Basis of Presentation	3 Months Ended
Mar. 31, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Presentation	Basis of Presentation Presentation. In the opinion of management, the unaudited interim consolidated financial statements of the Company as of March 31, 2019 and for the three months ended March 31, 2019 and 2018 include all adjustments and accruals, consisting only of normal, recurring adjustments and accruals necessary for a fair presentation of the results for the interim periods in conformity with generally accepted accounting principles in the United States ("GAAP"). The operating results for the three months ended March 31, 2019 are not necessarily indicative of the results to be expected for the full year. Certain information and footnote disclosures normally included in financial statements prepared in accordance with GAAP have been condensed or omitted in accordance with the rules and regulations of the United States Securities and Exchange Commission (the "SEC"). These unaudited interim consolidated financial statements should be read together with the consolidated financial statements and notes thereto included in the Company's Annual Report on Form 10-K for the year ended December 31, 2018. Certain reclassifications have been made to prior period amounts to conform to the current period's presentation. Use of estimates in the preparation of financial statements. Preparation of the Company's unaudited interim consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting periods. Depletion of oil and gas properties and impairment of goodwill and proved and unproved oil and gas properties, in part, is determined using estimates of proved, probable and possible oil and gas reserves. There are numerous uncertainties inherent in the estimation of quantities of proved, probable and possible reserves and in the projection of future rates of production and the timing of development expenditures. Similarly, evaluations for impairment of proved and unproved oil and gas properties are subject to numerous uncertainties including, among others, estimates of future recoverable reserves and commodity price outlooks. Actual results could differ from the estimates and assumptions utilized. Adoption of new accounting standards. In February 2016, the Financial Accounting Standards Board ("FASB") issued Accounting Standards Update ("ASU") 2016-02, "Leases (Topic 842)" ("ASC 842") which supersedes the lease recognition requirements in Accounting Standards Codification ("ASC") 840, "Leases" ("ASC 840"), and requires lessees to recognize lease assets and lease liabilities for those leases previously classified as operating leases. The Company adopted ASC 842 as of January 1, 2019 using the modified retrospective transition method. The Company elected to apply the transition guidance under ASU 2018-11, "Leases (Topic 842) Targeted Improvements," in which ASC 842 is applied at the adoption date, while the comparative periods continue to be reported in accordance with historic accounting under ASC 840. This standard does not apply to leases to explore for or use minerals, oil or gas resources, including the right to explore for those natural resources and rights to use the land in which those natural resources are contained. ASC 842 allowed for the election of certain practical expedients at adoption to ease the burden of implementation. At implementation, the Company elected to (i) maintain the historical lease classification for leases prior to January 1, 2019, (ii) maintain the historical accounting treatment for land easements that existed at adoption, (iii) use historical practices in assessing the lease term of existing contracts at adoption, (iv) combine lease and non-lease components of a contract as a single lease and (v) not record short-term leases on the consolidated balance sheet, all in accordance with ASC 842. As of March 31, 2019, the Company's operating lease assets and liabilities totaled $356 million and $362 million, respectively, on the consolidated balance sheet, in accordance with ASC 842. The adoption of ASC 842 did not have a material impact on the consolidated statements of operations and had no impact on cash flows. The Company did not record a change to its opening retained earnings as of January 1, 2019, as there was no material change to the timing or pattern of recognition of lease costs due to the adoption of ASC 842. As of December 31, 2018, the Company was the deemed owner of the Company's new corporate headquarters (for accounting purposes) during the construction period and was following the build-to-suit accounting guidance under ASC 840. On January 1, 2019, upon the adoption of ASC 842, the Company derecognized $217 million of other property and equipment and $219 million of build-to-suit lease liability costs associated with the building as this contract no longer qualifies for capitalization. The contract will be evaluated and recorded on the Company's consolidated balance sheets upon lease commencement, which is expected to occur during the second half of 2019. See Note 10 for additional information. New accounting pronouncements. In June 2016, the FASB issued ASU 2016-13, "Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments" (ASU 2016-13). ASU 2016-13 changes the impairment model for most financial assets and certain other instruments, including trade and other receivables, and requires entities to use a new forward-looking expected loss model that will result in the earlier recognition of allowances for losses. This update is effective for fiscal years beginning after December 15, 2019, including interim periods within those fiscal years, with early adoption permitted. Entities will use the modified retrospective approach to apply the standard's provisions and record a cumulative-effect adjustment to retained earnings as of the beginning of the first reporting period in which the guidance is adopted. The Company continues to evaluate ASU 2016-13 but does not expect that it will have a material impact on its consolidated financial statements.

