Financial Instruments - Cost and Fair Value of Financial Instruments (Details) - USD ($) $ in Millions		Jan. 31, 2017		Jan. 31, 2016		Jan. 31, 2015	Jan. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents		$ 1,213.1		$ 1,353.0		$ 1,410.6	$ 1,853.0
Derivative Instruments And Hedges at Amortized Cost		2.2		1.5	[1]
Unrealized Gain on Foreign Currency Derivatives		12.3		7.8	[1]
Unrealized Loss on Foreign Currency Derivatives		(11.7)		(7.4)	[1]
Derivative Contracts, Fair Value		2.8		1.9	[1]
Amortized Cost Securities		1,903.5		2,310.6
Unrealized Gain on Securities		17.4		11.1
Unrealized Loss on Securities		(13.6)		(11.0)
Total		1,907.3		2,310.7
Marketable Securities, Current
Schedule of Available-for-sale Securities [Line Items]
Trading Securities, Cost		44.8		38.8
Trading Securities, Unrealized Holding Gain		2.5		0.4
Trading Securities, Unrealized Holding Loss		0.0		(1.2)
Trading Securities		47.3		38.0
Convertible Debt Securities
Schedule of Available-for-sale Securities [Line Items]
Convertible Debt Securities, Amortized Cost		4.9	[2]	2.5	[3]
Convertible Debt Securities, Unrealized Gains		2.3	[2]	2.0	[3]
Convertible Debt Securities, Unrealized Losses		(1.6)	[2]	(1.1)	[3]
Convertible Debt Securities, Fair Value		5.6	[2]	3.4	[3]
Level 1
Schedule of Available-for-sale Securities [Line Items]
Derivative Contracts, Fair Value		0.0		0.0	[1]
Total		1,193.8		1,594.4
Level 1 | Marketable Securities, Current
Schedule of Available-for-sale Securities [Line Items]
Trading Securities		47.3		38.0
Level 1 | Convertible Debt Securities
Schedule of Available-for-sale Securities [Line Items]
Convertible Debt Securities, Fair Value		0.0	[2]	0.0	[3]
Level 2
Schedule of Available-for-sale Securities [Line Items]
Derivative Contracts, Fair Value		1.5		1.6	[1]
Total		706.6		712.6
Level 2 | Marketable Securities, Current
Schedule of Available-for-sale Securities [Line Items]
Trading Securities		0.0		0.0
Level 2 | Convertible Debt Securities
Schedule of Available-for-sale Securities [Line Items]
Convertible Debt Securities, Fair Value		0.0	[2]	0.0	[3]
Level 3
Schedule of Available-for-sale Securities [Line Items]
Derivative Contracts, Fair Value		1.3		0.3	[1]
Total		6.9		3.7
Level 3 | Marketable Securities, Current
Schedule of Available-for-sale Securities [Line Items]
Trading Securities		0.0		0.0
Level 3 | Convertible Debt Securities
Schedule of Available-for-sale Securities [Line Items]
Convertible Debt Securities, Fair Value		5.6	[2]	3.4	[3]
Agency bonds | Marketable Securities, Current
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost		13.2		40.0
Available-for-sale, Gross unrealized gains		0.0		0.0
Available-for-sale, Gross unrealized losses				(0.1)
Available-for-sale Securities, Fair Value		13.2		39.9
Agency bonds | Marketable Securities, Noncurrent
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost		7.1		56.8
Available-for-sale, Gross unrealized gains		0.0		0.1
Available-for-sale, Gross unrealized losses		0.0		0.0
Available-for-sale Securities, Fair Value		7.1		56.9
Agency bonds | Level 1 | Marketable Securities, Current
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair Value		13.2		39.9
Agency bonds | Level 1 | Marketable Securities, Noncurrent
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair Value		7.1		56.9
Agency bonds | Level 2 | Marketable Securities, Current
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair Value		0.0		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		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		19.6		7.3
Available-for-sale, Gross unrealized gains		0.0		0.0
Available-for-sale, Gross unrealized losses		0.0		0.0
Available-for-sale Securities, Fair Value		19.6		7.3
Asset backed securities | Marketable Securities, Noncurrent
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost		65.8		36.5
Available-for-sale, Gross unrealized gains		0.1		0.1
Available-for-sale, Gross unrealized losses		0.0		0.0
Available-for-sale Securities, Fair Value		65.9		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		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		0.0
Asset backed securities | Level 2 | Marketable Securities, Current
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair Value		19.6		7.3
Asset backed securities | Level 2 | Marketable Securities, Noncurrent
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair Value		65.9		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		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		0.0
Certificates of deposit | Marketable Securities, Current
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost		157.3		190.3
Available-for-sale, Gross unrealized gains		0.0		0.0
Available-for-sale, Gross unrealized losses		0.0		0.0
Available-for-sale Securities, Fair Value		157.3		190.3
Certificates of deposit | Level 1 | Marketable Securities, Current
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair Value		157.3		190.3
