Significant Accounting Policies (Policies)	9 Months Ended
Sep. 30, 2018
Significant Accounting Policies
Presentation	Presentation—We have prepared our accompanying unaudited condensed consolidated financial statements in accordance with accounting principles generally accepted in the United States (“U.S.”) for interim financial information and with the instructions to Form 10‑Q and Article 10 of Regulation S‑X of the U.S. Securities and Exchange Commission. Pursuant to such rules and regulations, these financial statements do not include all disclosures required by accounting principles generally accepted in the U.S. for complete financial statements. The condensed consolidated financial statements reflect all adjustments, which are, in the opinion of management, necessary for a fair presentation of financial position, results of operations and cash flows for the interim periods. Such adjustments are considered to be of a normal recurring nature unless otherwise noted. Operating results for the three and nine months ended September 30, 2018, are not necessarily indicative of the results that may be expected for the year ending December 31, 2018, or for any future period. The accompanying condensed consolidated financial statements and notes thereto should be read in conjunction with the audited consolidated financial statements and notes thereto as of December 31, 2017 and 2016, and for each of the three years in the period ended December 31, 2017, included in our annual report on Form 10‑K filed on February 21, 2018.
Accounting estimates	Accounting estimates—To prepare financial statements in accordance with accounting principles generally accepted in the U.S., we are required to make estimates and assumptions that affect the reported amounts of assets, liabilities, revenues and expenses and the disclosures of contingent assets and liabilities. On an ongoing basis, we evaluate our estimates and assumptions, including those related to our allowance for doubtful accounts, materials and supplies obsolescence, property and equipment, assets held for sale, goodwill, income taxes, contingencies, share‑based compensation and postemployment benefit plans. We base our estimates and assumptions on historical experience and on various other factors we believe are reasonable under the circumstances, the results of which form the basis for making judgments about the carrying amounts of assets and liabilities that are not readily apparent from other sources. Actual results could differ from such estimates.
Fair value measurements	Fair value measurements—We estimate fair value at a price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants in the principal market for the asset or liability. Our valuation techniques require inputs that we categorize using a three‑level hierarchy, from highest to lowest level of observable inputs, as follows: (1) significant observable inputs, including unadjusted quoted prices for identical assets or liabilities in active markets (“Level 1”), (2) significant other observable inputs, including direct or indirect market data for similar assets or liabilities in active markets or identical assets or liabilities in less active markets (“Level 2”) and (3) significant unobservable inputs, including those that require considerable judgment for which there is little or no market data (“Level 3”). When multiple input levels are required for a valuation, we categorize the entire fair value measurement according to the lowest level of input that is significant to the measurement even though we may have also utilized significant inputs that are more readily observable.
Business combination	Business combination—In connection with the Songa acquisition, we applied the acquisition method of accounting. Accordingly, we recorded the acquired assets and assumed liabilities at fair value and recognized goodwill to the extent the consideration transferred exceeded the fair value of the net assets acquired. We estimated the fair values of the acquired assets and assumed liabilities as of the date of the acquisition, and our estimates are subject to adjustment based on our final assessments of the fair values of property and equipment, intangible assets, other assets and liabilities and our evaluation of tax positions and contingencies, which are ongoing. We will complete our final assessments of the fair values of the acquired assets and assumed liabilities and our final evaluations of uncertain tax positions and contingencies within one year of the acquisition date. See Note 4—Business Combinations.
Goodwill	Goodwill—We conduct impairment testing for our goodwill annually as of October 1 and more frequently, on an interim basis, when an event occurs or circumstances change that indicate that the fair value of our reporting unit may have declined below its carrying value. We test goodwill at the reporting unit level, which is defined as an operating segment or one level below an operating segment that constitutes a business for which financial information is available and is regularly reviewed by management. We determined that we have a single reporting unit for this purpose. Before testing goodwill, we consider whether or not to first assess qualitative factors to determine whether the existence of events or circumstances leads to a determination that it is more likely than not that the fair value of a reporting unit is less than its carrying amount. If, as the result of our qualitative assessment, we determine that an impairment test is required, or, alternatively, if we elect to forgo the qualitative assessment, we record an impairment to goodwill to the extent the carrying amount of the reporting unit, including goodwill, exceeds the fair value of the reporting unit. In the nine months ended September 30, 2018, as a result of an interim goodwill test, we recognized an aggregate loss of $462 million, which had no tax effect, associated with the impairment of our goodwill. See Note 3—Accounting Standards Updates, Note 4—Business Combinations and Note 7—Goodwill.
Contract intangible assets	Contract intangible assets—In connection with the Songa acquisition, we recognized drilling contract intangible assets related to the acquired drilling contracts for future contract drilling services. The drilling contract intangible assets represent the amount by which the fixed dayrates of the acquired contracts were above the market dayrates that were available or expected to be available during the term of the contract for similar contracts, measured as of the acquisition date. We recognize the amortization on a straight‑line basis over the firm contract period as a reduction of contract drilling revenues. At September 30, 2018, the carrying amount of our drilling contract intangible assets was $554 million. See Note 4—Business Combinations.
Derivative instruments	Derivative instruments—We record derivatives on our consolidated balance sheet, measured at fair value. We recognize the gains and losses associated with changes in the fair value of undesignated derivatives in current period earnings. See Note 9—Derivative Instruments.
Capitalized interest	Capitalized interest—We capitalize interest costs for qualifying construction and upgrade projects and only capitalize interest costs during periods in which progress for the construction projects continues to be underway. In the three and nine months ended September 30, 2018, we capitalized interest costs of $8 million and $28 million, respectively, for our construction work in progress. In the three and nine months ended September 30, 2017, we capitalized interest costs of $31 million and $91 million, respectively, for our construction work in progress.
Reclassifications	Reclassifications—We have made certain reclassifications to prior period amounts to conform with the current period’s presentation. In our condensed consolidated balance sheet as of December 31, 2017, we reclassified certain balances receivable from non‑customers, totaling $45 million, from accounts receivable, net, to other current assets. Such reclassifications did not have a material effect on our condensed consolidated statement of financial position, results of operations or cash flows.

