SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES: (Policies)	12 Months Ended
Dec. 31, 2012
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES:
Principles of consolidation	The consolidated financial statements include the accounts of subsidiaries of which the Company has voting control, in accordance with Accounting Standards Codification 810 Consolidation. Such financial statements are prepared in accordance with accounting principles generally accepted in the United States (“U.S. GAAP”).
Use of estimates	The preparation of financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, and disclosure of contingent assets and liabilities at the date of the financial statements, and the reported amounts of revenues and expenses during the reporting period. Significant items subject to such estimates and assumptions include the carrying value of ore reserves that are the basis for future cash flow estimates and amortization calculations; environmental, reclamation, closure and retirement obligations; estimates of recoverable copper in mill and leach stockpiles; asset impairments (including estimates of future cash flows); bad debts; inventory obsolescence; deferred and current income tax; valuation allowances for deferred tax assets; reserves for contingencies and litigation; and fair value of financial instruments. Management bases its estimates on the Company’s historical experience and on various other assumptions that are believed to be reasonable under the circumstances. Actual results could differ from those estimates.
Revenue recognition	Substantially all of the Company’s copper is sold under annual or other longer-term contracts. Revenue is recognized when title passes to the customer. The passing of title is based on terms of the contract, generally upon shipment. Copper revenue is determined based on the monthly average of prevailing commodity prices according to the terms of the contracts. The Company provides allowances for doubtful accounts based upon historical bad debt and claims experience and periodic evaluation of specific customer accounts. For certain of the Company’s sales of copper and molybdenum products, customer contracts allow for pricing based on a month subsequent to shipping, in most cases within the following three months and occasionally in some cases a few additional months. In such cases, revenue is recorded at a provisional price at the time of shipment. The provisionally priced copper sales are adjusted to reflect forward LME or COMEX copper prices at the end of each month until a final adjustment is made to the price of the shipments upon settlement with customers pursuant to the terms of the contract. In the case of molybdenum sales, for which there are no published forward prices, the provisionally priced sales are adjusted to reflect the market prices at the end of each month until a final adjustment is made to the price of the shipments upon settlement with customers pursuant to the terms of the contract. These provisional pricing arrangements are accounted for separately from the contract as an embedded derivative instrument under ASC 815-30 “Derivatives and Hedging — Cash Flow Hedges.” The Company sells copper in concentrate, anode, blister and refined form at industry standard commercial terms. Net sales include the invoiced value and corresponding fair value adjustment of the related forward contract of copper, zinc, silver, molybdenum, acid and other metals.
Shipping and handling fees and costs	Amounts billed to customers for shipping and handling are classified as sales. Amounts incurred for shipping and handling are included in cost of sales (exclusive of depreciation, amortization and depletion).
Cash and cash equivalents	Cash and cash equivalents include bank deposits, certificates of deposit and short-term investment funds with original maturities of three months or less at the date of purchase. The carrying value of cash and cash equivalents approximates fair value.
Short-term investments	The Company accounts for short-term investments in accordance with ASC 320-10 “Investments Debt and Equity Securities — Recognition.” The Company determines the appropriate classification of all short-term investments as held-to-maturity, available-for-sale or trading at the time of purchase and re-evaluates such classifications as of each balance sheet date. Unrealized gains and losses on available-for-sale investments, net of taxes, are reported as a component of accumulated other comprehensive income (loss) in stockholders’ equity, unless such loss is deemed to be other than temporary.
Inventories	Metal inventories, consisting of work—in-process and finished goods, are carried at the lower of average cost or market. Costs incurred in the production of metal inventories exclude general and administrative costs. Work-in-process inventories represent materials that are in the process of being converted into a saleable product. Conversion processes vary depending on the nature of the copper ore and the specific mining operation. For sulfide ores, processing includes milling and concentrating and results in the production of copper and molybdenum concentrates. Finished goods include saleable products (e.g., copper concentrates, copper anodes, copper cathodes, copper rod, molybdenum concentrate and other metallurgical products). Supplies inventories are carried at the lower of average cost less a reserve for obsolescence or market.
Long-term inventory - Leachable material	The leaching process is an integral part of the mining operations carried out at the Company’s open-pit mines. The Company capitalizes the production cost of leachable material at its Toquepala, La Caridad and Buenavista mines recognizing it as inventory. The estimates of recoverable mineral content contained in the leaching dumps are supported by engineering studies. As the production cycle of the leaching process is significantly longer than the conventional process of concentrating, smelting and electrolytic refining, the Company includes on its balance sheet, current leach inventory (included in work-in-process inventories) and long-term leach inventory. The cost attributed to the leach material is charged to cost of sales generally over a five-year period (the average estimated recovery period based on the historical recovery percentages of each mine).
Property	Property is recorded at acquisition cost, net of accumulated depreciation and amortization. Cost includes major expenditures for improvements and replacements, which extend useful lives or increase capacity and interest costs associated with significant capital additions. Maintenance, repairs, normal development costs at existing mines, and gains or losses on assets retired or sold are reflected in earnings as incurred. Buildings and equipment are depreciated on the straight-line method over estimated lives from five to 40 years or the estimated life of the mine if shorter.