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		109.2		141.1
Available-for-sale, Gross unrealized gains		0.0		0.0
Available-for-sale, Gross unrealized losses		0.0		0.0
Available-for-sale Securities, Fair Value		109.2		141.1
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		109.2		141.1
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		234.7		377.1
Available-for-sale, Gross unrealized gains		0.0		0.1
Available-for-sale, Gross unrealized losses		(0.2)		(0.3)
Available-for-sale Securities, Fair Value		234.5		376.9
Corporate debt securities | Marketable Securities, Noncurrent
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost		172.1		320.9
Available-for-sale, Gross unrealized gains		0.1		0.3
Available-for-sale, Gross unrealized losses		(0.1)		(0.8)
Available-for-sale Securities, Fair Value		172.1		320.4
Corporate debt securities | Level 1 | Marketable Securities, Current
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair Value		234.5		376.9
Corporate debt securities | Level 1 | Marketable Securities, Noncurrent
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair Value		172.1		320.4
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		43.4		9.7
Available-for-sale, Gross unrealized gains		0.0		0.0
Available-for-sale, Gross unrealized losses		0.0		0.0
Available-for-sale Securities, Fair Value		43.4		9.7
Municipal bonds | Marketable Securities, Noncurrent
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost		10.7		2.9
Available-for-sale, Gross unrealized gains		0.0		0.0
Available-for-sale, Gross unrealized losses		0.0		0.0
Available-for-sale Securities, Fair Value		10.7		2.9
Municipal bonds | Level 1 | Marketable Securities, Current
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair Value		43.4		9.7
Municipal bonds | Level 1 | Marketable Securities, Noncurrent
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair Value		10.7		2.9
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		30.0		20.1
Available-for-sale, Gross unrealized gains		0.0		0.0
Available-for-sale, Gross unrealized losses		0.0		0.0
Available-for-sale Securities, Fair Value		30.0		20.1
Sovereign debt | Marketable Securities, Noncurrent
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost		1.5		16.9
Available-for-sale, Gross unrealized gains		0.0		0.0
Available-for-sale, Gross unrealized losses		0.0		0.0
Available-for-sale Securities, Fair Value		1.5		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		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		0.0
Sovereign debt | Level 2 | Marketable Securities, Current
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair Value		30.0		20.1
Sovereign debt | Level 2 | Marketable Securities, Noncurrent
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair Value		1.5		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		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		0.0
U.S. government securities | Marketable Securities, Current
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost		32.3		74.6
Available-for-sale, Gross unrealized gains		0.0		0.0
Available-for-sale, Gross unrealized losses		0.0		0.0
Available-for-sale Securities, Fair Value		32.3		74.6
U.S. government securities | Marketable Securities, Noncurrent
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost		48.8		98.4
Available-for-sale, Gross unrealized gains		0.1		0.3
Available-for-sale, Gross unrealized losses		0.0		(0.1)
Available-for-sale Securities, Fair Value		48.9		98.6
U.S. government securities | Level 1 | Marketable Securities, Current
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair Value		32.3		74.6
U.S. government securities | Level 1 | Marketable Securities, Noncurrent
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair Value		48.9		98.6
U.S. government securities | Level 2 | Marketable Securities, Current
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair Value		0.0		0.0
U.S. government 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 securities | Level 3 | Marketable Securities, Current
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair Value		0.0		0.0
U.S. government securities | Level 3 | Marketable Securities, Noncurrent
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair Value		0.0		0.0
Agency bonds
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents	[4]	6.0		8.5
Cash and Cash Equivalents, Fair Value Disclosure	[4]	6.0		8.5
Agency bonds | Level 1
Schedule of Available-for-sale Securities [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure	[4]	6.0		8.5
Agency bonds | Level 2
Schedule of Available-for-sale Securities [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure	[4]	0.0		0.0
Agency bonds | Level 3
Schedule of Available-for-sale Securities [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure	[4]	0.0		0.0
Certificates of deposit
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents		63.1	[4]	267.6	[5]
