Accounting policies	12 Months Ended
Dec. 31, 2012
Accounting policies [Abstract]
Accounting policies	Note 2- Accounting policies Use of estimates Preparation of financial statements in accordance with accounting principles generally accepted in the United States 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. Actual results could differ from those estimates. Contract revenue A substantial majority of the Company's revenues are derived from dayrate based drilling contracts (which may include lump sum fees for mobilization and demobilization) and other service contracts. Both dayrate based and lump sum fee revenues are recognized ratably over the contract period when services are rendered. Under some contracts, the Company is entitled to additional payments for meeting or exceeding certain performance targets. Such additional payments are recognized when any uncertainties are resolved or upon completion of the drilling program. In connection with drilling contracts, the Company may receive lump sum fees for the mobilization of equipment and personnel or for capital additions and upgrades prior to commencement of drilling services. These up-front fees are recognized as revenue over the contract term, excluding option periods. In some cases, the Company may receive lump sum non-contingent fees or dayrate based fees from customers for demobilization upon completion of a drilling contract. Non-contingent demobilization fees are recognized as revenue over contract term, excluding option periods not exercised by our customers. Contingent demobilization fees are recognized as earned upon completion of the drilling contract. Fees received from customers under drilling contracts for capital upgrades are deferred and recognized over the contract term, excluding option periods not exercised. Reimbursables Reimbursements received for the purchases of supplies, personnel services and other services provided on behalf of and at the request of our customers in accordance with a contract or agreement are recorded as revenue. The related costs are recorded as reimbursable expenses in the same period. Other revenues In a business combination there may exist favorable and unfavorable drilling contracts which are recorded at fair value at the date of acquisition. A favorable or unfavorable drilling contract is a contract that has a dayrate which differs from prevailing market rates at the time of acquisition. The net present value of such contracts is recorded as an asset or liability at the purchase date and subsequently recognized as revenue or reduction to revenue over the contract term. Mobilization and demobilization expenses Demobilization costs are costs related to the transfer of a vessel or drilling rig to a safe harbor or different geographic area and are expensed as incurred. Mobilization costs incurred as part of a contract are capitalized and recognized as expense over the contract term, excluding option periods not exercised by our customers. The costs of relocating drilling units that are not under contract are expensed as incurred. Rig Operating Expenses Rig operating expenses are costs associated with operating a drilling rig that is either in operation or stacked, and include the remuneration of offshore crews and related costs, rig supplies, insurance costs, expenses for repairs and maintenance as well as costs related to onshore personnel in various locations where we operate the rigs and are expensed as incurred. Repairs, maintenance and periodic surveys Costs related to periodic overhauls of drilling units are capitalized under drilling units and amortized over the anticipated period between overhauls, which is generally five years. Related costs are primarily yard costs and the cost of employees directly involved in the work. Amortization costs for periodic overhauls are included in depreciation and amortization expense. Costs for other repair and maintenance activities are included in vessel and rig operating expenses and are expensed as incurred. Foreign currencies The Company and the majority of its subsidiaries use the U.S. dollars as their functional currency because the majority of their revenues and expenses are denominated in U.S. dollars. Accordingly, the Company's reporting currency is also U.S. dollars. For subsidiaries that maintain their accounts in currencies other than U.S. dollars, the Company uses the current method of translation whereby the statements of operations are translated using the average exchange rate for the year and the assets and liabilities are translated using the year end exchange rate. Foreign currency translation gains or losses on consolidation are recorded as a separate component of other comprehensive income in shareholders' equity. Transactions in foreign currencies are translated into U.S. dollars at the rates of exchange in effect at the date of the transaction. Foreign currency assets and liabilities are translated using rates of exchange at the balance sheet date. Gains and losses on foreign currency transactions are included in the consolidated statements of operations. Current and non-current classification Receivables and liabilities are classified as current assets and liabilities respectively, if their maturity is within one year of the balance sheet date. Otherwise, they are classified as non-current assets and liabilities. Cash and cash equivalents Cash and cash equivalents consist of cash, bank deposits and highly liquid financial instruments with original maturities of three months or less. Restricted cash Restricted cash consists of bank deposits which have been pledged as collateral for certain guarantees issued by a bank or minimum deposits which must be maintained in accordance with contractual arrangements. Restricted cash with maturity longer than one year are classified as non-current assets. Marketable securities Marketable equity securities held by the Company are considered to be available-for-sale and, as such, are recorded at fair value with resulting unrealized gains and losses recorded as a separate component of accumulated other comprehensive income in shareholders' equity. The Company also holds marketable securities considered to be trading securities and as such, are recorded at fair value with resulting unrealized gains and losses recorded through the profit and loss statement. Gains and losses on forward contracts to purchase marketable equity securities that do not meet the definition of a derivative are accounted for as available-for-sale. Receivables Receivables, including accounts receivable, are recorded in the balance sheet at their nominal amount less an allowance for doubtful accounts. The Company establishes reserves for doubtful accounts on a case-by-case basis when it is unlikely that required payments of specific amounts will occur. In establishing