Hedging Instruments - Information on Location and Amounts of Derivative Gains and Losses in Consolidated Financial Statements (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Oct. 31, 2018	Oct. 31, 2017	Oct. 31, 2018	Oct. 31, 2017
Derivative Instruments, Gain (Loss) [Line Items]
Pre-Tax Gain (Loss) Recognized in OCI (Effective Portion)		$ 5.7	$ 9.5	$ 2.8	$ (5.7)
Cash Flow Hedging [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Pre-Tax Gain (Loss) Recognized in OCI (Effective Portion)		5.7	9.5	2.8	(5.7)
Pre-Tax Gain (Loss) Reclassified from Accumulated OCI into Earnings (Effective Portion)		3.4	6.8	10.8	(5.7)
Cash Flow Hedging [Member] | Foreign exchange forward contracts [Member] | Cost of sales [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Pre-Tax Gain (Loss) Recognized in OCI (Effective Portion)	[1]	4.3	4.3	10.6	0.5
Pre-Tax Gain (Loss) Reclassified from Accumulated OCI into Earnings (Effective Portion)	[1]	(0.1)	1.5	2.2	(2.2)
Cash Flow Hedging [Member] | Precious metal collars [Member] | Cost of sales [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Pre-Tax Gain (Loss) Recognized in OCI (Effective Portion)	[1]	0.0	0.3	0.0	0.3
Pre-Tax Gain (Loss) Reclassified from Accumulated OCI into Earnings (Effective Portion)	[1]	0.2	0.1	0.4	0.2
Cash Flow Hedging [Member] | Precious metal forward contracts [Member] | Cost of sales [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Pre-Tax Gain (Loss) Recognized in OCI (Effective Portion)	[1]	(1.4)	(0.1)	(13.5)	(2.7)
Pre-Tax Gain (Loss) Reclassified from Accumulated OCI into Earnings (Effective Portion)	[1]	(0.6)	(0.1)	(0.1)	(1.3)
Cash Flow Hedging [Member] | Cross-currency swaps [Member] | Other (income) expense [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Pre-Tax Gain (Loss) Recognized in OCI (Effective Portion)	[2]	2.8	5.0	5.7	(3.8)
Pre-Tax Gain (Loss) Reclassified from Accumulated OCI into Earnings (Effective Portion)	[2]	4.2	5.7	9.3	(1.3)
Cash Flow Hedging [Member] | Interest Rate Swap [Member] | Interest expense and financing costs [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Pre-Tax Gain (Loss) Recognized in OCI (Effective Portion)	[3]	0.0	0.0	0.0	0.0
Pre-Tax Gain (Loss) Reclassified from Accumulated OCI into Earnings (Effective Portion)	[3]	$ (0.3)	$ (0.4)	$ (1.0)	$ (1.1)

[1] The gain or loss recognized in earnings is included within Cost of sales.

[2] The gain or loss recognized in earnings is included within Other expense, net.

[3] The gain or loss recognized in earnings is included within Interest expense and financing costs.