Financial Instruments - Cost and Fair Value of Financial Instruments (Details) - USD ($) $ in Millions	Oct. 31, 2021	Jan. 31, 2021
Cash equivalents
Amortized Cost	$ 1,748.9	$ 1,772.2
Short-term trading securities
Derivative contract assets, Amortized Cost	0.1	0.1
Derivative contract assets, Gross unrealized gains	0.4	0.4
Derivative contract assets, Gross unrealized losses	(0.3)	(0.3)
Derivative contract assets	0.2	0.2
Amortized Cost	1,191.9	796.3
Gross unrealized gains	57.6	26.7
Gross unrealized losses	(8.2)	(18.2)
Fair Value	1,241.3	804.8
Foreign exchange contracts
Short-term trading securities
Derivative contract assets, Amortized Cost	0.6	0.4
Derivative contract assets, Gross unrealized gains	26.2	9.8
Derivative contract assets, Gross unrealized losses	(0.1)	(0.4)
Derivative contract assets	26.7	9.8
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	(7.8)	(17.5)
Derivative contract liabilities	(7.8)	(17.5)
Level 1
Short-term trading securities
Derivative contract assets	0.0	0.0
Fair Value	1,121.4	771.9
Level 1 | Foreign exchange contracts
Short-term trading securities
Derivative contract assets	0.0	0.0
Derivative contract liabilities	0.0	0.0
Level 2
Short-term trading securities
Derivative contract assets	0.0	0.0
Fair Value	119.7	32.7
Level 2 | Foreign exchange contracts
Short-term trading securities
Derivative contract assets	26.7	9.8
Derivative contract liabilities	(7.8)	(17.5)
Level 3
Short-term trading securities
Derivative contract assets	0.2	0.2
Fair Value	0.2	0.2
Level 3 | Foreign exchange contracts
Short-term trading securities
Derivative contract assets	0.0	0.0
Derivative contract liabilities	0.0	0.0
Money market funds
Cash equivalents
Amortized Cost	1,016.8	686.9
Fair Value	1,016.8	686.9
Money market funds | Level 1
Cash equivalents
Fair Value	1,016.8	686.9
Money market funds | Level 2
Cash equivalents
Fair Value	0.0	0.0
Money market funds | Level 3
Cash equivalents
Fair Value	0.0	0.0
U.S. government securities
Cash equivalents
Amortized Cost	20.0
Fair Value	20.0
U.S. government securities | Level 1
Cash equivalents
Fair Value	0.0
U.S. government securities | Level 2
Cash equivalents
Fair Value	20.0
U.S. government securities | Level 3
Cash equivalents
Fair Value	0.0
Commercial paper
Cash equivalents
Amortized Cost	18.2	36.0
Fair Value	18.2	36.0
Commercial paper | Short-term
Marketable securities:
Amortized Cost	28.0
Gross Unrealized Gains	0.0
Gross Unrealized Losses	0.0
Fair Value	28.0
Commercial paper | Level 1
Cash equivalents
Fair Value	0.0	0.0
Commercial paper | Level 1 | Short-term
Marketable securities:
Fair Value	0.0
Commercial paper | Level 2
Cash equivalents
Fair Value	18.2	36.0
Commercial paper | Level 2 | Short-term
Marketable securities:
Fair Value	28.0
Commercial paper | Level 3
Cash equivalents
Fair Value	0.0	0.0
Commercial paper | Level 3 | Short-term
Marketable securities:
Fair Value	0.0
Municipal bonds
Cash equivalents
Amortized Cost	5.0
Fair Value	5.0
Municipal bonds | Level 1
Cash equivalents
Fair Value	0.0
Municipal bonds | Level 2
Cash equivalents
Fair Value	5.0
Municipal bonds | Level 3
Cash equivalents
Fair Value	0.0
Other
Cash equivalents
Amortized Cost	3.0	4.4
Fair Value	3.0	4.4
Other | Level 1
Cash equivalents
Fair Value	1.9	4.0
Other | Level 2
Cash equivalents
Fair Value	1.1	0.4
Other | Level 3
Cash equivalents
Fair Value	0.0	0.0
Corporate debt securities | Short-term
Marketable securities:
Amortized Cost	8.8
Gross Unrealized Gains	0.0
Gross Unrealized Losses	0.0
Fair Value	8.8
Corporate debt securities | Long-term
Marketable securities:
Amortized Cost	19.7
Gross Unrealized Gains	0.0
Gross Unrealized Losses	0.0
Fair Value	19.7
Corporate debt securities | Level 1 | Short-term
Marketable securities:
Fair Value	0.0
Corporate debt securities | Level 1 | Long-term
Marketable securities:
Fair Value	0.0
Corporate debt securities | Level 2 | Short-term
Marketable securities:
Fair Value	8.8
Corporate debt securities | Level 2 | Long-term
Marketable securities:
Fair Value	19.7
Corporate debt securities | Level 3 | Short-term
Marketable securities:
Fair Value	0.0
Corporate debt securities | Level 3 | Long-term
Marketable securities:
Fair Value	0.0
Common stock | Short-term
Marketable securities:
Amortized Cost	0.0
Gross Unrealized Gains	6.4
Gross Unrealized Losses	0.0
Fair Value	6.4
Common stock | Level 1 | Short-term
Marketable securities:
Fair Value	6.4
Common stock | Level 2 | Short-term
Marketable securities:
Fair Value	0.0
Common stock | Level 3 | Short-term
Marketable securities:
Fair Value	0.0
Other
Marketable securities:
Amortized Cost		4.0
Gross Unrealized Gains		0.0
Gross Unrealized Losses		0.0
Fair Value		4.0
Other | Level 1
Marketable securities:
Fair Value		0.0
Other | Level 2
Marketable securities:
Fair Value		4.0
Other | Level 3
Marketable securities:
Fair Value		0.0
Mutual funds
Short-term trading securities
Amortized Cost	71.7	64.5
Gross Unrealized Gains	24.6	16.5
Gross Unrealized Losses	0.0	0.0
Fair Value	96.3	81.0
Mutual funds | Level 1
Short-term trading securities
Fair Value	96.3	81.0
Mutual funds | Level 2
Short-term trading securities
Fair Value	0.0	0.0
Mutual funds | Level 3
Short-term trading securities
Fair Value	$ 0.0	$ 0.0