XML 63 R42.htm IDEA: XBRL DOCUMENT
v3.6.0.2

Acquisitions, Divestitures, and Assets Held for Sale Divestitures and Assets Held for Sale (Details) $ in Thousands |  |  | 2 Months Ended | 12 Months Ended
--- | --- | --- | --- | ---
Feb. 23, 2017 USD ($) | Dec. 31, 2016 USD ($) MMBTU bbl | Feb. 15, 2017 USD ($) MMBTU $ / EnergyContent $ / Barrels bbl | Dec. 31, 2016 USD ($) | Dec. 31, 2015 USD ($) | Dec. 31, 2014 USD ($)
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] |  |  |  |  |  |  |
Proceeds from Sale of Oil and Gas Property and Equipment |  |  |  |  | $ 946,062 | $ 357,938 | $ 43,858
Net gain (loss) on divestiture activity |  |  |  |  | 37,074 | 43,031 | 646
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest |  |  |  |  | (1,201,916) | (722,861) | 1,064,699
Impairment of proved properties |  |  |  |  | $ 354,614 | 468,679 | 84,480
Assets Held-for-sale |  |  |  |  |  |  |
Reasonably certain period within which sale will take place (in years) |  |  |  |  | 1 year |  |
Oil and gas properties held for sale |  |  | $ 372,621 |  | $ 372,621 | 641 |
Asset Retirement Obligations Assets Held-for-sale Noncurrent |  |  | $ 26,241 |  | 26,241 | 241 |
Rocky Mountain Divestiture 2016 [Member] |  |  |  |  |  |  |
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] |  |  |  |  |  |  |
Proceeds from Sale of Oil and Gas Property and Equipment |  |  |  |  | 110,600 |  |
Net gain (loss) on divestiture activity |  |  |  |  | 16,400 |  |
Raven/Bear Den Divestiture 2016 [Member] |  |  |  |  |  |  |
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] |  |  |  |  |  |  |
Proceeds from Sale of Oil and Gas Property and Equipment |  |  |  |  | 756,200 |  |
Net gain (loss) on divestiture activity |  |  |  |  | 29,500 |  |
Permian Divestiture 2016 [Member] |  |  |  |  |  |  |
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] |  |  |  |  |  |  |
Proceeds from Sale of Oil and Gas Property and Equipment |  |  |  |  | 54,600 |  |
Net gain (loss) on divestiture activity |  |  |  |  | (10,100) |  |
Mid Continent Divestiture 2015 [Member] |  |  |  |  |  |  |
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] |  |  |  |  |  |  |
Proceeds from Sale of Oil and Gas Property and Equipment |  |  |  |  |  | 310,300 |
Net gain (loss) on divestiture activity |  |  |  |  |  | 108,400 |
Permian Divestiture 2015 [Member] |  |  |  |  |  |  |
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] |  |  |  |  |  |  |
Proceeds from Sale of Oil and Gas Property and Equipment |  |  |  |  |  | 25,100 |
Net gain (loss) on divestiture activity |  |  |  |  |  | 2,300 |
Other Divestitures 2015 [Member] |  |  |  |  |  |  |
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] |  |  |  |  |  |  |
Disposal Group, Not Discontinued Operation, Loss (Gain) on Write-down |  |  |  |  |  | 68,600 |
Rocky Mountain Divestiture 2014 [Member] |  |  |  |  |  |  |
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] |  |  |  |  |  |  |
Proceeds from Sale of Oil and Gas Property and Equipment |  |  |  |  |  |  | 42,000
Net gain (loss) on divestiture activity |  |  |  |  |  |  | 26,900
Other Divestitures 2014 [Member] |  |  |  |  |  |  |
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] |  |  |  |  |  |  |
Disposal Group, Not Discontinued Operation, Loss (Gain) on Write-down |  |  |  |  |  |  | 27,600
Disposal Group, Disposed of by Sale, Not Discontinued Operations [Member] | Raven/Bear Den Divestiture 2016 [Member] |  |  |  |  |  |  |
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] |  |  |  |  |  |  |
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest |  |  |  |  | (6,601) | (12,530) | 197,256
Impairment of proved properties |  |  |  |  |  | 17,800 |
Disposal Group, Held-for-sale, Not Discontinued Operations [Member] | Non-Operated Eagle Ford Divestiture 2017 [Member] |  |  |  |  |  |  |
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] |  |  |  |  |  |  |
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest |  |  |  |  | (218,506) | $ 71,556 | $ 294,376
Impairment of proved properties |  |  |  |  | $ 269,600 |  |
NYMEX Oil Swap Contracts [Member] |  |  |  |  |  |  |
Assets Held-for-sale |  |  |  |  |  |  |
Derivative, Nonmonetary Notional Amount, Volume | bbl |  |  | 5,612,000 |  |  |  |
Gas Swaps Contracts [Member] |  |  |  |  |  |  |