these reserves, the Company considers the financial condition of the customer as well as specific circumstances related to the receivable such as customer disputes. Receivable amounts determined as being unrecoverable are written off. Impairment of marketable securities and equity method investees The Company analyzes its available-for-sale securities and equity method investees for impairment at each reporting period to evaluate whether an event or change in circumstances has occurred in that period that may have a significant adverse effect on the value of the investment. The Company records an impairment charge for other-than-temporary declines in value when the value is not anticipated to recover above cost within reasonably period after the measurement date, unless there are mitigating factors that indicate impairment may not be required. If an impairment charge is recorded, subsequent recoveries in value are not reflected in earnings until sale of the securities held as available for sale or of the equity method investee are sold. Newbuildings The carrying value of rigs under construction ("Newbuildings") represents the accumulated costs at the balance sheet date. Cost components include payments for yard installments and variation orders, construction supervision, equipment, spare parts, capitalized interest, costs related to first time mobilization and commissioning costs. No charge for depreciation is made until commissioning of the newbuilding has been completed and it is ready for its intended use. The Company may have option agreements with shipyards to order new rigs at fixed or variable prices which require some or no additional payment upon exercise. Payments for rig purchase options are capitalized at the time when option contracts are acquired or entered into. The Company reviews the expected future cash flows, which would result from the exercise of each option contract on a contract by contract basis to determine whether the carrying value of the option is recoverable. Capitalized interest Interest expenses are capitalized during construction of newbuildings based on accumulated expenditures for the applicable project at the Company's current rate of borrowing. The amount of interest expense capitalized in an accounting period shall be determined by applying an interest rate ("the capitalization rate") to the average amount of accumulated expenditures for the asset during the period. The capitalization rates used in an accounting period shall be based on the rates applicable to borrowings outstanding during the period. The Company does not capitalize amounts beyond the actual interest expense incurred in the period. If the Company's financing plans associate a specific new borrowing with a qualifying asset, the Company uses the rate on that borrowing as the capitalization rate to be applied to that portion of the average accumulated expenditures for the asset that does not exceed the amount of that borrowing. If average accumulated expenditures for the asset exceed the amounts of specific new borrowings associated with the asset, the capitalization rate to be applied to such excess shall be a weighted average of the rates applicable to other borrowings of the Company. Drilling units Rigs, vessels and equipment are recorded at historical cost less accumulated depreciation. The cost of these assets, less estimated residual value is depreciated on a straight-line basis over their estimated remaining economic useful lives. The estimated economic useful life of the Company's floaters, jack-up rigs and tender rigs, when new, is 30 years. Significant investments are capitalized and depreciated in accordance with the nature of the investment. Significant investments that are deemed to increase an asset's value for its remaining useful life are capitalized and depreciated over the remaining life of the asset. Assets are classified as held for sale when all of the following criteria are met, which are as follows: Management, having the authority to approve the action, commits to a plan to sell the asset (disposal group), the asset (disposal group) is available for immediate sale in its present condition subject only to terms that are usual and customary for sales of such assets (disposal groups), an active program to locate a buyer and other actions required to complete the plan to sell the asset (disposal group) have been initiated, the sale of the asset (disposal group) is probable, and transfer of the asset (disposal group) is expected to qualify for recognition as a completed sale, within one year. The term probable refers to a future sale that is likely to occur, the asset (disposal group) is being actively marketed for sale at a price that is reasonable in relation to its current fair value and actions required to complete the plan indicate that it is unlikely that significant changes to the plan will be made or that the plan will be withdrawn. Cost of property and equipment sold or retired, with the related accumulated depreciation and write-downs are removed from the balance sheet, and resulting gains or losses are included in the consolidated statement of operations. Equipment Equipment is recorded at historical cost less accumulated depreciation and is depreciated over its estimated remaining useful life, which is between three and five years depending on the type of asset. Goodwill The Company allocates the purchase price of acquired businesses to the identifiable tangible and intangible assets and liabilities acquired, with any remaining amount being recorded as goodwill. Goodwill is tested for impairment at least annually at the reporting unit level, which is defined as an operating segment or a component of an operating segment that constitutes a business for which financial information is available and is regularly reviewed by management. The Company has determined that its reporting units are the same as its operating segments for the purpose of allocating goodwill and the subsequent testing of goodwill for impairment. The Company first assesses qualitative factors to determine whether it is more likely than not that the fair value of a reporting unit is less than its carrying amount as a basis for determining whether it is necessary to perform the two step goodwill impairment test. If the qualitative factors indicate possible impairment, the standard requires the Company to compare the fair value of its reporting units to their carrying value. In the event that the fair value is less than carrying value, the Company must perform an exercise similar to a purchase price allocation in a business combination in order to determine the amount of the impairment charge. The goodwill impairment test for a reporting unit is based on discounted cash flows. The Company uses estimated future cash flows applying contract dayrates