Basis of Presentation

Presentation. In the opinion of management, the unaudited interim consolidated financial statements of the Company as of March 31, 2019 and for the three months ended March 31, 2019 and 2018 include all adjustments and accruals, consisting only of normal, recurring adjustments and accruals necessary for a fair presentation of the results for the interim periods in conformity with generally accepted accounting principles in the United States ("GAAP"). The operating results for the three months ended March 31, 2019 are not necessarily indicative of the results to be expected for the full year.

Certain information and footnote disclosures normally included in financial statements prepared in accordance with GAAP have been condensed or omitted in accordance with the rules and regulations of the United States Securities and Exchange Commission (the "SEC"). These unaudited interim consolidated financial statements should be read together with the consolidated financial statements and notes thereto included in the Company's Annual Report on Form 10-K for the year ended December 31, 2018.

Certain reclassifications have been made to prior period amounts to conform to the current period's presentation.

Use of estimates in the preparation of financial statements. Preparation of the Company's unaudited interim consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting periods. Depletion of oil and gas properties and impairment of goodwill and proved and unproved oil and gas properties, in part, is determined using estimates of proved, probable and possible oil and gas reserves. There are numerous uncertainties inherent in the estimation of quantities of proved, probable and possible reserves and in the projection of future rates of production and the timing of development expenditures. Similarly, evaluations for impairment of proved and unproved oil and gas properties are subject to numerous uncertainties including, among others, estimates of future recoverable reserves and commodity price outlooks. Actual results could differ from the estimates and assumptions utilized.

Adoption of new accounting standards. In February 2016, the Financial Accounting Standards Board ("FASB") issued Accounting Standards Update ("ASU") 2016-02, "Leases (Topic 842)" ("ASC 842") which supersedes the lease recognition requirements in Accounting Standards Codification ("ASC") 840, "Leases" ("ASC 840"), and requires lessees to recognize lease assets and lease liabilities for those leases previously classified as operating leases. The Company adopted ASC 842 as of January 1, 2019 using the modified retrospective transition method. The Company elected to apply the transition guidance under ASU 2018-11, "Leases (Topic 842) Targeted Improvements," in which ASC 842 is applied at the adoption date, while the comparative periods continue to be reported in accordance with historic accounting under ASC 840. This standard does not apply to leases to explore for or use minerals, oil or gas resources, including the right to explore for those natural resources and rights to use the land in which those natural resources are contained.

ASC 842 allowed for the election of certain practical expedients at adoption to ease the burden of implementation. At implementation, the Company elected to (i) maintain the historical lease classification for leases prior to January 1, 2019, (ii) maintain the historical accounting treatment for land easements that existed at adoption, (iii) use historical practices in assessing the lease term of existing contracts at adoption, (iv) combine lease and non-lease components of a contract as a single lease and (v) not record short-term leases on the consolidated balance sheet, all in accordance with ASC 842.

As of March 31, 2019, the Company's operating lease assets and liabilities totaled $356 million and $362 million, respectively, on the consolidated balance sheet, in accordance with ASC 842. The adoption of ASC 842 did not have a material impact on the consolidated statements of operations and had no impact on cash flows. The Company did not record a change to its opening retained earnings as of January 1, 2019, as there was no material change to the timing or pattern of recognition of lease costs due to the adoption of ASC 842.

As of December 31, 2018, the Company was the deemed owner of the Company's new corporate headquarters (for accounting purposes) during the construction period and was following the build-to-suit accounting guidance under ASC 840. On January 1, 2019, upon the adoption of ASC 842, the Company derecognized $217 million of other property and equipment and $219 million of build-to-suit lease liability costs associated with the building as this contract no longer qualifies for capitalization. The contract will be evaluated and recorded on the Company's consolidated balance sheets upon lease commencement, which is expected to occur during the second half of 2019.

See Note 10 for additional information.

New accounting pronouncements. In June 2016, the FASB issued ASU 2016-13, "Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments" (ASU 2016-13). ASU 2016-13 changes the impairment model for most financial assets and certain other instruments, including trade and other receivables, and requires entities to use a new forward-looking expected loss model that will result in the earlier recognition of allowances for losses. This update is effective for fiscal years beginning after December 15, 2019, including interim periods within those fiscal years, with early adoption permitted. Entities will use the modified retrospective approach to apply the standard's provisions and record a cumulative-effect adjustment to retained earnings as of the beginning of the first reporting period in which the guidance is adopted. The Company continues to evaluate ASU 2016-13 but does not expect that it will have a material impact on its consolidated financial statements.