Mine development	Mine development includes primarily the cost of acquiring land rights to an exploitable ore body, pre-production stripping costs at new mines that are commercially exploitable, costs associated with bringing new mineral properties into production, and removal of overburden to prepare unique and identifiable areas outside the current mining area for such future production. Mine development costs are amortized on a unit of production basis over the remaining life of the mines. There is a diversity of practices in the mining industry in the treatment of drilling and other related costs to delineate new ore reserves. The Company follows the practices outlined in the next two paragraphs in its treatment of drilling and related costs. Drilling and other associated costs incurred in the Company’s efforts to delineate new resources, whether near-mine or Greenfield are expensed as incurred. These costs are classified as mineral exploration costs. Once the Company determines through feasibility studies that proven and probable reserves exist and that the drilling and other associated costs embody a probable future benefit that involves a capacity, singly or in combination with other assets, to contribute directly or indirectly to future net cash inflow, then the costs are classified as mine development costs. These mine development costs incurred prospectively to develop the property are capitalized as incurred, until the commencement of production, and are amortized using the units of production method over estimated life of the ore body. During the production stage, drilling and other related costs incurred to maintain production are included in production cost in the period in which they are incurred. Drilling and other related costs incurred in the Company’s efforts to delineate a major expansion of reserves at an existing production property are expensed as incurred. Once the Company determines through feasibility studies that proven and probable incremental reserves exist and that the drilling and other associated costs embody a probable future benefit that involves a capacity, singly or in combination with other assets, to contribute directly or indirectly to future net cash inflow, then the costs are classified as mine development costs. These incremental mine development costs are capitalized as incurred, until the commencement of production and amortized using the units of production method over the estimated life of the ore body. A major expansion of reserves is one that increases total reserves at a property by approximately 10%. For the years ended December 31, 2012, 2011 and 2010, the Company did not capitalize any drilling and related costs. The net balance of capitalized mine development costs at December 31, 2012 and 2011, were $37.9 million and $39.8 million, respectively.
Asset retirement obligations (reclamation and remediation costs)	The fair value of a liability for asset retirement obligations is recognized in the period in which the liability is incurred. The liability is measured at fair value and is adjusted to its present value in subsequent periods as accretion expense is recorded. The corresponding asset retirement costs are capitalized as part of the carrying value of the related long-lived assets and depreciated over the asset’s useful life.
Intangible assets	Intangible assets include primarily the excess amount paid over the book value for investment shares and mining and engineering development studies. Intangible assets are carried at acquisition costs, net of accumulated amortization and are amortized principally on a unit of production basis over the estimated remaining life of the mines. Intangible assets are reviewed for impairment whenever events or changes in circumstances indicate that the carrying amount of the asset may not be recoverable.
Debt issuance costs	Debt issuance costs, which are included in other assets, are amortized using the interest method over the term of the related debt.
Ore reserves	The Company periodically reevaluates estimates of its ore reserves, which represent the Company’s estimate as to the amount of unmined copper remaining in its existing mine locations that can be produced and sold at a profit. Such estimates are based on engineering evaluations derived from samples of drill holes and other openings, combined with assumptions about copper market prices and production costs at each of the respective mines. The Company updates its estimate of ore reserves at the beginning of each year. In this calculation the Company uses current metal prices which are defined as the average metal price over the preceding three years. The current price per pound of copper, as defined, was $3.68, $3.26 and $2.97 at the end of 2012, 2011 and 2010, respectively. The ore reserve estimates are used to determine the amortization of mine development and intangible assets. Once the Company determines through feasibility studies that proven and probable reserves exist and that the drilling and other associated costs embody a probable future benefit that involves a capacity, singly or in combination with other assets, to contribute directly or indirectly to future net cash inflow, then the costs are classified as mine development costs and the Company discloses the related ore reserves.
Exploration	Tangible and intangible costs incurred in the search for mineral properties are charged against earnings when incurred.
Income taxes	Provisions for income taxes are based on taxes payable or refundable for the current year and deferred taxes on temporary differences between the amount of taxable income and pretax financial income and between the tax bases of assets and liabilities and their reported amounts in the financial statements. Deferred tax assets and liabilities are included in the financial statements at currently enacted income tax rates applicable to the period in which the deferred tax assets and liabilities are expected to be realized and settled as prescribed in ASC 740 “Income tax.” As changes in tax laws or rates are enacted, deferred tax assets and liabilities are adjusted through the provision for income taxes. Deferred income tax assets are reduced by any benefits that, in the opinion of management, are more likely not to be realized. The Company classifies income tax-related interest and penalties as income taxes in the financial statements. The Company’s operations involve dealing with uncertainties and judgments in the