during the firm contract periods and estimated forecasted dayrates for the periods after expiry of firm contract periods. Zero escalation of dayrates for the periods will be assumed. The estimated future cash flows will be based on remaining economic useful lives for the assets, and discounted using a weighted average cost of capital (WACC). Other intangible assets Other intangible assets are recorded at historical cost less accumulated amortization. The cost of these assets less estimated residual value is amortized on a straight-line basis over the estimated remaining economic useful lives. Other intangible assets include technology and customer relationships. Impairment of long-lived assets The carrying value of long-lived assets that are held and used by the Company are reviewed for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may no longer be appropriate. The Company assesses recoverability of the carrying value of the asset by estimating the undiscounted future net cash flows expected to result from the asset, including eventual disposition. If the undiscounted future net cash flows are less than the carrying value of the asset, an impairment is made to the market value or the discounted future net cash flows. Defined benefit pension plans The Company has several defined benefit plans which provide retirement, death and early termination benefits. The Company's net obligation is calculated separately for each plan by estimating the amount of the future benefit that employees have earned in return for their cumulative service. The aggregated projected future benefit obligation is discounted to a present value, and the aggregated fair value of any plan assets is deducted. The discount rate is the market yield at the balance sheet date on government bonds in the relevant currency and based on terms consistent with the post-employment benefit obligations. The retirement benefits are generally a function of number of years of employment and amount of employees' remuneration. The plans are primarily funded through payments to insurance companies. The Company records its pension costs in the period during which the services are rendered by the employees. Actuarial gains and losses are recognized in the statement of operations when the net cumulative unrecognized actuarial gains or losses for each individual plan at the end of the previous reporting year exceed 10 percent of the higher of the present value of the defined benefit obligation and the fair value of plan assets at that date. These gains and losses are recognized over the expected remaining working lives of the employees participating in the plans. Otherwise, recognition of actuarial gains and losses is included in other comprehensive income. Those amounts will be subsequently recognized as a component of net periodic pension cost on the same basis as the amounts recognized in accumulated other comprehensive income. Treasury shares Treasury shares are recognized at cost as a component of equity. The purchase of treasury shares reduces the Company's share capital by the nominal value of the acquired treasury shares. The amount paid in excess of the nominal value is treated as a reduction of additional paid-in capital. Derivative Financial Instruments and Hedging Activities The Company's interest-rate swap agreements, foreign currency options and forward exchange contracts are recorded at fair value. Changes in the fair value of interest-rate swap agreements, forward exchange and currency options contracts, which have not been designated as hedging instruments, are recorded as a gain or loss as a separate line item within Financial Items. Changes in the fair value of any derivative instrument that we have formally designated as a hedge, are recognized in Accumulated other comprehensive income (loss) in the Consolidated Balance Sheets. Any change in fair value relating to an ineffective portion of a designated hedge is recognized, in the Consolidated Statement of Operations. When the hedged item affects the income statement, the gain or loss included in accumulated other comprehensive income is reported on the same line in the Consolidated Statements of Operations as the hedged item. Financial instruments such as forward contracts to purchase shares that do not qualify as derivative instruments are not recognized on the balance sheet, unless deemed impaired. Such instruments are off-balance sheet transactions and result in only disclosures to the financial statements. Income taxes Seadrill is a Bermuda company. Currently, Seadrill is not required to pay taxes in Bermuda on ordinary income or capital gains as we qualify as an exempt company. The Company has received written assurance from the Minister of Finance in Bermuda that it will be exempt from taxation until March 2035. Certain subsidiaries operate in other jurisdictions where taxes are imposed. Consequently income taxes have been recorded in these jurisdictions when appropriate. Significant judgment is involved in determining the provision for income taxes. There are certain transactions for which the ultimate tax determination is unclear due to uncertainty in the ordinary course of business. Seadrill recognizes tax liabilities based on its assessment of whether its tax positions are more likely than not sustainable, based on the technical merits and considerations of the relevant taxing authority's widely understood administrative practices and precedence. Income tax expense consists of taxes currently payable and changes in deferred tax assets and liabilities calculated according to local tax rules. Deferred tax assets and liabilities are based on temporary differences that arise between carrying values used for financial reporting purposes and amounts used for taxation purposes of assets and liabilities and the future tax benefits of tax loss carry forwards. A deferred tax asset is recognized only to the extent that it is more likely than not that future taxable profits will be available against which the asset can be utilized. The amount of deferred tax provided is based upon the expected manner of settlement of the carrying amount of assets and liabilities, using tax rates enacted at the balance sheet date. The impact of tax law changes is recognized in periods when the change is enacted. Deferred charges Loan related costs, including debt arrangement fees, are capitalized and amortized over the term of the related loan and are included in interest expense. Convertible debt Convertible bond loans issued by the Company include both a loan component (host contract) and an option to convert the loan to shares (embedded derivative). An embedded derivative, such as a conversion option, may be separated from its host contract and accounted for separately if certain criteria are met (including if the contract that embodies