Fair Value of Financial Instruments - Financial Assets and Liabilities Carried at Fair Value (Details) - USD ($) $ in Millions		Jan. 31, 2018	Jan. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total financial assets, Fair Value		$ 347.7	$ 108.1
Total financial liabilities, Fair Value		28.3	8.9
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]	22.5	36.4
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]	320.5	57.8
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]	3.6	3.6
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]		0.4
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]	0.1	9.6
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]	1.0	0.3
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]	1.9	5.4
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]		0.3
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]	4.8	0.6
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]	20.2	0.4
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]	1.4	2.2
Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total financial assets, Fair Value		343.0	94.2
Total financial liabilities, Fair Value		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]	22.5	36.4
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]	320.5	57.8
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
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
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
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
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
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
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
Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total financial assets, Fair Value		4.7	13.9
Total financial liabilities, Fair Value		28.3	8.9
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
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
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]	3.6	3.6
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]		0.4
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]	0.1	9.6
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]	1.0	0.3
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]	1.9	5.4
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]		0.3
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]	4.8	0.6
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]	20.2	0.4
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]	1.4	2.2
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
Total financial liabilities, Fair Value		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
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
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
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
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
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
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
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
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

[1] Included within Other assets, net.

[2] Included within Short-term investments.

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

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