application of complex tax regulations in multiple jurisdictions. The final taxes paid are dependent upon many factors, including negotiations with taxing authorities in various jurisdictions and resolution of disputes arising from federal, state, and international tax audits. The Company recognizes potential liabilities and records tax liabilities for anticipated tax audit issues in the U.S. and other tax jurisdictions based on its estimate of whether, and the extent to which, additional taxes will be due. The Company follows the guidance of ASC 740 “Income Tax” to record these liabilities. (See Note 7 “Income taxes” of the consolidated financial statements for additional information). The Company adjusts these reserves in light of changing facts and circumstances; however, due to the complexity of some of these uncertainties, the ultimate resolution may result in a payment that is materially different from the Company’s current estimate of the tax liabilities. If its estimate of tax liabilities proves to be less than the ultimate assessment, an additional charge to expense would result. If payment of these amounts ultimately proves to be less than the recorded amounts, the reversal of the liabilities would result in tax benefits being recognized in the period when the Company determines the liabilities are no longer necessary. The Company recognizes interest and penalties, if any, related to unrecognized tax benefits in income tax expense.
Foreign exchange	The Company’s functional currency is the U.S. dollar. As required by local law, both the Peruvian Branch and Minera Mexico maintain their books of accounts in Peruvian nuevos soles and Mexican pesos, respectively. Foreign currency assets and liabilities are remeasured into U.S. dollars at current exchange rates except for non-monetary items such as inventory, property, intangible assets and other assets which are remeasured at historical exchange rates. Revenues and expenses are generally translated at actual exchange rates in effect during the period, except for those items related to balance sheet amounts that are remeasured at historical exchange rates. Gains and losses from foreign currency remeasurement are included in earnings of the period. Gains and (losses) resulting from foreign currency transactions are included in “Cost of sales (exclusive of depreciation, amortization and depletion).”
Derivative instruments	The Company utilizes certain types of derivative financial instruments to enhance its ability to manage risks that exist as part of its ongoing business operations and to enhance its return on Company assets. Derivative contracts are reflected as assets or liabilities in the balance sheet at their fair value. The estimated fair value of the derivatives is based on market and/or dealer quotations and in certain cases valuation modeling. From time to time the Company has entered into copper and zinc swap contracts to protect a fixed copper and zinc price for portions of its metal sales, hedging contracts to fix power prices for a portion of its production costs, interest rate swap agreements to hedge the interest rate risk exposure on certain of its bank obligations with variable interest rates and currency swap arrangements to ensure Mexican peso/ U.S. dollar conversion rates. Gains and losses related to copper and zinc hedges are included in net sales, gain and losses related to power costs are included in cost of sales, all other gains and losses on derivative contracts are included in “Gain (loss) on derivative contracts” in the consolidated statement of earnings. The Company assesses the effectiveness of the derivative contracts periodically using either regression analysis or the dollar offset approach, both retrospectively and prospectively, to determine whether the hedging instruments have been highly effective in offsetting changes in fair value of the hedged items. Unrealized gains (losses) on cash flow derivatives that meet the requirements of hedge accounting are included in “other comprehensive income” in the consolidated balance sheet until settlement.
Asset impairments	The Company evaluates long-term assets when events or changes in economic circumstances indicate that the carrying amount of such assets may not be recoverable. These evaluations are based on business plans that are prepared using a time horizon that is reflective of the Company’s expectations of metal prices over its business cycle. The Company is currently using a long-term average copper price of $3.00 per pound of copper and an average molybdenum price of $12.00 per pound, reflective of the current price environment, for impairment tests. The results of its impairment tests using these long-term copper and molybdenum prices show no impairment in the carrying value of their assets. In recent years its assumptions for long-term average prices resulted in stricter evaluations for impairment analysis than would the higher three year average prices for copper and molybdenum prices. Should this situation reverse in the future with three year average prices below the long-term price assumption, the Company would assess the need to use the three year average prices in its evaluations. The Company uses an estimate of the future undiscounted net cash flows of the related asset or asset group over the remaining life to measure whether the assets are recoverable and measures any impairment by reference to fair value.
Other comprehensive income	Comprehensive income represents changes in equity during a period, except those resulting from investments by owners and distributions to owners. During the fiscal years ended December 31, 2012, 2011 and 2010, the components of “other comprehensive income (loss)” were the unrealized gain (loss) on cash flow hedge derivative instruments, the unrecognized gain (loss) on employee benefit obligations and realized gain (loss) included in net income.
Business segments	Company management views Southern Copper as having three reportable segments and manages it on the basis of these segments. The segments identified by the Company are: 1) the Peruvian operations, which include the two open-pit copper mines in Peru and the plants and services supporting such mines, 2) the Mexican open-pit copper mines, which include La Caridad and Buenavista mine complexes and their supporting facilities and 3) the Mexican underground mining operations, which include five underground mines that produce zinc, copper, silver and gold, a coal mine and a zinc refinery. The Chief Operating Officer of the Company focuses on operating income as measure of performance to evaluate different segments, and to make decisions to allocate resources to the reported segments.