Assets Held-for-sale |  |  |  |  |  |  |
Derivative, Nonmonetary Notional Amount, Energy Measure | MMBTU | [1] |  | 192,192,000 |  |  |  |
Subsequent Event [Member] | Disposal Group, Held-for-sale, Not Discontinued Operations [Member] | Non-Operated Eagle Ford Divestiture 2017 [Member] |  |  |  |  |  |  |
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] |  |  |  |  |  |  |
Proceeds from Sale of Oil and Gas Property and Equipment |  |  |  | $ 800,000 |  |  |
Subsequent Event [Member] | NYMEX Oil Swap Contracts [Member] | Disposal Group, Held-for-sale, Not Discontinued Operations [Member] | Non-Operated Eagle Ford Divestiture 2017 [Member] |  |  |  |  |  |  |
Assets Held-for-sale |  |  |  |  |  |  |
Derivative, Nonmonetary Notional Amount, Volume | bbl |  |  |  | 4,300,000 |  |  |
Subsequent Event [Member] | Gas Swaps Contracts [Member] | Disposal Group, Held-for-sale, Not Discontinued Operations [Member] | Non-Operated Eagle Ford Divestiture 2017 [Member] |  |  |  |  |  |  |
Assets Held-for-sale |  |  |  |  |  |  |
Derivative, Nonmonetary Notional Amount, Energy Measure | MMBTU |  |  |  | 4,600,000 |  |  |
Subsequent Event [Member] | NGL Swaps Contracts [Member] |  |  |  |  |  |  |
Assets Held-for-sale |  |  |  |  |  |  |
Derivative, Nonmonetary Notional Amount, Volume | bbl |  |  |  | 1,100,000 |  |  |
Subsequent Event [Member] | NGL Swaps Contracts [Member] | Disposal Group, Held-for-sale, Not Discontinued Operations [Member] | Non-Operated Eagle Ford Divestiture 2017 [Member] |  |  |  |  |  |  |
Assets Held-for-sale |  |  |  |  |  |  |
Derivative, Nonmonetary Notional Amount, Volume | bbl |  |  |  | 4,500,000 |  |  |
Minimum [Member] | Subsequent Event [Member] | NYMEX Oil Swap Contracts [Member] | Disposal Group, Held-for-sale, Not Discontinued Operations [Member] | Non-Operated Eagle Ford Divestiture 2017 [Member] |  |  |  |  |  |  |
Assets Held-for-sale |  |  |  |  |  |  |
Derivative, Swap Type, Fixed Price | $ / Barrels |  |  |  | 54.05 |  |  |
Minimum [Member] | Subsequent Event [Member] | Gas Swaps Contracts [Member] | Disposal Group, Held-for-sale, Not Discontinued Operations [Member] | Non-Operated Eagle Ford Divestiture 2017 [Member] |  |  |  |  |  |  |
Assets Held-for-sale |  |  |  |  |  |  |
Derivative, Swap Type, Fixed Price | $ / EnergyContent |  |  |  | 2.82 |  |  |
Minimum [Member] | Subsequent Event [Member] | NGL Swaps Contracts [Member] |  |  |  |  |  |  |
Assets Held-for-sale |  |  |  |  |  |  |
Derivative, Swap Type, Fixed Price | $ / Barrels |  |  |  | 35.07 |  |  |
Minimum [Member] | Subsequent Event [Member] | NGL Swaps Contracts [Member] | Disposal Group, Held-for-sale, Not Discontinued Operations [Member] | Non-Operated Eagle Ford Divestiture 2017 [Member] |  |  |  |  |  |  |
Assets Held-for-sale |  |  |  |  |  |  |
Derivative, Swap Type, Fixed Price | $ / Barrels |  |  |  | 11.81 |  |  |
Maximum [Member] | Subsequent Event [Member] | NYMEX Oil Swap Contracts [Member] | Disposal Group, Held-for-sale, Not Discontinued Operations [Member] | Non-Operated Eagle Ford Divestiture 2017 [Member] |  |  |  |  |  |  |
Assets Held-for-sale |  |  |  |  |  |  |
Derivative, Swap Type, Fixed Price | $ / Barrels |  |  |  | 57.00 |  |  |
Maximum [Member] | Subsequent Event [Member] | Gas Swaps Contracts [Member] | Disposal Group, Held-for-sale, Not Discontinued Operations [Member] | Non-Operated Eagle Ford Divestiture 2017 [Member] |  |  |  |  |  |  |
Assets Held-for-sale |  |  |  |  |  |  |
Derivative, Swap Type, Fixed Price | $ / EnergyContent |  |  |  | 2.99 |  |  |
Maximum [Member] | Subsequent Event [Member] | NGL Swaps Contracts [Member] |  |  |  |  |  |  |
Assets Held-for-sale |  |  |  |  |  |  |
Derivative, Swap Type, Fixed Price | $ / Barrels |  |  |  | 49.88 |  |  |
Maximum [Member] | Subsequent Event [Member] | NGL Swaps Contracts [Member] | Disposal Group, Held-for-sale, Not Discontinued Operations [Member] | Non-Operated Eagle Ford Divestiture 2017 [Member] |  |  |  |  |  |  |
Assets Held-for-sale |  |  |  |  |  |  |
Derivative, Swap Type, Fixed Price | $ / Barrels |  |  |  | 48.51 |  |  |
Scenario, Forecast [Member] | Minimum [Member] | Subsequent Event [Member] | Disposal Group, Held-for-sale, Not Discontinued Operations [Member] | Divide County Divestiture 2017 [Member] |  |  |  |  |  |  |
