XML 53 R45.htm IDEA: XBRL DOCUMENT
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Long-Term Debt (Details) (USD $) | 12 Months Ended |  |  |  |  |
--- | --- | --- | --- | --- | --- | ---
Dec. 31, 2014 | Dec. 31, 2013 | Dec. 31, 2012 | Dec. 31, 2011 | Nov. 17, 2014 | May 20, 2013 | Jun. 29, 2012 | Nov. 08, 2011 | Feb. 07, 2011
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |
Senior Notes | $ 2,200,000,000 us-gaap_SeniorNotes | $ 1,600,000,000 us-gaap_SeniorNotes |  |  |  |  |  |  |
Debt Conversion, Converted Instrument, Amount |  |  | 2,641,000 us-gaap_StockIssuedDuringPeriodValueConversionOfConvertibleSecurities |  |  |  |  |  |
Interest Costs, Capitalized During Period | 16,200,000 us-gaap_InterestCostsCapitalized | 11,000,000 us-gaap_InterestCostsCapitalized | 12,100,000 us-gaap_InterestCostsCapitalized |  |  |  |  |  |
Senior Notes [Member] |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |
6.625% Senior Notes, Due 2019 Face Value | 350,000,000 sm_A6.625SeniorNotesDue2019FaceValue / us-gaap_LongtermDebtTypeAxis = us-gaap_SeniorNotesMember | 350,000,000 sm_A6.625SeniorNotesDue2019FaceValue / us-gaap_LongtermDebtTypeAxis = us-gaap_SeniorNotesMember |  |  |  |  |  |  |
6.50% Senior Notes, Due 2021 Face Value | 350,000,000 sm_A6.50SeniorNotesDue2021FaceValue / us-gaap_LongtermDebtTypeAxis = us-gaap_SeniorNotesMember | 350,000,000 sm_A6.50SeniorNotesDue2021FaceValue / us-gaap_LongtermDebtTypeAxis = us-gaap_SeniorNotesMember |  |  |  |  |  |  |
6.125% Senior Notes, Due 2022 | 600,000,000 sm_A6.125SeniorNotesDue2022 / us-gaap_LongtermDebtTypeAxis = us-gaap_SeniorNotesMember | 0 sm_A6.125SeniorNotesDue2022 / us-gaap_LongtermDebtTypeAxis = us-gaap_SeniorNotesMember |  |  |  |  |  |  |
6.50% Senior Notes, Due 2023 Face Value | 400,000,000 sm_A6.50SeniorNotesDue2023FaceValue / us-gaap_LongtermDebtTypeAxis = us-gaap_SeniorNotesMember | 400,000,000 sm_A6.50SeniorNotesDue2023FaceValue / us-gaap_LongtermDebtTypeAxis = us-gaap_SeniorNotesMember |  |  |  |  |  |  |
5% Senior Notes, Due 2024 Face Value | 500,000,000 sm_A5SeniorNotesDue2024FaceValue / us-gaap_LongtermDebtTypeAxis = us-gaap_SeniorNotesMember | 500,000,000 sm_A5SeniorNotesDue2024FaceValue / us-gaap_LongtermDebtTypeAxis = us-gaap_SeniorNotesMember |  |  |  |  |  |  |
Senior Notes | 2,200,000,000 us-gaap_SeniorNotes / us-gaap_LongtermDebtTypeAxis = us-gaap_SeniorNotesMember | 1,600,000,000 us-gaap_SeniorNotes / us-gaap_LongtermDebtTypeAxis = us-gaap_SeniorNotesMember |  |  |  |  |  |  |
Debt Instrument, Covenant Compliance, Dividends Excluded From Computation | 6,500,000 sm_DebtInstrumentCovenantComplianceDividendsExcludedFromComputation / us-gaap_LongtermDebtTypeAxis = us-gaap_SeniorNotesMember |  |  |  |  |  |  |  |
Senior Notes [Member] | 6.125% Senior Notes Due 2022 [Member] |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |
Debt Instrument, Face Amount |  |  |  |  | 600,000,000 us-gaap_DebtInstrumentFaceAmount / us-gaap_DebtInstrumentAxis = sm_A6.125SeniorNotesDue2022Member / us-gaap_LongtermDebtTypeAxis = us-gaap_SeniorNotesMember |  |  |  |
Debt Instrument, Interest Rate, Stated Percentage |  |  |  |  | 6.125%us-gaap_DebtInstrumentInterestRateStatedPercentage / us-gaap_DebtInstrumentAxis = sm_A6.125SeniorNotesDue2022Member / us-gaap_LongtermDebtTypeAxis = us-gaap_SeniorNotesMember |  |  |  |
