Net Income Per Share - Computation of Net Income Per Share Amounts (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	12 Months Ended
	Jan. 31, 2022	Jan. 31, 2021	Jan. 31, 2020
Numerator:
Net income	$ 497.0	$ 1,208.2	$ 214.5
Denominator:
Weighted average shares for basic net income per share (in shares)	219.7	219.4	219.7
Effect of dilutive securities (in shares)	2.3	2.7	2.8
Weighted average shares for dilutive net income per share (in shares)	222.0	222.1	222.5
Basic net income per share (in dollars per share)	$ 2.26	$ 5.51	$ 0.98
Diluted net income per share (in dollars per share)	$ 2.24	$ 5.44	$ 0.96