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] |  |  |  |  |  |  |
Disposal Group, Not Discontinued Operation, Loss (Gain) on Write-down |  | $ 200,000 |  |  |  |  |
Scenario, Forecast [Member] | Maximum [Member] | Subsequent Event [Member] | Disposal Group, Held-for-sale, Not Discontinued Operations [Member] | Divide County Divestiture 2017 [Member] |  |  |  |  |  |  |
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] |  |  |  |  |  |  |
Disposal Group, Not Discontinued Operation, Loss (Gain) on Write-down |  | $ 400,000 |  |  |  |  |
[1] | Total net volumes of natural gas swaps are comprised of IF El Paso Permian (3%), IF HSC (94%), and IF NNG Ventura (3%).

X
- Definition Noncurrent portion of the carrying amount of a liability for an asset retirement obligation for an asset held for sale. An asset retirement obligation is a legal obligation associated with the disposal or retirement of a tangible long-lived asset that results from the acquisition, construction or development, or the normal operations of a long-lived asset, except for certain obligations of lessees. + References No definition available. + Details
Name: | sm_AssetRetirementObligationsAssetsHeldForSaleNoncurrent
Namespace Prefix: | sm_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Represents the period where there is reasonable certainty that the sale will take place for the assets to be classified as held for sale. + References No definition available. + Details
Name: | sm_AssetsHeldforsaleReasonablyCertainPeriodforSale
Namespace Prefix: | sm_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Assets Held for Sale + References No definition available. + Details
Name: | sm_AssetsheldforsaleAbstract
Namespace Prefix: | sm_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition The impairment expense recorded to reduce the value of proved oil and gas assets. + References No definition available. + Details
Name: | sm_ImpairmentofProvedOilandGasProperties
Namespace Prefix: | sm_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amount classified as assets attributable to disposal group held for sale or disposed of, expected to be disposed of within one year or the normal operating cycle, if longer. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 205 -SubTopic 20 -Section 45 -Paragraph 10 -URI http://asc.fasb.org/extlink&oid=65878427&loc=d3e1107-107759 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 205 -SubTopic 20 -Section 45 -Paragraph 11 -URI http://asc.fasb.org/extlink&oid=65878427&loc=SL51721533-107759 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 360 -SubTopic 10 -Section 50 -Paragraph 3 -Subparagraph (e) -URI http://asc.fasb.org/extlink&oid=64862545&loc=d3e2941-110230 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 205 -SubTopic 20 -Section 50 -Paragraph 5B -Subparagraph (e) -URI http://asc.fasb.org/extlink&oid=64827811&loc=SL51721673-107760 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 360 -SubTopic 10 -Section 45 -Paragraph 9 -URI http://asc.fasb.org/extlink&oid=68055307&loc=d3e2473-110228 + Details
Name: | us-gaap_AssetsOfDisposalGroupIncludingDiscontinuedOperationCurrent
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Nominal energy measure used to calculate payments on a derivative instrument. + References No definition available. + Details
Name: | us-gaap_DerivativeNonmonetaryNotionalAmountEnergyMeasure
Namespace Prefix: | us-gaap_
Data Type: | num:energyItemType
Balance Type: | na
Period Type: | duration

X
- Definition Nominal volume used to calculate payments on a derivative instrument. + References No definition available. + Details
Name: | us-gaap_DerivativeNonmonetaryNotionalAmountVolume
Namespace Prefix: | us-gaap_
Data Type: | num:volumeItemType
Balance Type: | na
Period Type: | duration

X
- Definition Fixed price related to the price risk swap derivative. + References No definition available. + Details
Name: | us-gaap_DerivativeSwapTypeFixedPrice
Namespace Prefix: | us-gaap_
Data Type: | us-types:perUnitItemType
Balance Type: | na
Period Type: | instant

X
