Fair Value of Financial Instruments - Financial Assets and Liabilities Carried at Fair Value (Details) - USD ($) $ in Millions		Apr. 30, 2018	Jan. 31, 2018	Apr. 30, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total financial assets, Fair Value		$ 253.9	$ 347.7	$ 170.9
Total financial liabilities, Fair Value		31.8	28.3	16.1
Other assets, net [Member] | Marketable securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Assets, Fair Value	[1]	37.1	22.5	36.9
Short-term Investments [Member] | Bank Time Deposits [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Assets, Fair Value	[2]	212.7	320.5	121.2
Prepaid expenses and other current assets [Member] | Cash Flow Hedging [Member] | Precious Metal Forward Contracts [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets, Fair Value	[3]	1.8	3.6	3.9
Prepaid expenses and other current assets [Member] | Cash Flow Hedging [Member] | Precious metal collars [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets, Fair Value	[3]			0.5
Prepaid expenses and other current assets [Member] | Cash Flow Hedging [Member] | Foreign Exchange Forward [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets, Fair Value	[3]	0.9	0.1	6.6
Prepaid expenses and other current assets [Member] | Not Designated as Hedging Instrument [Member] | Foreign Exchange Forward [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets, Fair Value	[3]	1.4	1.0	1.8
Accounts Payable and Accrued Liabilities [Member] | Cash Flow Hedging [Member] | Precious Metal Forward Contracts [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liability, Fair Value	[4]	5.0	1.9	5.7
Accounts Payable and Accrued Liabilities [Member] | Cash Flow Hedging [Member] | Precious metal collars [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liability, Fair Value	[4]			0.4
Accounts Payable and Accrued Liabilities [Member] | Cash Flow Hedging [Member] | Foreign Exchange Forward [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liability, Fair Value	[4]	2.4	4.8	1.7
Accounts Payable and Accrued Liabilities [Member] | Cash Flow Hedging [Member] | Currency Swap [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liability, Fair Value	[4]	23.6	20.2	7.9
Accounts Payable and Accrued Liabilities [Member] | Not Designated as Hedging Instrument [Member] | Foreign Exchange Forward [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liability, Fair Value	[4]	0.8	1.4	0.4
Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total financial assets, Fair Value		249.8	343.0	158.1
Total financial liabilities, Fair Value		0.0	0.0	0.0
Level 1 [Member] | Other assets, net [Member] | Marketable securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Assets, Fair Value	[1]	37.1	22.5	36.9
Level 1 [Member] | Short-term Investments [Member] | Bank Time Deposits [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Assets, Fair Value	[2]	212.7	320.5	121.2
Level 1 [Member] | Prepaid expenses and other current assets [Member] | Cash Flow Hedging [Member] | Precious Metal Forward Contracts [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets, Fair Value	[3]	0.0	0.0	0.0
Level 1 [Member] | Prepaid expenses and other current assets [Member] | Cash Flow Hedging [Member] | Precious metal collars [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets, Fair Value	[3]			0.0
Level 1 [Member] | Prepaid expenses and other current assets [Member] | Cash Flow Hedging [Member] | Foreign Exchange Forward [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets, Fair Value	[3]	0.0	0.0	0.0
Level 1 [Member] | Prepaid expenses and other current assets [Member] | Not Designated as Hedging Instrument [Member] | Foreign Exchange Forward [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets, Fair Value	[3]	0.0	0.0	0.0
Level 1 [Member] | Accounts Payable and Accrued Liabilities [Member] | Cash Flow Hedging [Member] | Precious Metal Forward Contracts [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liability, Fair Value	[4]	0.0	0.0	0.0
Level 1 [Member] | Accounts Payable and Accrued Liabilities [Member] | Cash Flow Hedging [Member] | Precious metal collars [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liability, Fair Value	[4]			0.0
Level 1 [Member] | Accounts Payable and Accrued Liabilities [Member] | Cash Flow Hedging [Member] | Foreign Exchange Forward [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liability, Fair Value	[4]	0.0	0.0	0.0
Level 1 [Member] | Accounts Payable and Accrued Liabilities [Member] | Cash Flow Hedging [Member] | Currency Swap [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liability, Fair Value	[4]	0.0	0.0	0.0
Level 1 [Member] | Accounts Payable and Accrued Liabilities [Member] | Not Designated as Hedging Instrument [Member] | Foreign Exchange Forward [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liability, Fair Value	[4]	0.0	0.0	0.0
Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total financial assets, Fair Value		4.1	4.7	12.8
Total financial liabilities, Fair Value		31.8	28.3	16.1