both the embedded derivative and the host contract is not measured at fair value, the economic characteristics and risks of the embedded derivative instrument are not clearly and closely related to the economic characteristics and risks of the host contract and if a separate instrument with the same terms as the embedded instrument would be a derivative). If an embedded derivative instrument is separated from its host contract, the host contract shall be accounted for based on generally accepted accounting principles applicable to instruments of that type which do not contain embedded derivative instruments. Total Return Equity Swaps From time to time, the Company enters into total return equity swaps ("TRS") indexed to the Company's own shares, where the counterparty acquires shares in the Company and the Company carries the risk of fluctuations in the share price of the acquired shares. The fair value of each TRS is recorded as an asset or liability, with the changes in fair value recorded in the consolidated statement of operations. The Company may, from time to time, enter into TRS arrangements indexed to shares in other companies which are accounted for in a similar manner. Share-based compensation The Company has established an employee share ownership plan under which employees, directors and officers of the Group may be allocated options to subscribe for new shares in the ultimate parent, Seadrill Limited. The compensation cost for share options is recognized as an expense over the service period based on the fair value of the options granted. The fair value of the share options issued under the Company's employee share option plans is determined at grant date taking into account the terms and conditions upon which the options are granted, and using a valuation technique that is consistent with generally accepted valuation methodologies for pricing financial instruments, and that incorporates all factors and assumptions that knowledgeable, willing market participants would consider in determining fair value. The fair value of the share options is recognized as personnel expenses with a corresponding increase in equity over the period during which the employees become unconditionally entitled to the options. Compensation cost is initially recognized based upon options expected to vest with appropriate adjustments to reflect actual forfeitures. National insurance contributions arising from such incentive programs are expensed when the options are exercised. Provisions A provision is recognized in the balance sheet when the Company has a present legal or constructive obligation as a result of a past event, and it is probable that an outflow of economic benefits will be required to settle the obligation and a reliable estimate of the amount can be made. If the effect is material, provisions are determined by discounting the expected future cash flows at a pre-tax rate that reflects current market assessments of the time value of money and, where appropriate, the risks specific to the liability. Segment reporting We have in 2011 and 2012 significantly expanded our fleet of drilling rigs through acquisitions of new rigs and newbuilding orders. In response to this development we reviewed our internal reporting structure including the operating and reporting business segments in 2011. The review resulted in a change in our reporting segments with effect from January 1, 2011. As of December 31, 2012, the Company has three reportable business segments which include floaters, jack-up rigs and tender rigs. The well services business segment included the activities of Archer which performs various services related to platform drilling, drilling facility engineering, well intervention and oilfield services. With effect from the end of February 2011, Archer has been deconsolidated and the well services segment is no longer part of our consolidated financial statements. Related parties Parties are related if one party has the ability, directly or indirectly, to control the other party or exercise significant influence over the other party in making financial and operating decisions. Parties are also related if they are subject to common control or common significant influence. All transactions between the related parties are based on the principle of arm's length. Earnings per share Basic earnings per share ("EPS") is calculated based on the income (loss) for the period available to common stockholders divided by the weighted average number of shares outstanding for basic EPS for the period. Diluted EPS includes the effect of the assumed conversion of potentially dilutive instruments which for the Company includes share options and convertible debt. The determination of dilutive earnings per share requires the Company to potentially make certain adjustments to net income and for the weighted average shares outstanding used to compute basic earnings per share unless anti-dilutive. Reclassifications Certain reclassifications have been made to prior period amounts to conform to the current year presentation. These reclassifications did not have a material effect on the consolidated financial statements (refer to the Basis of preparation stated above). Recently Issued Accounting Standards Balance sheet—Effective January 1, 2013, we will adopt the accounting standards update that expands the disclosure requirements for the offsetting of assets and liabilities related to certain financial instruments and derivative instruments. The update requires disclosures to present both gross information and net information for financial instruments and derivative instruments that are eligible for net presentation due to a right of offset, an enforceable master netting arrangement or similar agreement. The update is effective for interim and annual periods beginning on or after January 1, 2013. We do not expect that our adoption will have a material effect on our consolidated balance sheet. Balance sheet—Effective January 1, 2013, we will adopt the accounting standards update that requires an entity to report the effect of significant reclassifications out of accumulated other comprehensive income on the respective line items in net income if the amount being reclassified is required under U.S. generally accepted accounting principles (GAAP) to be reclassified in its entirety to net income. For other amounts that are not required under U.S. GAAP to be reclassified in their entirety to net income in the same reporting period, an entity is required to cross-reference other disclosures required under U.S. GAAP that provide additional detail about those amounts. For public entities, the amendments are effective prospectively for reporting periods beginning after December 15, 2012. We do not expect that our adoption will have a material effect on our financial statements.

