5.0
Cash and Cash Equivalents, Fair Value Disclosure	[5]	5.0
Municipal bonds | Level 1
Schedule of Available-for-sale Securities [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure	[5]	5.0
Municipal bonds | Level 2
Schedule of Available-for-sale Securities [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure	[5]	0.0
Municipal bonds | Level 3
Schedule of Available-for-sale Securities [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure	[5]	0.0
U.S. treasury bills
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents	[5]	103.0
Cash and Cash Equivalents, Fair Value Disclosure	[5]	103.0
U.S. treasury bills | Level 1
Schedule of Available-for-sale Securities [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure	[5]	103.0
U.S. treasury bills | Level 2
Schedule of Available-for-sale Securities [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure	[5]	0.0
U.S. treasury bills | Level 3
Schedule of Available-for-sale Securities [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure	[5]	$ 0.0

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

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

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

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

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

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