| Acquisitions and Divestitures - Additional Information (Details) - USD ($) $ in Millions | Sep. 28, 2018 | Apr. 05, 2018 | 
|---|---|---|
| Heidelberg Field Acquisition | ||
| Business Acquisition [Line Items] | ||
| Gross purchase price | $ 31.1 | |
| Net purchase price | 16.8 | |
| Letters of credit outstanding | 9.4 | |
| Asset retirement obligations recognized | $ 3.6 | |
| Purchase obligations due, year | 2028 | |
| Purchase commitment | $ 19.6 | |
| Permian Basin | ||
| Business Acquisition [Line Items] | ||
| Net proceeds received from divestiture | $ 56.6 | |
| Cobalt International Energy, Inc | Heidelberg Field Acquisition | ||
| Business Acquisition [Line Items] | ||
| Percentage of non-operated working interest acquired | 9.375% | 
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- Definition The total amount of the contingent obligation under letters of credit outstanding as of the reporting date. No definition available. 
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- Definition The cash outflow associated with the acquisition of business during the period. The cash portion only of the acquisition price. Reference 1: http://www.xbrl.org/2003/role/disclosureRef 
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- Definition The cash inflow from the sale of property, plant and equipment (capital expenditures), software, and other intangible assets. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef 
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- Definition Minimum amount of purchase arrangement in which the entity has agreed to expend funds to procure goods or services from a supplier. No definition available. 
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