- Definition Amount, before tax, of (gain) loss recognized for the (reversal of write-down) write-down to fair value, less cost to sell, of a disposal group. Excludes discontinued operations. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 360 -SubTopic 10 -Section 50 -Paragraph 3 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=64862545&loc=d3e2941-110230 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 360 -SubTopic 10 -Section 45 -Paragraph 5 -URI http://asc.fasb.org/extlink&oid=68055307&loc=d3e2443-110228 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=66902209&loc=d3e3602-108585 + Details
Name: | us-gaap_DisposalGroupNotDiscontinuedOperationLossGainOnWriteDown
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amount of gain (loss) on sale or disposal of proven and unproven oil and gas properties. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=66902209&loc=d3e3602-108585 + Details
Name: | us-gaap_GainLossOnSaleOfOilAndGasProperty
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Amount of income (loss) from continuing operations, including income (loss) from equity method investments, before deduction of income tax expense (benefit), and income (loss) attributable to noncontrolling interest. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 940 -SubTopic 20 -Section 25 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=68072869&loc=d3e41242-110953 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 225 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SX 210.5-03(10)) -URI http://asc.fasb.org/extlink&oid=63488584&loc=d3e20235-122688 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 225 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-04(15)) -URI http://asc.fasb.org/extlink&oid=6879574&loc=d3e536633-122882 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 225 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-04(8)) -URI http://asc.fasb.org/extlink&oid=6879464&loc=d3e573970-122913 + Details
Name: | us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
Name: | us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition The cash inflow to dispose of long-lived, physical assets and mineral interests in oil and gas properties used for normal oil and gas operations. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Investing Activities -URI http://asc.fasb.org/extlink&oid=6516133 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 12 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=66902209&loc=d3e3179-108585 + Details
Name: | us-gaap_ProceedsFromSaleOfOilAndGasPropertyAndEquipment
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Details
Name: | us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis=sm_RockyMountainDivestiture2016Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis=sm_RavenBearDenDivestiture2016Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis=sm_PermianDivestiture2016Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis=sm_MidContinentDivestiture2015Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis=sm_PermianDivestiture2015Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis=sm_OtherDivestitures2015Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis=sm_RockyMountainDivestiture2014Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis=sm_OtherDivestitures2014Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DisposalGroupClassificationAxis=us-gaap_DisposalGroupDisposedOfBySaleNotDiscontinuedOperationsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DisposalGroupClassificationAxis=us-gaap_DisposalGroupHeldforsaleNotDiscontinuedOperationsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis=sm_NonOperatedEagleFordDivestiture2017Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DerivativeInstrumentRiskAxis=sm_NYMEXOilSwapContractsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DerivativeInstrumentRiskAxis=sm_GasSwapsContractsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_SubsequentEventTypeAxis=us-gaap_SubsequentEventMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DerivativeInstrumentRiskAxis=sm_NGLSwapsContractsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RangeAxis=us-gaap_MinimumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RangeAxis=us-gaap_MaximumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementScenarioAxis=us-gaap_ScenarioForecastMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis=sm_DivideCountyDivestiture2017Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |