Financial Instruments - Summary of Financial Assets and Liabilities by Categories (Detail) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Financial assets
Cash and cash equivalents	$ 186	$ 157	$ 326
Short-term investments	48	43
Accounts receivable arising from sales of metal concentrates	110	77
Investments in securities	178	114
Derivative assets designated as hedging instruments	2
Derivative assets not designated as hedging instruments	1	7
Other current and non-current financial assets	33	39
Total financial assets	558	437
Financial liabilities
Debt	(2,483)	(2,510)
Deferred payment obligation	(182)
Accounts payable and accrued liabilities	(547)	(478)
Derivative liabilities designated as hedging instruments	(2)	(22)
Other current and non-current financial liabilities	(257)	(259)
Total financial liabilities	(3,471)	(3,269)
Financial Assets, Loans and Receivables [member]
Financial assets
Short-term investments	48	43
Other current and non-current financial assets	33	39
Total financial assets	81	82
Financial Assets, Available-for-Sale [member]
Financial assets
Investments in securities	178	114
Total financial assets	178	114
Financial Assets, Fair Value Through Profit or Loss [member]
Financial assets
Cash and cash equivalents	186	157
Accounts receivable arising from sales of metal concentrates	110	77
Derivative assets not designated as hedging instruments	1	7
Total financial assets	297	241
Effective Hedging Instrument [member]
Financial assets
Derivative assets designated as hedging instruments	2
Total financial assets	2
Financial Liabilities, Fair Value Through Profit or Loss [member]
Financial liabilities
Derivative liabilities designated as hedging instruments	(2)	(22)
Total financial liabilities	(2)	(22)
Financial Liabilities, Held to Maturity/Other Financial Liabilities [member]
Financial liabilities
Debt	(2,483)	(2,510)
Deferred payment obligation	(182)
Accounts payable and accrued liabilities	(547)	(478)
Other current and non-current financial liabilities	(257)	(259)
Total financial liabilities	$ (3,469)	$ (3,247)

Accounts receivable arising from sales of metal concentrates.

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Deferred payment obligation.

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Derivative financial assets designated as hedges.

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Derivative financial assets not designated as hedges.

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Other current and non current financial assets.

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Other current and noncurrent financial liabilities.

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The amount of outstanding funds that the entity is obligated to repay.

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The amount of cash on hand and demand deposits, along with short-term, highly liquid investments that are readily convertible to known amounts of cash and that are subject to an insignificant risk of changes in value. [Refer: Cash; Cash equivalents]

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The amount of assets that are: (a) cash; (b) an equity instrument of another entity; (c) a contractual right: (i) to receive cash or another financial asset from another entity; or (ii) to exchange financial assets or financial liabilities with another entity under conditions that are potentially favourable to the entity; or (d) a contract that will, or may be, settled in the entity’s own equity instruments and is: (i) a non-derivative for which the entity is, or may be, obliged to receive a variable number of the entity’s own equity instruments; or (ii) a derivative that will, or may be, settled other than by the exchange of a fixed amount of cash or another financial asset for a fixed number of the entity’s own equity instruments. For this purpose the entity’s own equity instruments do not include puttable financial instruments classified as equity instruments in accordance with paragraphs 16A-16B of IAS 32, instruments that impose on the entity an obligation to deliver to another party a pro rata share of the net assets of the entity only on liquidation and are classified as equity instruments in accordance with paragraphs 16C-16D of IAS 32, or instruments that are contracts for the future receipt or delivery of the entity’s own equity instruments. [Refer: Financial instruments, class [member]; Financial liabilities]

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The fair value of financial instruments designated as hedging instruments. Hedging instruments are designated derivatives or (for a hedge of the risk of changes in foreign currency exchange rates only) designated non-derivative financial assets or non-derivative financial liabilities whose fair value or cash flows are expected to offset changes in the fair value or cash flows of a designated hedged item. [Refer: At fair value [member]; Derivatives [member]; Derivative financial assets; Derivative financial liabilities; Financial instruments, class [member]; Financial assets; Financial liabilities]

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The amount of non-current financial assets available-for-sale. [Refer: Financial assets available-for-sale; Non-current financial assets]

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