Employee Benefit Plans - Fair Value of Plan Assets (Details) - USD ($) $ in Millions	Jan. 31, 2019	Jan. 31, 2018
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 549.7	$ 578.1
Net assets in fair value hierarchy	360.3	365.1
Investments at NAV practical expedient	189.4	213.0
Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	236.4	248.2
Net assets in fair value hierarchy	236.4	248.2
Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	123.9	116.9
Net assets in fair value hierarchy	123.9	116.9
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	63.4	74.3
Equity Securities, Investment Summary | U.S. equity securities | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	63.4	74.3
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 fund
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	38.7	44.7
Equity Securities, Investment Summary | Mutual fund | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	38.7	44.7
Equity Securities, Investment Summary | Mutual fund | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Equity Securities, Investment Summary | Mutual fund | 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	80.8	79.0
Fixed Income Securities | Government bonds | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	79.6	77.3
Fixed Income Securities | Government bonds | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1.2	1.7
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	122.7	115.2
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	122.7	115.2
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 fund
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	52.0	49.6
Other Investments | Mutual fund | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	52.0	49.6
Other Investments | Mutual fund | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Other Investments | Mutual fund | 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	2.7	2.3
Other Investments | Cash and cash equivalents | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	2.7	2.3
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