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES: (Policies)

12 Months Ended

Dec. 31, 2012

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES:

The consolidated financial statements include the accounts of subsidiaries of which the Company has voting control, in accordance with Accounting Standards Codification 810 Consolidation. Such financial statements are prepared in accordance with accounting principles generally accepted in the United States (“U.S. GAAP”).

Use of estimates

The preparation of financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, and disclosure of contingent assets and liabilities at the date of the financial statements, and the reported amounts of revenues and expenses during the reporting period. Significant items subject to such estimates and assumptions include the carrying value of ore reserves that are the basis for future cash flow estimates and amortization calculations; environmental, reclamation, closure and retirement obligations; estimates of recoverable copper in mill and leach stockpiles; asset impairments (including estimates of future cash flows); bad debts; inventory obsolescence; deferred and current income tax; valuation allowances for deferred tax assets; reserves for contingencies and litigation; and fair value of financial instruments. Management bases its estimates on the Company’s historical experience and on various other assumptions that are believed to be reasonable under the circumstances. Actual results could differ from those estimates.

Revenue recognition

Substantially all of the Company’s copper is sold under annual or other longer-term contracts.

Revenue is recognized when title passes to the customer. The passing of title is based on terms of the contract, generally upon shipment. Copper revenue is determined based on the monthly average of prevailing commodity prices according to the terms of the contracts. The Company provides allowances for doubtful accounts based upon historical bad debt and claims experience and periodic evaluation of specific customer accounts.

For certain of the Company’s sales of copper and molybdenum products, customer contracts allow for pricing based on a month subsequent to shipping, in most cases within the following three months and occasionally in some cases a few additional months. In such cases, revenue is recorded at a provisional price at the time of shipment. The provisionally priced copper sales are adjusted to reflect forward LME or COMEX copper prices at the end of each month until a final adjustment is made to the price of the shipments upon settlement with customers pursuant to the terms of the contract. In the case of molybdenum sales, for which there are no published forward prices, the provisionally priced sales are adjusted to reflect the market prices at the end of each month until a final adjustment is made to the price of the shipments upon settlement with customers pursuant to the terms of the contract.