Net proceeds from debt issuance | 590,000,000 us-gaap_ProceedsFromDebtNetOfIssuanceCosts / us-gaap_DebtInstrumentAxis = sm_A6.125SeniorNotesDue2022Member / us-gaap_LongtermDebtTypeAxis = us-gaap_SeniorNotesMember |  |  |  |  |  |  |  |
Deferred Finance Costs, Gross |  |  |  |  | 10,000,000 us-gaap_DeferredFinanceCostsGross / us-gaap_DebtInstrumentAxis = sm_A6.125SeniorNotesDue2022Member / us-gaap_LongtermDebtTypeAxis = us-gaap_SeniorNotesMember |  |  |  |
Maximum percentage of the principal amount of the debt instrument which the entity may redeem with proceeds from equity offerings in the first through third year following the issuance year (as a percent) | 35.00%sm_DebtInstrumentMaximumEarlyRedemptionPercentOfPrincipal / us-gaap_DebtInstrumentAxis = sm_A6.125SeniorNotesDue2022Member / us-gaap_LongtermDebtTypeAxis = us-gaap_SeniorNotesMember |  |  |  |  |  |  |  |
Redemption price of debt instrument if redeemed with proceeds from qualified equity offerings in the first through third year following the issuance year (as a percent) | 106.125%sm_DebtInstrumentFutureRedemptionPriceAsPercentageofPrincipalFirstThroughThirdYear / us-gaap_DebtInstrumentAxis = sm_A6.125SeniorNotesDue2022Member / us-gaap_LongtermDebtTypeAxis = us-gaap_SeniorNotesMember |  |  |  |  |  |  |  |
Debt Instrument, Call Feature | at a redemption price equal to 100 percent of the principal amount of the 2022 Notes to be redeemed, plus a specified make-whole premium and accrued and unpaid interest to the applicable redemption date. |  |  |  |  |  |  |  |
Maximum Penalty as a Percentage of Face Value for Not Registering Senior Notes Within One Year of Issuance |  |  |  |  | 1.00%sm_MaximumPenaltyasaPercentageofFaceValueforNotRegisteringSeniorNotesWithinOneYearofIssuance / us-gaap_DebtInstrumentAxis = sm_A6.125SeniorNotesDue2022Member / us-gaap_LongtermDebtTypeAxis = us-gaap_SeniorNotesMember |  |  |  |
Senior Notes [Member] | 5% Senior Notes Due 2024 [Member] |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |
Debt Instrument, Face Amount |  |  |  |  |  | 500,000,000 us-gaap_DebtInstrumentFaceAmount / us-gaap_DebtInstrumentAxis = sm_A5SeniorNotesDue2024Member / us-gaap_LongtermDebtTypeAxis = us-gaap_SeniorNotesMember |  |  |
Debt Instrument, Interest Rate, Stated Percentage |  |  |  |  |  | 5.00%us-gaap_DebtInstrumentInterestRateStatedPercentage / us-gaap_DebtInstrumentAxis = sm_A5SeniorNotesDue2024Member / us-gaap_LongtermDebtTypeAxis = us-gaap_SeniorNotesMember |  |  |
Net proceeds from debt issuance |  | 490,200,000 us-gaap_ProceedsFromDebtNetOfIssuanceCosts / us-gaap_DebtInstrumentAxis = sm_A5SeniorNotesDue2024Member / us-gaap_LongtermDebtTypeAxis = us-gaap_SeniorNotesMember |  |  |  |  |  |  |
Deferred Finance Costs, Gross |  |  |  |  |  | 9,800,000 us-gaap_DeferredFinanceCostsGross / us-gaap_DebtInstrumentAxis = sm_A5SeniorNotesDue2024Member / us-gaap_LongtermDebtTypeAxis = us-gaap_SeniorNotesMember |  |  |
Redemption price of debt instrument if redeemed with proceeds from qualified equity offerings in the first through third year following the issuance year (as a percent) | 105.00%sm_DebtInstrumentFutureRedemptionPriceAsPercentageofPrincipalFirstThroughThirdYear / us-gaap_DebtInstrumentAxis = sm_A5SeniorNotesDue2024Member / us-gaap_LongtermDebtTypeAxis = us-gaap_SeniorNotesMember |  |  |  |  |  |  |  |
Debt Instrument, Call Feature | at a redemption price equal to 100 percent of the principal amount of the 2024 Notes to be redeemed, plus a specified make-whole premium and accrued and unpaid interest to the applicable redemption date. |  |  |  |  |  |  |  |