Significant Accounting Policies (Policies)

9 Months Ended

Sep. 30, 2018

Presentation—We have prepared our accompanying unaudited condensed consolidated financial statements in accordance with accounting principles generally accepted in the United States (“U.S.”) for interim financial information and with the instructions to Form 10‑Q and Article 10 of Regulation S‑X of the U.S. Securities and Exchange Commission. Pursuant to such rules and regulations, these financial statements do not include all disclosures required by accounting principles generally accepted in the U.S. for complete financial statements. The condensed consolidated financial statements reflect all adjustments, which are, in the opinion of management, necessary for a fair presentation of financial position, results of operations and cash flows for the interim periods. Such adjustments are considered to be of a normal recurring nature unless otherwise noted. Operating results for the three and nine months ended September 30, 2018, are not necessarily indicative of the results that may be expected for the year ending December 31, 2018, or for any future period. The accompanying condensed consolidated financial statements and notes thereto should be read in conjunction with the audited consolidated financial statements and notes thereto as of December 31, 2017 and 2016, and for each of the three years in the period ended December 31, 2017, included in our annual report on Form 10‑K filed on February 21, 2018.

Accounting estimates

Accounting estimates—To prepare financial statements in accordance with accounting principles generally accepted in the U.S., we are required to make estimates and assumptions that affect the reported amounts of assets, liabilities, revenues and expenses and the disclosures of contingent assets and liabilities. On an ongoing basis, we evaluate our estimates and assumptions, including those related to our allowance for doubtful accounts, materials and supplies obsolescence, property and equipment, assets held for sale, goodwill, income taxes, contingencies, share‑based compensation and postemployment benefit plans. We base our estimates and assumptions on historical experience and on various other factors we believe are reasonable under the circumstances, the results of which form the basis for making judgments about the carrying amounts of assets and liabilities that are not readily apparent from other sources. Actual results could differ from such estimates.