These provisional pricing arrangements are accounted for separately from the contract as an embedded derivative instrument under ASC 815-30 “Derivatives and Hedging — Cash Flow Hedges.” The Company sells copper in concentrate, anode, blister and refined form at industry standard commercial terms. Net sales include the invoiced value and corresponding fair value adjustment of the related forward contract of copper, zinc, silver, molybdenum, acid and other metals.

Shipping and handling fees and costs

Amounts billed to customers for shipping and handling are classified as sales. Amounts incurred for shipping and handling are included in cost of sales (exclusive of depreciation, amortization and depletion).

Cash and cash equivalents

Cash and cash equivalents include bank deposits, certificates of deposit and short-term investment funds with original maturities of three months or less at the date of purchase. The carrying value of cash and cash equivalents approximates fair value.

Short-term investments

The Company accounts for short-term investments in accordance with ASC 320-10 “Investments Debt and Equity Securities — Recognition.” The Company determines the appropriate classification of all short-term investments as held-to-maturity, available-for-sale or trading at the time of purchase and re-evaluates such classifications as of each balance sheet date. Unrealized gains and losses on available-for-sale investments, net of taxes, are reported as a component of accumulated other comprehensive income (loss) in stockholders’ equity, unless such loss is deemed to be other than temporary.

Inventories

Metal inventories, consisting of work—in-process and finished goods, are carried at the lower of average cost or market. Costs incurred in the production of metal inventories exclude general and administrative costs.

Work-in-process inventories represent materials that are in the process of being converted into a saleable product. Conversion processes vary depending on the nature of the copper ore and the specific mining operation. For sulfide ores, processing includes milling and concentrating and results in the production of copper and molybdenum concentrates.

Finished goods include saleable products (e.g., copper concentrates, copper anodes, copper cathodes, copper rod, molybdenum concentrate and other metallurgical products).

Supplies inventories are carried at the lower of average cost less a reserve for obsolescence or market.

Long-term inventory - Leachable material

The leaching process is an integral part of the mining operations carried out at the Company’s open-pit mines. The Company capitalizes the production cost of leachable material at its Toquepala, La Caridad and Buenavista mines recognizing it as inventory. The estimates of recoverable mineral content contained in the leaching dumps are supported by engineering studies. As the production cycle of the leaching process is significantly longer than the conventional process of concentrating, smelting and electrolytic refining, the Company includes on its balance sheet, current leach inventory (included in work-in-process inventories) and long-term leach inventory. The cost attributed to the leach material is charged to cost of sales generally over a five-year period (the average estimated recovery period based on the historical recovery percentages of each mine).

Property

Property is recorded at acquisition cost, net of accumulated depreciation and amortization. Cost includes major expenditures for improvements and replacements, which extend useful lives or increase capacity and interest costs associated with significant capital additions. Maintenance, repairs, normal development costs at existing mines, and gains or losses on assets retired or sold are reflected in earnings as incurred.

Buildings and equipment are depreciated on the straight-line method over estimated lives from five to 40 years or the estimated life of the mine if shorter.

Mine development

Mine development includes primarily the cost of acquiring land rights to an exploitable ore body, pre-production stripping costs at new mines that are commercially exploitable, costs associated with bringing new mineral properties into production, and removal of overburden to prepare unique and identifiable areas outside the current mining area for such future production. Mine development costs are amortized on a unit of production basis over the remaining life of the mines.

There is a diversity of practices in the mining industry in the treatment of drilling and other related costs to delineate new ore reserves. The Company follows the practices outlined in the next two paragraphs in its treatment of drilling and related costs.

Drilling and other associated costs incurred in the Company’s efforts to delineate new resources, whether near-mine or Greenfield are expensed as incurred. These costs are classified as mineral exploration costs. Once the Company determines through feasibility studies that proven and probable reserves exist and that the drilling and other associated costs embody a probable future benefit that involves a capacity, singly or in combination with other assets, to contribute directly or indirectly to future net cash inflow, then the costs are classified as mine development costs. These mine development costs incurred prospectively to develop the property are capitalized as incurred, until the commencement of production, and are amortized using the units of production method over estimated life of the ore body. During the production stage, drilling and other related costs incurred to maintain production are included in production cost in the period in which they are incurred.

