XML 50 R39.htm IDEA: XBRL DOCUMENT
v3.21.1

Credit Facility and Derivative Counterparties (Details) | Mar. 31, 2021
--- | ---
Derivative Instruments Not Designated as Hedging Instruments [Abstract] |
Percentage of proved property secured for credit facility borrowing | 85.00%

X
- Definition Percentage of Proved Property Secured for Credit Facility Borrowing + References No definition available. + Details
Name: | sm_PercentageofProvedPropertySecuredforCreditFacilityBorrowing
Namespace Prefix: | sm_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- References No definition available. + Details
Name: | us-gaap_DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration