Supplemental Oil and Gas Disclosures - Capitalized Costs Related to Oil and Natural Gas (Details) - USD ($) $ in Millions |
Dec. 31, 2017 |
Dec. 31, 2016 |
Dec. 31, 2015 |
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| Net capitalized cost: | |||||
| Proved oil and natural gas properties and equipment | $ 8,102.0 | $ 7,932.5 | $ 7,882.3 | ||
| Unproved oil and natural gas properties and equipment | 20.2 | ||||
| Accumulated depreciation, depletion and amortization related to oil, NGLs and natural gas activities | [1] | (7,525.0) | (7,387.8) | (6,916.2) | |
| Net capitalized costs related to producing activities | $ 577.0 | $ 544.7 | $ 986.3 | ||
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- Definition Amount of accumulated depreciation, depletion, amortization and valuation allowance relating to oil and gas producing activities. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition Capitalized costs of proved properties that include fee ownership or a lease, concession, or other interest representing the right to extract oil or gas subject to such terms as may be imposed by the conveyance of that interest. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition Capitalized costs of unproven properties that include fee ownership or a lease, concession, or other interest representing the right to extract oil or gas subject to such terms as may be imposed by the conveyance of that interest. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition Net amount of capitalized costs relating to oil and gas producing activities. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- References No definition available.
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