Hedging Instruments - Information on Location and Amounts of Derivative Gains and Losses in Consolidated Financial Statements (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jul. 31, 2020	Jul. 31, 2019	Jul. 31, 2020		Jul. 31, 2019
Derivative Instruments, Gain (Loss) [Line Items]
Cost of sales	$ 285.5	$ 390.8	$ 532.0		$ 774.7
Interest expense and financing costs	11.1	9.8	20.9		20.2
Other income, net	(0.8)	(0.9)	(26.2)		(1.9)
Other comprehensive income (loss), net of tax	59.5	7.0	41.0		(6.2)
Precious metal forward contracts
Derivative Instruments, Gain (Loss) [Line Items]
Reclassified deferred hedging gains resulting from discontinuance of cash flow hedge			4.2
Cash Flow Hedging | Foreign exchange forward contracts | Cost of sales
Derivative Instruments, Gain (Loss) [Line Items]
Pre-tax gain/loss recognized in OCI	0.0	0.0	0.0		0.0
Pre-tax gain/loss reclassified from accumulated OCI into earnings	(0.7)	(1.4)	(1.1)		(2.5)
Cash Flow Hedging | Foreign exchange forward contracts | Interest expense and financing costs
Derivative Instruments, Gain (Loss) [Line Items]
Pre-tax gain/loss recognized in OCI	0.0	0.0	0.0		0.0
Pre-tax gain/loss reclassified from accumulated OCI into earnings	0.0	0.0	0.0		0.0
Cash Flow Hedging | Foreign exchange forward contracts | Other income, net
Derivative Instruments, Gain (Loss) [Line Items]
Pre-tax gain/loss recognized in OCI	0.0	0.0	0.0		0.0
Pre-tax gain/loss reclassified from accumulated OCI into earnings	0.0	0.0	0.0		0.0
Cash Flow Hedging | Foreign exchange forward contracts | Other comprehensive loss, net of tax
Derivative Instruments, Gain (Loss) [Line Items]
Pre-tax gain/loss recognized in OCI	(3.2)	(2.6)	(4.3)		3.1
Pre-tax gain/loss reclassified from accumulated OCI into earnings	0.7	1.4	1.1		2.5
Cash Flow Hedging | Precious metal collars | Cost of sales
Derivative Instruments, Gain (Loss) [Line Items]
Pre-tax gain/loss reclassified from accumulated OCI into earnings		(0.1)			(0.2)
Cash Flow Hedging | Precious metal collars | Interest expense and financing costs
Derivative Instruments, Gain (Loss) [Line Items]
Pre-tax gain/loss reclassified from accumulated OCI into earnings		0.0			0.0
Cash Flow Hedging | Precious metal collars | Other income, net
Derivative Instruments, Gain (Loss) [Line Items]
Pre-tax gain/loss reclassified from accumulated OCI into earnings		0.0			0.0
Cash Flow Hedging | Precious metal collars | Other comprehensive loss, net of tax
Derivative Instruments, Gain (Loss) [Line Items]
Pre-tax gain/loss reclassified from accumulated OCI into earnings		0.1			0.2
Cash Flow Hedging | Precious metal forward contracts | Cost of sales
Derivative Instruments, Gain (Loss) [Line Items]
Pre-tax gain/loss recognized in OCI	0.0	0.0	0.0		0.0
Pre-tax gain/loss reclassified from accumulated OCI into earnings	(0.9)	1.1	(5.5)	[1]	2.2
Cash Flow Hedging | Precious metal forward contracts | Interest expense and financing costs
Derivative Instruments, Gain (Loss) [Line Items]
Pre-tax gain/loss recognized in OCI	0.0	0.0	0.0		0.0
Pre-tax gain/loss reclassified from accumulated OCI into earnings	0.0	0.0	0.0	[1]	0.0
Cash Flow Hedging | Precious metal forward contracts | Other income, net
Derivative Instruments, Gain (Loss) [Line Items]
Pre-tax gain/loss recognized in OCI	0.0	0.0	0.0		0.0
Pre-tax gain/loss reclassified from accumulated OCI into earnings	0.0	0.0	0.0	[1]	0.0
Cash Flow Hedging | Precious metal forward contracts | Other comprehensive loss, net of tax
Derivative Instruments, Gain (Loss) [Line Items]
Pre-tax gain/loss recognized in OCI	9.1	8.0	9.7		6.6
Pre-tax gain/loss reclassified from accumulated OCI into earnings	0.9	(1.1)	5.5	[1]	(2.2)
Cash Flow Hedging | Cross-currency swaps | Cost of sales
Derivative Instruments, Gain (Loss) [Line Items]
Pre-tax gain/loss recognized in OCI	0.0	0.0	0.0		0.0
Pre-tax gain/loss reclassified from accumulated OCI into earnings	0.0	0.0	0.0		0.0
Cash Flow Hedging | Cross-currency swaps | Interest expense and financing costs
Derivative Instruments, Gain (Loss) [Line Items]
Pre-tax gain/loss recognized in OCI	0.0	0.0	0.0		0.0
Pre-tax gain/loss reclassified from accumulated OCI into earnings	(1.5)	0.0	(3.1)		0.0
Cash Flow Hedging | Cross-currency swaps | Other income, net
Derivative Instruments, Gain (Loss) [Line Items]
Pre-tax gain/loss recognized in OCI	0.0	0.0	0.0		0.0
Pre-tax gain/loss reclassified from accumulated OCI into earnings	6.4	5.5	11.2		(2.3)
Cash Flow Hedging | Cross-currency swaps | Other comprehensive loss, net of tax
Derivative Instruments, Gain (Loss) [Line Items]
Pre-tax gain/loss recognized in OCI	(1.1)	(0.9)	7.7		12.5
Pre-tax gain/loss reclassified from accumulated OCI into earnings	(4.9)	(5.5)	(8.1)		2.3
Cash Flow Hedging | Forward-starting interest rate swaps | Cost of sales
Derivative Instruments, Gain (Loss) [Line Items]
Pre-tax gain/loss reclassified from accumulated OCI into earnings	0.0	0.0	0.0		0.0
Cash Flow Hedging | Forward-starting interest rate swaps | Interest expense and financing costs
Derivative Instruments, Gain (Loss) [Line Items]
Pre-tax gain/loss reclassified from accumulated OCI into earnings	0.3	0.3	0.7		0.6
Cash Flow Hedging | Forward-starting interest rate swaps | Other income, net
Derivative Instruments, Gain (Loss) [Line Items]
Pre-tax gain/loss reclassified from accumulated OCI into earnings	0.0	0.0	0.0		0.0
Cash Flow Hedging | Forward-starting interest rate swaps | Other comprehensive loss, net of tax
Derivative Instruments, Gain (Loss) [Line Items]
Pre-tax gain/loss reclassified from accumulated OCI into earnings	$ (0.3)	$ (0.3)	$ (0.7)		$ (0.6)

[1] Includes net gains of $4.2 million in the six months ended July 31, 2020 reclassified from Accumulated OCI into Cost of sales on the Condensed Consolidated Statement of Earnings as a result of the discontinuation of hedge accounting on certain precious metal forward contracts.