Employee Benefit Plans - Components of Net Periodic Benefit Cost and Other Amounts Recognized in Other Comprehensive Earnings (Details) - USD ($) $ in Millions		12 Months Ended
		Jan. 31, 2018	Jan. 31, 2017	Jan. 31, 2016
Defined Benefit Plan Disclosure [Line Items]
Net actuarial (gain) loss		$ (30.6)	$ (14.1)	$ (122.5)
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss), Reclassification Adjustment from AOCI, before Tax	[1]	(13.3)	(14.7)	(30.4)
Recognized Prior Service (Cost) Credit	[1]	(0.5)	(0.7)	(0.6)
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost		17.3	17.4	22.6
Interest cost		32.0	31.6	30.6
Expected return on plan assets		(32.9)	(23.5)	(24.7)
Curtailments		0.0	0.0	0.2
Amortization of prior service cost		0.2	0.0	0.0
Amortization of net loss		13.2	14.7	28.9
Net periodic benefit cost		29.8	40.2	57.6
Net actuarial (gain) loss		(32.1)	(3.6)	(102.1)
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss), Reclassification Adjustment from AOCI, before Tax		(13.2)	(14.7)	(28.9)
Recognized Prior Service (Cost) Credit		(0.2)	0.0	(0.1)
Total recognized in other comprehensive earnings		(45.5)	(18.3)	(131.1)
Total Recognized In Net Periodic Benefit Cost And Other Comprehensive Earnings		(15.7)	21.9	(73.5)
Other Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost		2.8	2.8	4.2
Interest cost		3.0	3.1	3.2
Expected return on plan assets		0.0	0.0	0.0
Curtailments		0.0	0.0	0.0
Amortization of prior service cost		(0.7)	(0.7)	(0.7)
Amortization of net loss		0.1	0.0	1.5
Net periodic benefit cost		5.2	5.2	8.2
Net actuarial (gain) loss		1.5	(10.5)	(20.4)
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss), Reclassification Adjustment from AOCI, before Tax		(0.1)	0.0	(1.5)
Recognized Prior Service (Cost) Credit		0.7	0.7	0.7
Total recognized in other comprehensive earnings		2.1	(9.8)	(21.2)
Total Recognized In Net Periodic Benefit Cost And Other Comprehensive Earnings		$ 7.3	$ (4.6)	$ (13.0)

[1] These losses (gains) are included in the computation of net periodic pension costs (see "Note N. Employee Benefit Plans" for additional details).