Drilling and other related costs incurred in the Company’s efforts to delineate a major expansion of reserves at an existing production property are expensed as incurred. Once the Company determines through feasibility studies that proven and probable incremental reserves exist and that the drilling and other associated costs embody a probable future benefit that involves a capacity, singly or in combination with other assets, to contribute directly or indirectly to future net cash inflow, then the costs are classified as mine development costs. These incremental mine development costs are capitalized as incurred, until the commencement of production and amortized using the units of production method over the estimated life of the ore body. A major expansion of reserves is one that increases total reserves at a property by approximately 10%.

For the years ended December 31, 2012, 2011 and 2010, the Company did not capitalize any drilling and related costs. The net balance of capitalized mine development costs at December 31, 2012 and 2011, were $37.9 million and $39.8 million, respectively.

Asset retirement obligations (reclamation and remediation costs)

The fair value of a liability for asset retirement obligations is recognized in the period in which the liability is incurred. The liability is measured at fair value and is adjusted to its present value in subsequent periods as accretion expense is recorded. The corresponding asset retirement costs are capitalized as part of the carrying value of the related long-lived assets and depreciated over the asset’s useful life.

Intangible assets

Intangible assets include primarily the excess amount paid over the book value for investment shares and mining and engineering development studies. Intangible assets are carried at acquisition costs, net of accumulated amortization and are amortized principally on a unit of production basis over the estimated remaining life of the mines. Intangible assets are reviewed for impairment whenever events or changes in circumstances indicate that the carrying amount of the asset may not be recoverable.

Debt issuance costs

Debt issuance costs, which are included in other assets, are amortized using the interest method over the term of the related debt.

Ore reserves

The Company periodically reevaluates estimates of its ore reserves, which represent the Company’s estimate as to the amount of unmined copper remaining in its existing mine locations that can be produced and sold at a profit. Such estimates are based on engineering evaluations derived from samples of drill holes and other openings, combined with assumptions about copper market prices and production costs at each of the respective mines.

The Company updates its estimate of ore reserves at the beginning of each year. In this calculation the Company uses current metal prices which are defined as the average metal price over the preceding three years. The current price per pound of copper, as defined, was $3.68, $3.26 and $2.97 at the end of 2012, 2011 and 2010, respectively. The ore reserve estimates are used to determine the amortization of mine development and intangible assets.

Once the Company determines through feasibility studies that proven and probable reserves exist and that the drilling and other associated costs embody a probable future benefit that involves a capacity, singly or in combination with other assets, to contribute directly or indirectly to future net cash inflow, then the costs are classified as mine development costs and the Company discloses the related ore reserves.

Exploration

Tangible and intangible costs incurred in the search for mineral properties are charged against earnings when incurred.

Income taxes

Provisions for income taxes are based on taxes payable or refundable for the current year and deferred taxes on temporary differences between the amount of taxable income and pretax financial income and between the tax bases of assets and liabilities and their reported amounts in the financial statements. Deferred tax assets and liabilities are included in the financial statements at currently enacted income tax rates applicable to the period in which the deferred tax assets and liabilities are expected to be realized and settled as prescribed in ASC 740 “Income tax.” As changes in tax laws or rates are enacted, deferred tax assets and liabilities are adjusted through the provision for income taxes. Deferred income tax assets are reduced by any benefits that, in the opinion of management, are more likely not to be realized.

The Company classifies income tax-related interest and penalties as income taxes in the financial statements.

The Company’s operations involve dealing with uncertainties and judgments in the application of complex tax regulations in multiple jurisdictions. The final taxes paid are dependent upon many factors, including negotiations with taxing authorities in various jurisdictions and resolution of disputes arising from federal, state, and international tax audits. The Company recognizes potential liabilities and records tax liabilities for anticipated tax audit issues in the U.S. and other tax jurisdictions based on its estimate of whether, and the extent to which, additional taxes will be due. The Company follows the guidance of ASC 740 “Income Tax” to record these liabilities. (See Note 7 “Income taxes” of the consolidated financial statements for additional information). The Company adjusts these reserves in light of changing facts and circumstances; however, due to the complexity of some of these uncertainties, the ultimate resolution may result in a payment that is materially different from the Company’s current estimate of the tax liabilities. If its estimate of tax liabilities proves to be less than the ultimate assessment, an additional charge to expense would result. If payment of these amounts ultimately proves to be less than the recorded amounts, the reversal of the liabilities would result in tax benefits being recognized in the period when the Company determines the liabilities are no longer necessary. The Company recognizes interest and penalties, if any, related to unrecognized tax benefits in income tax expense.