Cash and Cash Equivalents, Fair Value Disclosure		63.1	[4]	267.6	[5]
Certificates of deposit | Level 1
Schedule of Available-for-sale Securities [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure		63.1	[4]	267.6	[5]
Certificates of deposit | Level 2
Schedule of Available-for-sale Securities [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure		0.0	[4]	0.0	[5]
Certificates of deposit | Level 3
Schedule of Available-for-sale Securities [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure		0.0	[4]	0.0
Commercial paper
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents		207.4	[4]	106.6	[5]
Cash and Cash Equivalents, Fair Value Disclosure		207.4	[4]	106.6	[5]
Commercial paper | Level 1
Schedule of Available-for-sale Securities [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure		0.0	[4]	0.0	[5]
Commercial paper | Level 2
Schedule of Available-for-sale Securities [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure		207.4	[4]	106.6	[5]
Commercial paper | Level 3
Schedule of Available-for-sale Securities [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure		0.0	[4]	0.0
Corporate debt securities
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents	[4]	40.2
Cash and Cash Equivalents, Fair Value Disclosure	[4]	40.2
Corporate debt securities | Level 1
Schedule of Available-for-sale Securities [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure	[4]	40.2
Corporate debt securities | Level 2
Schedule of Available-for-sale Securities [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure	[4]	0.0
Corporate debt securities | Level 3
Schedule of Available-for-sale Securities [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure	[4]	0.0
Custody cash deposit
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents		3.2	[4]	2.1	[5]
Cash and Cash Equivalents, Fair Value Disclosure		3.2	[4]	2.1	[5]
Custody cash deposit | Level 1
Schedule of Available-for-sale Securities [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure		3.2	[4]	2.1	[5]
Custody cash deposit | Level 2
Schedule of Available-for-sale Securities [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure		0.0	[4]	0.0	[5]
Custody cash deposit | Level 3
Schedule of Available-for-sale Securities [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure		0.0	[4]	0.0
Money market funds
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents		256.5	[4]	382.4	[5]
Cash and Cash Equivalents, Fair Value Disclosure		256.5	[4]	382.4	[5]
Money market funds | Level 1
Schedule of Available-for-sale Securities [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure		0.0	[4]	0.0	[5]
Money market funds | Level 2
Schedule of Available-for-sale Securities [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure		256.5	[4]	382.4	[5]
Money market funds | Level 3
Schedule of Available-for-sale Securities [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure		0.0	[4]	0.0
Municipal bonds
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents		5.0	[4]	5.0	[5]
Cash and Cash Equivalents, Fair Value Disclosure		5.0	[4]	5.0	[5]
Municipal bonds | Level 1
Schedule of Available-for-sale Securities [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure		5.0	[4]	5.0	[5]
Municipal bonds | Level 2
Schedule of Available-for-sale Securities [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure		0.0	[4]	0.0	[5]
Municipal bonds | Level 3
Schedule of Available-for-sale Securities [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure		0.0	[4]	0.0
Sovereign debt
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents	[4]	15.0
Cash and Cash Equivalents, Fair Value Disclosure	[4]	15.0
Sovereign debt | Level 1
Schedule of Available-for-sale Securities [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure	[4]	0.0
Sovereign debt | Level 2
Schedule of Available-for-sale Securities [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure	[4]	15.0
Sovereign debt | Level 3
Schedule of Available-for-sale Securities [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure	[4]	0.0
U.S. government securities
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents	[4]	309.5		103.0
Cash and Cash Equivalents, Fair Value Disclosure	[4]	309.5		103.0
U.S. government securities | Level 1
Schedule of Available-for-sale Securities [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure	[4]	309.5		103.0
U.S. government securities | Level 2
Schedule of Available-for-sale Securities [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure	[4]	0.0		0.0
U.S. government securities | Level 3
Schedule of Available-for-sale Securities [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure	[4]	$ 0.0		$ 0.0

[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" and included in "Other assets" in the accompanying Consolidated Balance Sheets.

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

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

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