Note 2- Accounting policies

Use of estimates

Preparation of financial statements in accordance with accounting principles generally accepted in the United States 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. Actual results could differ from those estimates.

Contract revenue

A substantial majority of the Company's revenues are derived from dayrate based drilling contracts (which may include lump sum fees for mobilization and demobilization) and other service contracts. Both dayrate based and lump sum fee revenues are recognized ratably over the contract period when services are rendered. Under some contracts, the Company is entitled to additional payments for meeting or exceeding certain performance targets. Such additional payments are recognized when any uncertainties are resolved or upon completion of the drilling program.

In connection with drilling contracts, the Company may receive lump sum fees for the mobilization of equipment and personnel or for capital additions and upgrades prior to commencement of drilling services. These up-front fees are recognized as revenue over the contract term, excluding option periods.

In some cases, the Company may receive lump sum non-contingent fees or dayrate based fees from customers for demobilization upon completion of a drilling contract. Non-contingent demobilization fees are recognized as revenue over contract term, excluding option periods not exercised by our customers. Contingent demobilization fees are recognized as earned upon completion of the drilling contract.

Fees received from customers under drilling contracts for capital upgrades are deferred and recognized over the contract term, excluding option periods not exercised.

Reimbursables

Reimbursements received for the purchases of supplies, personnel services and other services provided on behalf of and at the request of our customers in accordance with a contract or agreement are recorded as revenue. The related costs are recorded as reimbursable expenses in the same period.

Other revenues

In a business combination there may exist favorable and unfavorable drilling contracts which are recorded at fair value at the date of acquisition. A favorable or unfavorable drilling contract is a contract that has a dayrate which differs from prevailing market rates at the time of acquisition. The net present value of such contracts is recorded as an asset or liability at the purchase date and subsequently recognized as revenue or reduction to revenue over the contract term.

Mobilization and demobilization expenses

Demobilization costs are costs related to the transfer of a vessel or drilling rig to a safe harbor or different geographic area and are expensed as incurred.

Mobilization costs incurred as part of a contract are capitalized and recognized as expense over the contract term, excluding option periods not exercised by our customers. The costs of relocating drilling units that are not under contract are expensed as incurred.

Rig Operating Expenses

Rig operating expenses are costs associated with operating a drilling rig that is either in operation or stacked, and include the remuneration of offshore crews and related costs, rig supplies, insurance costs, expenses for repairs and maintenance as well as costs related to onshore personnel in various locations where we operate the rigs and are expensed as incurred.

Repairs, maintenance and periodic surveys

Costs related to periodic overhauls of drilling units are capitalized under drilling units and amortized over the anticipated period between overhauls, which is generally five years. Related costs are primarily yard costs and the cost of employees directly involved in the work. Amortization costs for periodic overhauls are included in depreciation and amortization expense. Costs for other repair and maintenance activities are included in vessel and rig operating expenses and are expensed as incurred.

Foreign currencies

The Company and the majority of its subsidiaries use the U.S. dollars as their functional currency because the majority of their revenues and expenses are denominated in U.S. dollars. Accordingly, the Company's reporting currency is also U.S. dollars. For subsidiaries that maintain their accounts in currencies other than U.S. dollars, the Company uses the current method of translation whereby the statements of operations are translated using the average exchange rate for the year and the assets and liabilities are translated using the year end exchange rate. Foreign currency translation gains or losses on consolidation are recorded as a separate component of other comprehensive income in shareholders' equity.

Transactions in foreign currencies are translated into U.S. dollars at the rates of exchange in effect at the date of the transaction. Foreign currency assets and liabilities are translated using rates of exchange at the balance sheet date. Gains and losses on foreign currency transactions are included in the consolidated statements of operations.

Current and non-current classification

Receivables and liabilities are classified as current assets and liabilities respectively, if their maturity is within one year of the balance sheet date. Otherwise, they are classified as non-current assets and liabilities.

Cash and cash equivalents

Cash and cash equivalents consist of cash, bank deposits and highly liquid financial instruments with original maturities of three months or less.

Restricted cash

Restricted cash consists of bank deposits which have been pledged as collateral for certain guarantees issued by a bank or minimum deposits which must be maintained in accordance with contractual arrangements. Restricted cash with maturity longer than one year are classified as non-current assets.

Marketable securities

Marketable equity securities held by the Company are considered to be available-for-sale and, as such, are recorded at fair value with resulting unrealized gains and losses recorded as a separate component of accumulated other comprehensive income in shareholders' equity. The Company also holds marketable securities considered to be trading securities and as such, are recorded at fair value with resulting unrealized gains and losses recorded through the profit and loss statement. Gains and losses on forward contracts to purchase marketable equity securities that do not meet the definition of a derivative are accounted for as available-for-sale.

Receivables

Receivables, including accounts receivable, are recorded in the balance sheet at their nominal amount less an allowance for doubtful accounts. The Company establishes reserves for doubtful accounts on a case-by-case basis when it is unlikely that required payments of specific amounts will occur. In establishing these reserves, the Company considers the financial condition of the customer as well as specific circumstances related to the receivable such as customer disputes. Receivable amounts determined as being unrecoverable are written off.

