Financial Instruments Cost and Fair Value of Financial Instruments (Details) - USD ($) $ in Millions	Oct. 31, 2017	Jan. 31, 2017	Oct. 31, 2016	Jan. 31, 2016
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents	$ 1,025.2	$ 1,213.1	$ 1,436.5	$ 1,353.0
Derivative contract assets, Amortized Cost	2.4	2.2
Derivative contract assets, Gross unrealized gains	7.2	12.3
Derivative contract assets, Gross unrealized losses	(0.5)	(1.3)
Derivative contract assets	9.1	13.2
Derivative contract liabilities, Amortized Cost	0.0	0.0
Derivative contract liabilities, Gross unrealized gains	0.0	0.0
Derivative contract liabilities, Gross unrealized losses	(8.9)	(10.4)
Derivative contract liabilities	(8.9)	(10.4)
Amortized Cost	1,329.9	1,903.5
Gross unrealized gains	15.5	17.4
Gross unrealized losses	(9.9)	(13.6)
Fair Value	1,335.5	1,907.3
Marketable Securities, Current
Schedule of Available-for-sale Securities [Line Items]
Mutual funds, Amortized Cost	49.1	44.8
Mutual funds, Gross unrealized gains	7.4	2.5
Mutual funds, Gross unrealized losses	0.0	0.0
Mutual funds, Fair Value	56.5	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	30.4	19.6
Marketable securities, Gross unrealized gains	0.0	0.0
Marketable securities, Gross unrealized losses	0.0	0.0
Marketable securities, Fair Value	30.4	19.6
Marketable Securities, Current | Certificates of deposit
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Amortized Cost	4.0	157.3
Marketable securities, Gross unrealized gains	0.0	0.0
Marketable securities, Gross unrealized losses	0.0	0.0
Marketable securities, Fair Value	4.0	157.3
Marketable Securities, Current | Commercial paper
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Amortized Cost	31.3	109.2
Marketable securities, Gross unrealized gains	0.0	0.0
Marketable securities, Gross unrealized losses	0.0	0.0
Marketable securities, Fair Value	31.3	109.2
Marketable Securities, Current | Corporate debt securities
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Amortized Cost	218.7	234.7
Marketable securities, Gross unrealized gains	0.1	0.0
Marketable securities, Gross unrealized losses	(0.1)	(0.2)
Marketable securities, Fair Value	218.7	234.5
Marketable Securities, Current | Municipal bonds
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Amortized Cost	15.5	43.4
Marketable securities, Gross unrealized gains		0.0
Marketable securities, Gross unrealized losses	0.0	0.0
Marketable securities, Fair Value	15.5	43.4
Marketable Securities, Current | Sovereign debt
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Amortized Cost	6.0	30.0
Marketable securities, Gross unrealized gains	0.0	0.0
Marketable securities, Gross unrealized losses	0.0	0.0
Marketable securities, Fair Value	6.0	30.0
Marketable Securities, Current | U.S. government securities
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Amortized Cost	58.8	32.3
Marketable securities, Gross unrealized gains	0.0	0.0
Marketable securities, Gross unrealized losses	0.0	0.0
Marketable securities, Fair Value	58.8	32.3
Marketable Securities, Noncurrent | Agency bonds
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Amortized Cost	12.2	7.1
Marketable securities, Gross unrealized gains	0.0	0.0
Marketable securities, Gross unrealized losses	0.0	0.0
Marketable securities, Fair Value	12.2	7.1
Marketable Securities, Noncurrent | Asset backed securities
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Amortized Cost	60.8	65.8
Marketable securities, Gross unrealized gains	0.0	0.1
Marketable securities, Gross unrealized losses	(0.1)	0.0
Marketable securities, Fair Value	60.7	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	(0.1)	(0.1)
Marketable securities, Fair Value	143.2	172.1
Marketable Securities, Noncurrent | Municipal bonds
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Amortized Cost	12.8	10.7
Marketable securities, Gross unrealized gains	0.0	0.0
Marketable securities, Gross unrealized losses	(0.1)	0.0
Marketable securities, Fair Value	12.7	10.7
Marketable Securities, Noncurrent | Sovereign debt
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Amortized Cost	2.7	1.5
Marketable securities, Gross unrealized gains	0.0	0.0
Marketable securities, Gross unrealized losses	0.0	0.0
Marketable securities, Fair Value	2.7	1.5
Marketable Securities, Noncurrent | U.S. government securities
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Amortized Cost	32.9	48.8
Marketable securities, Gross unrealized gains	0.0	0.1
Marketable securities, Gross unrealized losses	(0.1)	0.0
Marketable securities, Fair Value	32.8	48.9
Other asset
Schedule of Available-for-sale Securities [Line Items]
Convertible debt securities, Amortized Cost		4.9
Convertible debt securities, Gross unrealized gains		2.3
Convertible debt securities, Gross unrealized losses		(1.6)
Convertible debt securities, Fair Value		5.6
Other asset | Convertible debt securities
Schedule of Available-for-sale Securities [Line Items]
Convertible debt securities, Amortized Cost	8.4
Convertible debt securities, Gross unrealized gains	0.6
Convertible debt securities, Gross unrealized losses	0.0
Convertible debt securities, Fair Value	9.0
Agency bonds
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents		6.0
Cash equivalents, Fair Value		6.0
Certificates of deposit
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents	63.1	63.1
Cash equivalents, Fair Value	63.1	63.1
Corporate debt securities
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents	8.0	40.2
Cash equivalents, Fair Value	8.0	40.2
Commercial paper
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents	166.5	207.4
Cash equivalents, Fair Value	166.5	207.4
Custody cash deposit
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents	0.9	3.2
Cash equivalents, Fair Value	0.9	3.2
Municipal bonds
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents		5.0
Cash equivalents, Fair Value		5.0
