Employee Benefit Plans - Reconciliation of Benefit Obligations, Plan Assets and Funded Status (Details) - USD ($) $ in Millions	12 Months Ended
	Jan. 31, 2019	Jan. 31, 2018	Jan. 31, 2017
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at beginning of year	$ 578.1
Fair value of plan assets at end of year	549.7	$ 578.1
Pension Benefits
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Projected benefit obligation at beginning of year	795.6	783.7
Service cost	17.9	17.3	$ 17.4
Interest cost	30.7	32.0	31.6
Participants' contributions	0.0	0.0
MMA retiree drug subsidy	0.0	0.0
Actuarial (gain) loss	(22.4)	21.1
Benefits paid	(26.8)	(59.4)
Translation	0.0	0.9
Projected benefit obligation at end of year	795.0	795.6	783.7
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at beginning of year	578.1	530.1
Actual return on plan assets	(20.1)	86.1
Employer contribution	18.5	21.3
Participants' contributions	0.0	0.0
MMA retiree drug subsidy	0.0	0.0
Benefits paid	(26.8)	(59.4)
Fair value of plan assets at end of year	549.7	578.1	530.1
Funded status at end of year	(245.3)	(217.5)
Other Postretirement Benefits
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Projected benefit obligation at beginning of year	78.5	72.5
Service cost	3.0	2.8	2.8
Interest cost	3.0	3.0	3.1
Participants' contributions	1.3	1.0
MMA retiree drug subsidy	0.1	0.2
Actuarial (gain) loss	(7.0)	1.5
Benefits paid	(2.8)	(2.5)
Translation	0.0	0.0
Projected benefit obligation at end of year	76.1	78.5	72.5
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at beginning of year	0.0	0.0
Actual return on plan assets	0.0	0.0
Employer contribution	1.4	1.3
Participants' contributions	1.3	1.0
MMA retiree drug subsidy	0.1	0.2
Benefits paid	(2.8)	(2.5)
Fair value of plan assets at end of year	0.0	0.0	$ 0.0
Funded status at end of year	$ (76.1)	$ (78.5)