Senior Notes [Member] | 6.50% Senior Notes Due 2023 [Member] |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |
Debt Instrument, Face Amount |  |  |  |  |  |  | 400,000,000 us-gaap_DebtInstrumentFaceAmount / us-gaap_DebtInstrumentAxis = sm_A650SeniorNotesDue2023Member / us-gaap_LongtermDebtTypeAxis = us-gaap_SeniorNotesMember |  |
Debt Instrument, Interest Rate, Stated Percentage |  |  |  |  |  |  | 6.50%us-gaap_DebtInstrumentInterestRateStatedPercentage / us-gaap_DebtInstrumentAxis = sm_A650SeniorNotesDue2023Member / us-gaap_LongtermDebtTypeAxis = us-gaap_SeniorNotesMember |  |
Net proceeds from debt issuance |  |  | 392,100,000 us-gaap_ProceedsFromDebtNetOfIssuanceCosts / us-gaap_DebtInstrumentAxis = sm_A650SeniorNotesDue2023Member / us-gaap_LongtermDebtTypeAxis = us-gaap_SeniorNotesMember |  |  |  |  |  |
Deferred Finance Costs, Gross |  |  |  |  |  |  | 7,900,000 us-gaap_DeferredFinanceCostsGross / us-gaap_DebtInstrumentAxis = sm_A650SeniorNotesDue2023Member / us-gaap_LongtermDebtTypeAxis = us-gaap_SeniorNotesMember |  |
Maximum percentage of the principal amount of the debt instrument which the entity may redeem with proceeds from equity offerings in the first through third year following the issuance year (as a percent) | 35.00%sm_DebtInstrumentMaximumEarlyRedemptionPercentOfPrincipal / us-gaap_DebtInstrumentAxis = sm_A650SeniorNotesDue2023Member / us-gaap_LongtermDebtTypeAxis = us-gaap_SeniorNotesMember |  |  |  |  |  |  |  |
Redemption price of debt instrument if redeemed with proceeds from qualified equity offerings in the first through third year following the issuance year (as a percent) | 106.50%sm_DebtInstrumentFutureRedemptionPriceAsPercentageofPrincipalFirstThroughThirdYear / us-gaap_DebtInstrumentAxis = sm_A650SeniorNotesDue2023Member / us-gaap_LongtermDebtTypeAxis = us-gaap_SeniorNotesMember |  |  |  |  |  |  |  |
Debt Instrument, Call Feature | redemption price equal to 100 percent of the principal amount of the 2023 Notes to be redeemed, plus a specified make-whole premium and accrued and unpaid interest to the applicable redemption date. |  |  |  |  |  |  |  |
Senior Notes [Member] | 6.50% Senior Notes Due 2021 [Member] |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |
Debt Instrument, Face Amount |  |  |  |  |  |  |  | 350,000,000 us-gaap_DebtInstrumentFaceAmount / us-gaap_DebtInstrumentAxis = sm_A650SeniorNotesDue2021Member / us-gaap_LongtermDebtTypeAxis = us-gaap_SeniorNotesMember |
Debt Instrument, Interest Rate, Stated Percentage |  |  |  |  |  |  |  | 6.50%us-gaap_DebtInstrumentInterestRateStatedPercentage / us-gaap_DebtInstrumentAxis = sm_A650SeniorNotesDue2021Member / us-gaap_LongtermDebtTypeAxis = us-gaap_SeniorNotesMember |
Net proceeds from debt issuance |  |  |  | 343,100,000 us-gaap_ProceedsFromDebtNetOfIssuanceCosts / us-gaap_DebtInstrumentAxis = sm_A650SeniorNotesDue2021Member / us-gaap_LongtermDebtTypeAxis = us-gaap_SeniorNotesMember |  |  |  |  |
Deferred Finance Costs, Gross |  |  |  |  |  |  |  | 6,900,000 us-gaap_DeferredFinanceCostsGross / us-gaap_DebtInstrumentAxis = sm_A650SeniorNotesDue2021Member / us-gaap_LongtermDebtTypeAxis = us-gaap_SeniorNotesMember |
Debt Instrument, Call Feature | redemption price equal to 100 percent of the principal amount, plus a specified make-whole premium and accrued and unpaid interest |  |  |  |  |  |  |  |