Money Market funds
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents	144.8	256.5
Cash equivalents, Fair Value	144.8	256.5
Sovereign debt
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents		15.0
Cash equivalents, Fair Value		15.0
U.S. government securities
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents	250.0	309.5
Cash equivalents, Fair Value	250.0	309.5
Level 1
Schedule of Available-for-sale Securities [Line Items]
Derivative contract assets	0.0	0.0
Derivative contract liabilities	0.0	0.0
Fair Value	883.9	1,193.8
Level 1 | Marketable Securities, Current
Schedule of Available-for-sale Securities [Line Items]
Mutual funds, Fair Value	56.5	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	4.0	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	218.7	234.5
Level 1 | Marketable Securities, Current | Municipal bonds
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Fair Value	15.5	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	58.8	32.3
Level 1 | Marketable Securities, Noncurrent | Agency bonds
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Fair Value	12.2	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	143.2	172.1
Level 1 | Marketable Securities, Noncurrent | Municipal bonds
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Fair Value	12.7	10.7
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	32.8	48.9
Level 1 | Other asset
Schedule of Available-for-sale Securities [Line Items]
Convertible debt securities, Fair Value		0.0
Level 1 | Other asset | Convertible debt securities
Schedule of Available-for-sale Securities [Line Items]
Convertible debt securities, Fair Value	0.0
Level 1 | Agency bonds
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents, Fair Value		6.0
Level 1 | Certificates of deposit
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents, Fair Value	63.1	63.1
Level 1 | Corporate debt securities
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents, Fair Value	8.0	40.2
Level 1 | Commercial paper
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents, Fair Value	0.0	0.0
Level 1 | Custody cash deposit
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents, Fair Value	0.9	3.2
Level 1 | Municipal bonds
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents, Fair Value		5.0
Level 1 | Money Market funds
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents, Fair Value	0.0	0.0
Level 1 | Sovereign debt
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents, Fair Value		0.0
Level 1 | U.S. government securities
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents, Fair Value	250.0	309.5
Level 2
Schedule of Available-for-sale Securities [Line Items]
Derivative contract assets	7.1	11.9
Derivative contract liabilities	(8.9)	(10.4)
Fair Value	440.6	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	30.4	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	31.3	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	6.0	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	60.7	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	2.7	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 | Other asset
Schedule of Available-for-sale Securities [Line Items]
Convertible debt securities, Fair Value		0.0
Level 2 | Other asset | Convertible debt securities
Schedule of Available-for-sale Securities [Line Items]
Convertible debt securities, Fair Value	0.0
Level 2 | Agency bonds
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents, Fair Value		0.0
Level 2 | Certificates of deposit
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents, Fair Value	0.0	0.0
Level 2 | Corporate debt securities
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents, Fair Value	0.0	0.0
Level 2 | Commercial paper
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents, Fair Value	166.5	207.4
Level 2 | Custody cash deposit
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents, Fair Value	0.0	0.0
Level 2 | Municipal bonds
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents, Fair Value		0.0
Level 2 | Money Market funds
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents, Fair Value	144.8	256.5
Level 2 | Sovereign debt
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents, Fair Value		15.0
Level 2 | U.S. government securities
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents, Fair Value	0.0	0.0
Level 3
Schedule of Available-for-sale Securities [Line Items]
Derivative contract assets	2.0	1.3
Derivative contract liabilities	0.0	0.0
Fair Value	11.0	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	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 | Other asset
Schedule of Available-for-sale Securities [Line Items]
Convertible debt securities, Fair Value		5.6
Level 3 | Other asset | Convertible debt securities
Schedule of Available-for-sale Securities [Line Items]
Convertible debt securities, Fair Value	9.0
Level 3 | Agency bonds
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents, Fair Value		0.0
Level 3 | Certificates of deposit
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents, Fair Value	0.0	0.0
Level 3 | Corporate debt securities
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents, Fair Value	0.0	0.0
Level 3 | Commercial paper
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents, Fair Value	0.0	0.0
Level 3 | Custody cash deposit
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents, Fair Value	0.0	0.0
Level 3 | Municipal bonds
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents, Fair Value		0.0
Level 3 | Money Market funds
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents, Fair Value	0.0	0.0
Level 3 | Sovereign debt
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents, Fair Value		0.0
Level 3 | U.S. government securities
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents, Fair Value	$ 0.0	$ 0.0