Impairment of marketable securities and equity method investees

The Company analyzes its available-for-sale securities and equity method investees for impairment at each reporting period to evaluate whether an event or change in circumstances has occurred in that period that may have a significant adverse effect on the value of the investment. The Company records an impairment charge for other-than-temporary declines in value when the value is not anticipated to recover above cost within reasonably period after the measurement date, unless there are mitigating factors that indicate impairment may not be required. If an impairment charge is recorded, subsequent recoveries in value are not reflected in earnings until sale of the securities held as available for sale or of the equity method investee are sold.

Newbuildings

The carrying value of rigs under construction ("Newbuildings") represents the accumulated costs at the balance sheet date. Cost components include payments for yard installments and variation orders, construction supervision, equipment, spare parts, capitalized interest, costs related to first time mobilization and commissioning costs. No charge for depreciation is made until commissioning of the newbuilding has been completed and it is ready for its intended use.

The Company may have option agreements with shipyards to order new rigs at fixed or variable prices which require some or no additional payment upon exercise. Payments for rig purchase options are capitalized at the time when option contracts are acquired or entered into. The Company reviews the expected future cash flows, which would result from the exercise of each option contract on a contract by contract basis to determine whether the carrying value of the option is recoverable.

Capitalized interest

Interest expenses are capitalized during construction of newbuildings based on accumulated expenditures for the applicable project at the Company's current rate of borrowing. The amount of interest expense capitalized in an accounting period shall be determined by applying an interest rate ("the capitalization rate") to the average amount of accumulated expenditures for the asset during the period. The capitalization rates used in an accounting period shall be based on the rates applicable to borrowings outstanding during the period. The Company does not capitalize amounts beyond the actual interest expense incurred in the period.

If the Company's financing plans associate a specific new borrowing with a qualifying asset, the Company uses the rate on that borrowing as the capitalization rate to be applied to that portion of the average accumulated expenditures for the asset that does not exceed the amount of that borrowing. If average accumulated expenditures for the asset exceed the amounts of specific new borrowings associated with the asset, the capitalization rate to be applied to such excess shall be a weighted average of the rates applicable to other borrowings of the Company.

Drilling units

Rigs, vessels and equipment are recorded at historical cost less accumulated depreciation. The cost of these assets, less estimated residual value is depreciated on a straight-line basis over their estimated remaining economic useful lives. The estimated economic useful life of the Company's floaters, jack-up rigs and tender rigs, when new, is 30 years.

Significant investments are capitalized and depreciated in accordance with the nature of the investment. Significant investments that are deemed to increase an asset's value for its remaining useful life are capitalized and depreciated over the remaining life of the asset.

Assets are classified as held for sale when all of the following criteria are met, which are as follows: Management, having the authority to approve the action, commits to a plan to sell the asset (disposal group), the asset (disposal group) is available for immediate sale in its present condition subject only to terms that are usual and customary for sales of such assets (disposal groups), an active program to locate a buyer and other actions required to complete the plan to sell the asset (disposal group) have been initiated, the sale of the asset (disposal group) is probable, and transfer of the asset (disposal group) is expected to qualify for recognition as a completed sale, within one year. The term probable refers to a future sale that is likely to occur, the asset (disposal group) is being actively marketed for sale at a price that is reasonable in relation to its current fair value and actions required to complete the plan indicate that it is unlikely that significant changes to the plan will be made or that the plan will be withdrawn.

Cost of property and equipment sold or retired, with the related accumulated depreciation and write-downs are removed from the balance sheet, and resulting gains or losses are included in the consolidated statement of operations.

Equipment

Equipment is recorded at historical cost less accumulated depreciation and is depreciated over its estimated remaining useful life, which is between three and five years depending on the type of asset.

Goodwill

The Company allocates the purchase price of acquired businesses to the identifiable tangible and intangible assets and liabilities acquired, with any remaining amount being recorded as goodwill. Goodwill is tested for impairment at least annually at the reporting unit level, which is defined as an operating segment or a component of an operating segment that constitutes a business for which financial information is available and is regularly reviewed by management. The Company has determined that its reporting units are the same as its operating segments for the purpose of allocating goodwill and the subsequent testing of goodwill for impairment.

The Company first assesses qualitative factors to determine whether it is more likely than not that the fair value of a reporting unit is less than its carrying amount as a basis for determining whether it is necessary to perform the two step goodwill impairment test.

If the qualitative factors indicate possible impairment, the standard requires the Company to compare the fair value of its reporting units to their carrying value. In the event that the fair value is less than carrying value, the Company must perform an exercise similar to a purchase price allocation in a business combination in order to determine the amount of the impairment charge.

