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v3.19.3

Proved and Unproved Oil and Gas Properties and Other Property and Equipment (Details) - USD ($) $ in Thousands | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2019 | Sep. 30, 2018 | Sep. 30, 2019 | Sep. 30, 2018
Fair Value Disclosures [Abstract] |  |  |  |
Abandonment and impairment of unproved properties | $ 6,337 | $ 9,055 | $ 25,092 | $ 26,615

X
- Definition Impairment of Unproved Oil and Gas Properties + References No definition available. + Details
Name: | sm_ImpairmentofUnprovedOilandGasProperties
Namespace Prefix: | sm_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

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