Level 2 [Member] | Other assets, net [Member] | Marketable securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Assets, Fair Value	[1]	0.0	0.0	0.0
Level 2 [Member] | Short-term Investments [Member] | Bank Time Deposits [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Assets, Fair Value	[2]	0.0	0.0	0.0
Level 2 [Member] | Prepaid expenses and other current assets [Member] | Cash Flow Hedging [Member] | Precious Metal Forward Contracts [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets, Fair Value	[3]	1.8	3.6	3.9
Level 2 [Member] | Prepaid expenses and other current assets [Member] | Cash Flow Hedging [Member] | Precious metal collars [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets, Fair Value	[3]			0.5
Level 2 [Member] | Prepaid expenses and other current assets [Member] | Cash Flow Hedging [Member] | Foreign Exchange Forward [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets, Fair Value	[3]	0.9	0.1	6.6
Level 2 [Member] | Prepaid expenses and other current assets [Member] | Not Designated as Hedging Instrument [Member] | Foreign Exchange Forward [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets, Fair Value	[3]	1.4	1.0	1.8
Level 2 [Member] | Accounts Payable and Accrued Liabilities [Member] | Cash Flow Hedging [Member] | Precious Metal Forward Contracts [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liability, Fair Value	[4]	5.0	1.9	5.7
Level 2 [Member] | Accounts Payable and Accrued Liabilities [Member] | Cash Flow Hedging [Member] | Precious metal collars [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liability, Fair Value	[4]			0.4
Level 2 [Member] | Accounts Payable and Accrued Liabilities [Member] | Cash Flow Hedging [Member] | Foreign Exchange Forward [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liability, Fair Value	[4]	2.4	4.8	1.7
Level 2 [Member] | Accounts Payable and Accrued Liabilities [Member] | Cash Flow Hedging [Member] | Currency Swap [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liability, Fair Value	[4]	23.6	20.2	7.9
Level 2 [Member] | Accounts Payable and Accrued Liabilities [Member] | Not Designated as Hedging Instrument [Member] | Foreign Exchange Forward [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liability, Fair Value	[4]	0.8	1.4	0.4
Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total financial assets, Fair Value		0.0	0.0	0.0
Total financial liabilities, Fair Value		0.0	0.0	0.0
Level 3 [Member] | Other assets, net [Member] | Marketable securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Assets, Fair Value	[1]	0.0	0.0	0.0
Level 3 [Member] | Short-term Investments [Member] | Bank Time Deposits [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Assets, Fair Value	[2]	0.0	0.0	0.0
Level 3 [Member] | Prepaid expenses and other current assets [Member] | Cash Flow Hedging [Member] | Precious Metal Forward Contracts [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets, Fair Value	[3]	0.0	0.0	0.0
Level 3 [Member] | Prepaid expenses and other current assets [Member] | Cash Flow Hedging [Member] | Precious metal collars [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets, Fair Value	[3]			0.0
Level 3 [Member] | Prepaid expenses and other current assets [Member] | Cash Flow Hedging [Member] | Foreign Exchange Forward [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets, Fair Value	[3]	0.0	0.0	0.0
Level 3 [Member] | Prepaid expenses and other current assets [Member] | Not Designated as Hedging Instrument [Member] | Foreign Exchange Forward [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets, Fair Value	[3]	0.0	0.0	0.0
Level 3 [Member] | Accounts Payable and Accrued Liabilities [Member] | Cash Flow Hedging [Member] | Precious Metal Forward Contracts [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liability, Fair Value	[4]	0.0	0.0	0.0
Level 3 [Member] | Accounts Payable and Accrued Liabilities [Member] | Cash Flow Hedging [Member] | Precious metal collars [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liability, Fair Value	[4]			0.0
Level 3 [Member] | Accounts Payable and Accrued Liabilities [Member] | Cash Flow Hedging [Member] | Foreign Exchange Forward [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liability, Fair Value	[4]	0.0	0.0	0.0
Level 3 [Member] | Accounts Payable and Accrued Liabilities [Member] | Cash Flow Hedging [Member] | Currency Swap [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liability, Fair Value	[4]	0.0	0.0	0.0
Level 3 [Member] | Accounts Payable and Accrued Liabilities [Member] | Not Designated as Hedging Instrument [Member] | Foreign Exchange Forward [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liability, Fair Value	[4]	$ 0.0	$ 0.0	$ 0.0

[1] a Included within Other assets, net.

[2] b Included within Short-term investments.

[3] c Included within Prepaid expenses and other current assets or Other assets, net based on the maturity of the contract.

[4] d Included within Accounts payable and accrued liabilities or Other long-term liabilities based on the maturity of the contract.