The goodwill impairment test for a reporting unit is based on discounted cash flows. The Company uses estimated future cash flows applying contract dayrates during the firm contract periods and estimated forecasted dayrates for the periods after expiry of firm contract periods. Zero escalation of dayrates for the periods will be assumed. The estimated future cash flows will be based on remaining economic useful lives for the assets, and discounted using a weighted average cost of capital (WACC).

Other intangible assets

Other intangible assets are recorded at historical cost less accumulated amortization. The cost of these assets less estimated residual value is amortized on a straight-line basis over the estimated remaining economic useful lives. Other intangible assets include technology and customer relationships.

Impairment of long-lived assets

The carrying value of long-lived assets that are held and used by the Company are reviewed for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may no longer be appropriate. The Company assesses recoverability of the carrying value of the asset by estimating the undiscounted future net cash flows expected to result from the asset, including eventual disposition. If the undiscounted future net cash flows are less than the carrying value of the asset, an impairment is made to the market value or the discounted future net cash flows.

Defined benefit pension plans

The Company has several defined benefit plans which provide retirement, death and early termination benefits. The Company's net obligation is calculated separately for each plan by estimating the amount of the future benefit that employees have earned in return for their cumulative service.

The aggregated projected future benefit obligation is discounted to a present value, and the aggregated fair value of any plan assets is deducted. The discount rate is the market yield at the balance sheet date on government bonds in the relevant currency and based on terms consistent with the post-employment benefit obligations. The retirement benefits are generally a function of number of years of employment and amount of employees' remuneration. The plans are primarily funded through payments to insurance companies. The Company records its pension costs in the period during which the services are rendered by the employees. Actuarial gains and losses are recognized in the statement of operations when the net cumulative unrecognized actuarial gains or losses for each individual plan at the end of the previous reporting year exceed 10 percent of the higher of the present value of the defined benefit obligation and the fair value of plan assets at that date. These gains and losses are recognized over the expected remaining working lives of the employees participating in the plans. Otherwise, recognition of actuarial gains and losses is included in other comprehensive income. Those amounts will be subsequently recognized as a component of net periodic pension cost on the same basis as the amounts recognized in accumulated other comprehensive income.

Treasury shares

Treasury shares are recognized at cost as a component of equity. The purchase of treasury shares reduces the Company's share capital by the nominal value of the acquired treasury shares. The amount paid in excess of the nominal value is treated as a reduction of additional paid-in capital.

Derivative Financial Instruments and Hedging Activities

The Company's interest-rate swap agreements, foreign currency options and forward exchange contracts are recorded at fair value. Changes in the fair value of interest-rate swap agreements, forward exchange and currency options contracts, which have not been designated as hedging instruments, are recorded as a gain or loss as a separate line item within Financial Items.

Changes in the fair value of any derivative instrument that we have formally designated as a hedge, are recognized in Accumulated other comprehensive income (loss) in the Consolidated Balance Sheets. Any change in fair value relating to an ineffective portion of a designated hedge is recognized, in the Consolidated Statement of Operations. When the hedged item affects the income statement, the gain or loss included in accumulated other comprehensive income is reported on the same line in the Consolidated Statements of Operations as the hedged item.

Financial instruments such as forward contracts to purchase shares that do not qualify as derivative instruments are not recognized on the balance sheet, unless deemed impaired. Such instruments are off-balance sheet transactions and result in only disclosures to the financial statements.

Income taxes

Seadrill is a Bermuda company. Currently, Seadrill is not required to pay taxes in Bermuda on ordinary income or capital gains as we qualify as an exempt company. The Company has received written assurance from the Minister of Finance in Bermuda that it will be exempt from taxation until March 2035. Certain subsidiaries operate in other jurisdictions where taxes are imposed. Consequently income taxes have been recorded in these jurisdictions when appropriate.

Significant judgment is involved in determining the provision for income taxes. There are certain transactions for which the ultimate tax determination is unclear due to uncertainty in the ordinary course of business. Seadrill recognizes tax liabilities based on its assessment of whether its tax positions are more likely than not sustainable, based on the technical merits and considerations of the relevant taxing authority's widely understood administrative practices and precedence.

Income tax expense consists of taxes currently payable and changes in deferred tax assets and liabilities calculated according to local tax rules. Deferred tax assets and liabilities are based on temporary differences that arise between carrying values used for financial reporting purposes and amounts used for taxation purposes of assets and liabilities and the future tax benefits of tax loss carry forwards. A deferred tax asset is recognized only to the extent that it is more likely than not that future taxable profits will be available against which the asset can be utilized. The amount of deferred tax provided is based upon the expected manner of settlement of the carrying amount of assets and liabilities, using tax rates enacted at the balance sheet date. The impact of tax law changes is recognized in periods when the change is enacted.

Deferred charges

Loan related costs, including debt arrangement fees, are capitalized and amortized over the term of the related loan and are included in interest expense.

Convertible debt

Convertible bond loans issued by the Company include both a loan component (host contract) and an option to convert the loan to shares (embedded derivative).