Fair value measurements

Fair value measurements—We estimate fair value at a price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants in the principal market for the asset or liability. Our valuation techniques require inputs that we categorize using a three‑level hierarchy, from highest to lowest level of observable inputs, as follows: (1) significant observable inputs, including unadjusted quoted prices for identical assets or liabilities in active markets (“Level 1”), (2) significant other observable inputs, including direct or indirect market data for similar assets or liabilities in active markets or identical assets or liabilities in less active markets (“Level 2”) and (3) significant unobservable inputs, including those that require considerable judgment for which there is little or no market data (“Level 3”). When multiple input levels are required for a valuation, we categorize the entire fair value measurement according to the lowest level of input that is significant to the measurement even though we may have also utilized significant inputs that are more readily observable.

Business combination

Business combination—In connection with the Songa acquisition, we applied the acquisition method of accounting. Accordingly, we recorded the acquired assets and assumed liabilities at fair value and recognized goodwill to the extent the consideration transferred exceeded the fair value of the net assets acquired. We estimated the fair values of the acquired assets and assumed liabilities as of the date of the acquisition, and our estimates are subject to adjustment based on our final assessments of the fair values of property and equipment, intangible assets, other assets and liabilities and our evaluation of tax positions and contingencies, which are ongoing. We will complete our final assessments of the fair values of the acquired assets and assumed liabilities and our final evaluations of uncertain tax positions and contingencies within one year of the acquisition date. See Note 4—Business Combinations.

Goodwill

Goodwill—We conduct impairment testing for our goodwill annually as of October 1 and more frequently, on an interim basis, when an event occurs or circumstances change that indicate that the fair value of our reporting unit may have declined below its carrying value. We test goodwill at the reporting unit level, which is defined as an operating segment or one level below an operating segment that constitutes a business for which financial information is available and is regularly reviewed by management. We determined that we have a single reporting unit for this purpose. Before testing goodwill, we consider whether or not to first assess qualitative factors to determine whether the existence of events or circumstances leads to a determination that it is more likely than not that the fair value of a reporting unit is less than its carrying amount. If, as the result of our qualitative assessment, we determine that an impairment test is required, or, alternatively, if we elect to forgo the qualitative assessment, we record an impairment to goodwill to the extent the carrying amount of the reporting unit, including goodwill, exceeds the fair value of the reporting unit. In the nine months ended September 30, 2018, as a result of an interim goodwill test, we recognized an aggregate loss of $462 million, which had no tax effect, associated with the impairment of our goodwill. See Note 3—Accounting Standards Updates, Note 4—Business Combinations and Note 7—Goodwill.

Contract intangible assets

Contract intangible assets—In connection with the Songa acquisition, we recognized drilling contract intangible assets related to the acquired drilling contracts for future contract drilling services. The drilling contract intangible assets represent the amount by which the fixed dayrates of the acquired contracts were above the market dayrates that were available or expected to be available during the term of the contract for similar contracts, measured as of the acquisition date. We recognize the amortization on a straight‑line basis over the firm contract period as a reduction of contract drilling revenues. At September 30, 2018, the carrying amount of our drilling contract intangible assets was $554 million. See Note 4—Business Combinations.

Derivative instruments

Derivative instruments—We record derivatives on our consolidated balance sheet, measured at fair value. We recognize the gains and losses associated with changes in the fair value of undesignated derivatives in current period earnings. See Note 9—Derivative Instruments.

Capitalized interest

Capitalized interest—We capitalize interest costs for qualifying construction and upgrade projects and only capitalize interest costs during periods in which progress for the construction projects continues to be underway. In the three and nine months ended September 30, 2018, we capitalized interest costs of $8 million and $28 million, respectively, for our construction work in progress. In the three and nine months ended September 30, 2017, we capitalized interest costs of $31 million and $91 million, respectively, for our construction work in progress.

Reclassifications

Reclassifications—We have made certain reclassifications to prior period amounts to conform with the current period’s presentation. In our condensed consolidated balance sheet as of December 31, 2017, we reclassified certain balances receivable from non‑customers, totaling $45 million, from accounts receivable, net, to other current assets. Such reclassifications did not have a material effect on our condensed consolidated statement of financial position, results of operations or cash flows.