Employee Benefit Plans - Fair Value of Plan Assets (Details) - USD ($) $ in Millions	Jan. 31, 2020	Jan. 31, 2019
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 668.7	$ 549.7
Net assets in fair value hierarchy	489.3	360.3
Investments at NAV practical expedient	179.4	189.4
Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	336.1	236.4
Net assets in fair value hierarchy	336.1	236.4
Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	153.2	123.9
Net assets in fair value hierarchy	153.2	123.9
Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Net assets in fair value hierarchy	0.0	0.0
Equity Securities, Investment Summary | U.S. equity securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	53.0	63.4
Equity Securities, Investment Summary | U.S. equity securities | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	53.0	63.4
Equity Securities, Investment Summary | U.S. equity securities | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Equity Securities, Investment Summary | U.S. equity securities | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Equity Securities, Investment Summary | Mutual funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	119.5	38.7
Equity Securities, Investment Summary | Mutual funds | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	119.5	38.7
Equity Securities, Investment Summary | Mutual funds | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Equity Securities, Investment Summary | Mutual funds | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Fixed Income Securities | Government bonds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	100.5	80.8
Fixed Income Securities | Government bonds | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	99.3	79.6
Fixed Income Securities | Government bonds | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1.2	1.2
Fixed Income Securities | Government bonds | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Fixed Income Securities | Corporate bonds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	139.9	122.7
Fixed Income Securities | Corporate bonds | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Fixed Income Securities | Corporate bonds | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	139.9	122.7
Fixed Income Securities | Corporate bonds | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Other Investments | Mutual funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	73.9	52.0
Other Investments | Mutual funds | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	61.8	52.0
Other Investments | Mutual funds | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	12.1	0.0
Other Investments | Mutual funds | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Other Investments | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	2.5	2.7
Other Investments | Cash and cash equivalents | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	2.5	2.7
Other Investments | Cash and cash equivalents | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Other Investments | Cash and cash equivalents | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 0.0	$ 0.0