An embedded derivative, such as a conversion option, may be separated from its host contract and accounted for separately if certain criteria are met (including if the contract that embodies both the embedded derivative and the host contract is not measured at fair value, the economic characteristics and risks of the embedded derivative instrument are not clearly and closely related to the economic characteristics and risks of the host contract and if a separate instrument with the same terms as the embedded instrument would be a derivative).

If an embedded derivative instrument is separated from its host contract, the host contract shall be accounted for based on generally accepted accounting principles applicable to instruments of that type which do not contain embedded derivative instruments.

Total Return Equity Swaps

From time to time, the Company enters into total return equity swaps ("TRS") indexed to the Company's own shares, where the counterparty acquires shares in the Company and the Company carries the risk of fluctuations in the share price of the acquired shares. The fair value of each TRS is recorded as an asset or liability, with the changes in fair value recorded in the consolidated statement of operations. The Company may, from time to time, enter into TRS arrangements indexed to shares in other companies which are accounted for in a similar manner.

Share-based compensation

The Company has established an employee share ownership plan under which employees, directors and officers of the Group may be allocated options to subscribe for new shares in the ultimate parent, Seadrill Limited. The compensation cost for share options is recognized as an expense over the service period based on the fair value of the options granted.

The fair value of the share options issued under the Company's employee share option plans is determined at grant date taking into account the terms and conditions upon which the options are granted, and using a valuation technique that is consistent with generally accepted valuation methodologies for pricing financial instruments, and that incorporates all factors and assumptions that knowledgeable, willing market participants would consider in determining fair value. The fair value of the share options is recognized as personnel expenses with a corresponding increase in equity over the period during which the employees become unconditionally entitled to the options. Compensation cost is initially recognized based upon options expected to vest with appropriate adjustments to reflect actual forfeitures. National insurance contributions arising from such incentive programs are expensed when the options are exercised.

Provisions

A provision is recognized in the balance sheet when the Company has a present legal or constructive obligation as a result of a past event, and it is probable that an outflow of economic benefits will be required to settle the obligation and a reliable estimate of the amount can be made. If the effect is material, provisions are determined by discounting the expected future cash flows at a pre-tax rate that reflects current market assessments of the time value of money and, where appropriate, the risks specific to the liability.

Segment reporting

We have in 2011 and 2012 significantly expanded our fleet of drilling rigs through acquisitions of new rigs and newbuilding orders. In response to this development we reviewed our internal reporting structure including the operating and reporting business segments in 2011. The review resulted in a change in our reporting segments with effect from January 1, 2011.

As of December 31, 2012, the Company has three reportable business segments which include floaters, jack-up rigs and tender rigs. The well services business segment included the activities of Archer which performs various services related to platform drilling, drilling facility engineering, well intervention and oilfield services. With effect from the end of February 2011, Archer has been deconsolidated and the well services segment is no longer part of our consolidated financial statements.

Related parties

Parties are related if one party has the ability, directly or indirectly, to control the other party or exercise significant influence over the other party in making financial and operating decisions. Parties are also related if they are subject to common control or common significant influence. All transactions between the related parties are based on the principle of arm's length.

Earnings per share

Basic earnings per share ("EPS") is calculated based on the income (loss) for the period available to common stockholders divided by the weighted average number of shares outstanding for basic EPS for the period. Diluted EPS includes the effect of the assumed conversion of potentially dilutive instruments which for the Company includes share options and convertible debt. The determination of dilutive earnings per share requires the Company to potentially make certain adjustments to net income and for the weighted average shares outstanding used to compute basic earnings per share unless anti-dilutive.

Reclassifications

Certain reclassifications have been made to prior period amounts to conform to the current year presentation. These reclassifications did not have a material effect on the consolidated financial statements (refer to the Basis of preparation stated above).

Recently Issued Accounting Standards

Balance sheet—Effective January 1, 2013, we will adopt the accounting standards update that expands the disclosure requirements for the offsetting of assets and liabilities related to certain financial instruments and derivative instruments. The update requires disclosures to present both gross information and net information for financial instruments and derivative instruments that are eligible for net presentation due to a right of offset, an enforceable master netting arrangement or similar agreement. The update is effective for interim and annual periods beginning on or after January 1, 2013. We do not expect that our adoption will have a material effect on our consolidated balance sheet.

Balance sheet—Effective January 1, 2013, we will adopt the accounting standards update that requires an entity to report the effect of significant reclassifications out of accumulated other comprehensive income on the respective line items in net income if the amount being reclassified is required under U.S. generally accepted accounting principles (GAAP) to be reclassified in its entirety to net income. For other amounts that are not required under U.S. GAAP to be reclassified in their entirety to net income in the same reporting period, an entity is required to cross-reference other disclosures required under U.S. GAAP that provide additional detail about those amounts. For public entities, the amendments are effective prospectively for reporting periods beginning after December 15, 2012. We do not expect that our adoption will have a material effect on our financial statements.