Early Termination Penalty for Rig Contract Cancellation

No definition available.

Name:	sm_EarlyTerminationPenaltyforRigContractCancellation
Namespace Prefix:	sm_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
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://fasb.org/us-gaap/role/ref/legacyRef
-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_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_OtherCommitmentsAxis=sm_PipelineCommitmentsMember
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:

- Details

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

- Details

Name:	us-gaap_OtherCommitmentsAxis=sm_ElectricityPurchaseAgreementMember
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_OilAndGasDeliveryCommitmentsAndContractsAxis=sm_NaturalGasPipelineCommitmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Commitments (Details) $ in Millions	Sep. 30, 2018 USD ($) MMBbls Bcf	Nov. 02, 2018 USD ($)
Water Pipeline Commitment [Member]
Other Commitments [Line Items]
Water delivery commitments, remaining minimum contractual volumes \| MMBbls	22
Water Purchase Commitment [Member]
Other Commitments [Line Items]
Water purchase commitment, minimum volume required \| MMBbls	7
Gas gathering and Oil and Gas Through-put Commitments [Member]
Other Commitments [Line Items]
Contractual obligation	$ 342.2
Drilling Rig Leasing Contracts [Member] \| Subsequent Event [Member]
Other Commitments [Line Items]
Contractual obligation		$ 93.0
Early termination penalties for rig contracts		$ 42.7
Electricity Purchase Agreement [Member]
Other Commitments [Line Items]
Contractual obligation	$ 29.9
Crude Oil Pipeline Commitment [Member]
Other Commitments [Line Items]
Oil and gas delivery commitments, remaining minimum contractual volumes \| MMBbls	30
Natural Gas Pipeline Commitment [Member]
Other Commitments [Line Items]
Oil and gas delivery commitments, remaining minimum contractual volumes \| Bcf	691