Contractual Obligation on Non-Operated Eagle Ford Assets

No definition available.

Name:	sm_ContractualObligationNonOperatedEagleFordAssets
Namespace Prefix:	sm_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Early Termination Penalty for Rig Contract Cancellation

+ References

No definition available.

+ Details

Name:	sm_EarlyTerminationPenaltyforRigContractCancellation
Namespace Prefix:	sm_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Oil and Gas Delivery Commitments and Contracts, Remaining Contractual Volume on Non-Operated Eagle Ford Assets

+ References

No definition available.

+ Details

Name:	sm_OilandGasDeliveryCommitmentsandContractsRemainingContractualVolumeonNonOperatedEagleFordAssets
Namespace Prefix:	sm_
Data Type:	num:volumeItemType
Balance Type:	na
Period Type:	instant

- Definition

Total amount of water committed to be supplied under existing contracts or agreements.

+ References

No definition available.

+ Details

Name:	sm_WaterDeliveryCommitmentsandContractsRemainingContractualVolume
Namespace Prefix:	sm_
Data Type:	num:volumeItemType
Balance Type:	na
Period Type:	instant

- Definition

Amount of contractual obligation, including but not limited to, long-term debt, capital lease obligations, operating lease obligations, purchase obligations, and other commitments.

+ References

No definition available.

+ Details

Name:	us-gaap_ContractualObligation
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Volume that must be purchased within the specified time period of the agreement to avoid penalties or unfavorable effects on pricing, among other adverse consequences.

+ References

No definition available.

+ Details

Name:	us-gaap_LongTermPurchaseCommitmentMinimumVolumeRequired
Namespace Prefix:	us-gaap_
Data Type:	num:volumeItemType
Balance Type:	na
Period Type:	duration

- Definition

Total amount of product committed to be supplied under existing contracts or agreements.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-K (SK)
-Number 229
-Section 1207
-Paragraph (a)
-Subparagraph (2)

+ Details

Name:	us-gaap_OilAndGasDeliveryCommitmentsAndContractsRemainingContractualVolume
Namespace Prefix:	us-gaap_
Data Type:	num:volumeItemType
Balance Type:	na
Period Type:	instant

- 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_OtherCommitmentsLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_OtherCommitmentsAxis=sm_PipelineCommitmentsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_OtherCommitmentsAxis=sm_WaterPipelineCommitmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_OtherCommitmentsAxis=sm_WaterPurchaseCommitmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_OilAndGasDeliveryCommitmentsAndContractsAxis=sm_NaturalGasPipelineCommitmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_OilAndGasDeliveryCommitmentsAndContractsAxis=sm_CrudeOilPipelineCommitmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

Name:	us-gaap_OilAndGasDeliveryCommitmentsAndContractsAxis=sm_NaturalGasLiquidsPipelineCommitmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

Name:	us-gaap_OtherCommitmentsAxis=sm_DrillingRigLeasingContractsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Commitments and Contingencies (Details) MMcf in Thousands, $ in Millions	Sep. 30, 2017 USD ($) MMcf MMBbls	Nov. 03, 2017 USD ($)	Dec. 31, 2016 USD ($) MMcf MMBbls
Gas gathering and Oil and Gas Through-put Commitments [Member]
Other Commitments [Line Items]
Contractual Obligation \| $	$ 445.0
Water Pipeline Commitment [Member]
Other Commitments [Line Items]
Water Delivery Commitments and Contracts, Remaining Contractual Volume	25
Water Purchase Commitment [Member]
Other Commitments [Line Items]
Long-term Purchase Commitment, Minimum Volume Required	16
Natural Gas Pipeline Commitment [Member]
Other Commitments [Line Items]
Oil and Gas Delivery Commitments and Contracts, Remaining Contractual Volume \| MMcf	850
Crude Oil Pipeline Commitment [Member]
Other Commitments [Line Items]
Oil and Gas Delivery Commitments and Contracts, Remaining Contractual Volume	15
Non-Operated Eagle Ford Divestiture 2017 [Member] \| Gas gathering and Oil and Gas Through-put Commitments [Member]
Other Commitments [Line Items]
Contractual Obligation, potential undiscounted deficiency payments, Non-Operated Eagle Ford Assets \| $			$ 501.9
Non-Operated Eagle Ford Divestiture 2017 [Member] \| Natural Gas Pipeline Commitment [Member]
Other Commitments [Line Items]
Oil and Gas Delivery Commitments and Contracts, Remaining Contractual Volume on Non-Operated Eagle Ford Assets \| MMcf			514
Non-Operated Eagle Ford Divestiture 2017 [Member] \| Crude Oil Pipeline Commitment [Member]
Other Commitments [Line Items]
Oil and Gas Delivery Commitments and Contracts, Remaining Contractual Volume on Non-Operated Eagle Ford Assets			52
Non-Operated Eagle Ford Divestiture 2017 [Member] \| Natural Gas Liquids Pipeline Commitment [Member]
Other Commitments [Line Items]
Oil and Gas Delivery Commitments and Contracts, Remaining Contractual Volume on Non-Operated Eagle Ford Assets			13
Subsequent Event [Member] \| Drilling Rig Leasing Contracts [Member]
Other Commitments [Line Items]
Contractual Obligation \| $		$ 30.4
Early Termination Penalty for Rig Contract Cancellation \| $		$ 17.5