Foreign exchange

The Company’s functional currency is the U.S. dollar. As required by local law, both the Peruvian Branch and Minera Mexico maintain their books of accounts in Peruvian nuevos soles and Mexican pesos, respectively.

Foreign currency assets and liabilities are remeasured into U.S. dollars at current exchange rates except for non-monetary items such as inventory, property, intangible assets and other assets which are remeasured at historical exchange rates. Revenues and expenses are generally translated at actual exchange rates in effect during the period, except for those items related to balance sheet amounts that are remeasured at historical exchange rates. Gains and losses from foreign currency remeasurement are included in earnings of the period.

Gains and (losses) resulting from foreign currency transactions are included in “Cost of sales (exclusive of depreciation, amortization and depletion).”

Derivative instruments

The Company utilizes certain types of derivative financial instruments to enhance its ability to manage risks that exist as part of its ongoing business operations and to enhance its return on Company assets. Derivative contracts are reflected as assets or liabilities in the balance sheet at their fair value. The estimated fair value of the derivatives is based on market and/or dealer quotations and in certain cases valuation modeling. From time to time the Company has entered into copper and zinc swap contracts to protect a fixed copper and zinc price for portions of its metal sales, hedging contracts to fix power prices for a portion of its production costs, interest rate swap agreements to hedge the interest rate risk exposure on certain of its bank obligations with variable interest rates and currency swap arrangements to ensure Mexican peso/ U.S. dollar conversion rates. Gains and losses related to copper and zinc hedges are included in net sales, gain and losses related to power costs are included in cost of sales, all other gains and losses on derivative contracts are included in “Gain (loss) on derivative contracts” in the consolidated statement of earnings.

The Company assesses the effectiveness of the derivative contracts periodically using either regression analysis or the dollar offset approach, both retrospectively and prospectively, to determine whether the hedging instruments have been highly effective in offsetting changes in fair value of the hedged items.

Unrealized gains (losses) on cash flow derivatives that meet the requirements of hedge accounting are included in “other comprehensive income” in the consolidated balance sheet until settlement.

Asset impairments

The Company evaluates long-term assets when events or changes in economic circumstances indicate that the carrying amount of such assets may not be recoverable. These evaluations are based on business plans that are prepared using a time horizon that is reflective of the Company’s expectations of metal prices over its business cycle. The Company is currently using a long-term average copper price of $3.00 per pound of copper and an average molybdenum price of $12.00 per pound, reflective of the current price environment, for impairment tests. The results of its impairment tests using these long-term copper and molybdenum prices show no impairment in the carrying value of their assets.

In recent years its assumptions for long-term average prices resulted in stricter evaluations for impairment analysis than would the higher three year average prices for copper and molybdenum prices. Should this situation reverse in the future with three year average prices below the long-term price assumption, the Company would assess the need to use the three year average prices in its evaluations. The Company uses an estimate of the future undiscounted net cash flows of the related asset or asset group over the remaining life to measure whether the assets are recoverable and measures any impairment by reference to fair value.

Other comprehensive income

Comprehensive income represents changes in equity during a period, except those resulting from investments by owners and distributions to owners. During the fiscal years ended December 31, 2012, 2011 and 2010, the components of “other comprehensive income (loss)” were the unrealized gain (loss) on cash flow hedge derivative instruments, the unrecognized gain (loss) on employee benefit obligations and realized gain (loss) included in net income.

Business segments

Company management views Southern Copper as having three reportable segments and manages it on the basis of these segments. The segments identified by the Company are: 1) the Peruvian operations, which include the two open-pit copper mines in Peru and the plants and services supporting such mines, 2) the Mexican open-pit copper mines, which include La Caridad and Buenavista mine complexes and their supporting facilities and 3) the Mexican underground mining operations, which include five underground mines that produce zinc, copper, silver and gold, a coal mine and a zinc refinery.

The Chief Operating Officer of the Company focuses on operating income as measure of performance to evaluate different segments, and to make decisions to allocate resources to the reported segments.