Senior Notes [Member] | 6.625% Senior Notes Due 2019 [Member] |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |
Debt Instrument, Face Amount |  |  |  |  |  |  |  |  | 350,000,000 us-gaap_DebtInstrumentFaceAmount / us-gaap_DebtInstrumentAxis = sm_A6625SeniorNotesDue2019Member / us-gaap_LongtermDebtTypeAxis = us-gaap_SeniorNotesMember
Debt Instrument, Interest Rate, Stated Percentage |  |  |  |  |  |  |  |  | 6.625%us-gaap_DebtInstrumentInterestRateStatedPercentage / us-gaap_DebtInstrumentAxis = sm_A6625SeniorNotesDue2019Member / us-gaap_LongtermDebtTypeAxis = us-gaap_SeniorNotesMember
Net proceeds from debt issuance |  |  |  | 341,100,000 us-gaap_ProceedsFromDebtNetOfIssuanceCosts / us-gaap_DebtInstrumentAxis = sm_A6625SeniorNotesDue2019Member / us-gaap_LongtermDebtTypeAxis = us-gaap_SeniorNotesMember |  |  |  |  |
Deferred Finance Costs, Gross |  |  |  |  |  |  |  |  | 8,900,000 us-gaap_DeferredFinanceCostsGross / us-gaap_DebtInstrumentAxis = sm_A6625SeniorNotesDue2019Member / us-gaap_LongtermDebtTypeAxis = us-gaap_SeniorNotesMember
Senior Notes [Member] | 2015 [Member] | 6.625% Senior Notes Due 2019 [Member] |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |
Early Debt Redemption, Redemption Price as a Percent of Face Amount | 103.313%sm_EarlyDebtRedemptionRedemptionPriceAsPercentOfFaceAmount / us-gaap_DebtInstrumentAxis = sm_A6625SeniorNotesDue2019Member / sm_EarlyDebtRedemptionYearAxis = sm_A2015Member / us-gaap_LongtermDebtTypeAxis = us-gaap_SeniorNotesMember |  |  |  |  |  |  |  |
Senior Notes [Member] | 2016 [Member] | 6.50% Senior Notes Due 2021 [Member] |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |
Early Debt Redemption, Redemption Price as a Percent of Face Amount | 103.25%sm_EarlyDebtRedemptionRedemptionPriceAsPercentOfFaceAmount / us-gaap_DebtInstrumentAxis = sm_A650SeniorNotesDue2021Member / sm_EarlyDebtRedemptionYearAxis = sm_A2016Member / us-gaap_LongtermDebtTypeAxis = us-gaap_SeniorNotesMember |  |  |  |  |  |  |  |
Senior Notes [Member] | 2016 [Member] | 6.625% Senior Notes Due 2019 [Member] |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |
Early Debt Redemption, Redemption Price as a Percent of Face Amount | 101.656%sm_EarlyDebtRedemptionRedemptionPriceAsPercentOfFaceAmount / us-gaap_DebtInstrumentAxis = sm_A6625SeniorNotesDue2019Member / sm_EarlyDebtRedemptionYearAxis = sm_A2016Member / us-gaap_LongtermDebtTypeAxis = us-gaap_SeniorNotesMember |  |  |  |  |  |  |  |
Senior Notes [Member] | 2017 [Member] | 6.50% Senior Notes Due 2023 [Member] |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |
Early Debt Redemption, Redemption Price as a Percent of Face Amount | 103.25%sm_EarlyDebtRedemptionRedemptionPriceAsPercentOfFaceAmount / us-gaap_DebtInstrumentAxis = sm_A650SeniorNotesDue2023Member / sm_EarlyDebtRedemptionYearAxis = sm_A2017Member / us-gaap_LongtermDebtTypeAxis = us-gaap_SeniorNotesMember |  |  |  |  |  |  |  |
Senior Notes [Member] | 2017 [Member] | 6.50% Senior Notes Due 2021 [Member] |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |
Early Debt Redemption, Redemption Price as a Percent of Face Amount | 102.167%sm_EarlyDebtRedemptionRedemptionPriceAsPercentOfFaceAmount / us-gaap_DebtInstrumentAxis = sm_A650SeniorNotesDue2021Member / sm_EarlyDebtRedemptionYearAxis = sm_A2017Member / us-gaap_LongtermDebtTypeAxis = us-gaap_SeniorNotesMember |  |  |  |  |  |  |  |
Senior Notes [Member] | 2018 [Member] | 6.125% Senior Notes Due 2022 [Member] |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |
Early Debt Redemption, Redemption Price as a Percent of Face Amount | 103.063%sm_EarlyDebtRedemptionRedemptionPriceAsPercentOfFaceAmount / us-gaap_DebtInstrumentAxis = sm_A6.125SeniorNotesDue2022Member / sm_EarlyDebtRedemptionYearAxis = sm_A2018Member / us-gaap_LongtermDebtTypeAxis = us-gaap_SeniorNotesMember |  |  |  |  |  |  |  |
Senior Notes [Member] | 2018 [Member] | 5% Senior Notes Due 2024 [Member] |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |
Early Debt Redemption, Redemption Price as a Percent of Face Amount | 102.50%sm_EarlyDebtRedemptionRedemptionPriceAsPercentOfFaceAmount / us-gaap_DebtInstrumentAxis = sm_A5SeniorNotesDue2024Member / sm_EarlyDebtRedemptionYearAxis = sm_A2018Member / us-gaap_LongtermDebtTypeAxis = us-gaap_SeniorNotesMember |  |  |  |  |  |  |  |
Senior Notes [Member] | 2018 [Member] | 6.50% Senior Notes Due 2023 [Member] |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |
Early Debt Redemption, Redemption Price as a Percent of Face Amount | 102.167%sm_EarlyDebtRedemptionRedemptionPriceAsPercentOfFaceAmount / us-gaap_DebtInstrumentAxis = sm_A650SeniorNotesDue2023Member / sm_EarlyDebtRedemptionYearAxis = sm_A2018Member / us-gaap_LongtermDebtTypeAxis = us-gaap_SeniorNotesMember |  |  |  |  |  |  |  |
Senior Notes [Member] | 2018 [Member] | 6.50% Senior Notes Due 2021 [Member] |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |
Early Debt Redemption, Redemption Price as a Percent of Face Amount | 101.083%sm_EarlyDebtRedemptionRedemptionPriceAsPercentOfFaceAmount / us-gaap_DebtInstrumentAxis = sm_A650SeniorNotesDue2021Member / sm_EarlyDebtRedemptionYearAxis = sm_A2018Member / us-gaap_LongtermDebtTypeAxis = us-gaap_SeniorNotesMember |  |  |  |  |  |  |  |
Senior Notes [Member] | 2019 [Member] | 6.125% Senior Notes Due 2022 [Member] |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |
Early Debt Redemption, Redemption Price as a Percent of Face Amount | 101.531%sm_EarlyDebtRedemptionRedemptionPriceAsPercentOfFaceAmount / us-gaap_DebtInstrumentAxis = sm_A6.125SeniorNotesDue2022Member / sm_EarlyDebtRedemptionYearAxis = sm_A2019Member / us-gaap_LongtermDebtTypeAxis = us-gaap_SeniorNotesMember |  |  |  |  |  |  |  |
Senior Notes [Member] | 2019 [Member] | 5% Senior Notes Due 2024 [Member] |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |
Early Debt Redemption, Redemption Price as a Percent of Face Amount | 101.677%sm_EarlyDebtRedemptionRedemptionPriceAsPercentOfFaceAmount / us-gaap_DebtInstrumentAxis = sm_A5SeniorNotesDue2024Member / sm_EarlyDebtRedemptionYearAxis = sm_A2019Member / us-gaap_LongtermDebtTypeAxis = us-gaap_SeniorNotesMember |  |  |  |  |  |  |  |
Senior Notes [Member] | 2019 [Member] | 6.50% Senior Notes Due 2023 [Member] |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |
Early Debt Redemption, Redemption Price as a Percent of Face Amount | 101.083%sm_EarlyDebtRedemptionRedemptionPriceAsPercentOfFaceAmount / us-gaap_DebtInstrumentAxis = sm_A650SeniorNotesDue2023Member / sm_EarlyDebtRedemptionYearAxis = sm_A2019Member / us-gaap_LongtermDebtTypeAxis = us-gaap_SeniorNotesMember |  |  |  |  |  |  |  |
Senior Notes [Member] | 2020 [Member] | 5% Senior Notes Due 2024 [Member] |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |
Early Debt Redemption, Redemption Price as a Percent of Face Amount | 100.833%sm_EarlyDebtRedemptionRedemptionPriceAsPercentOfFaceAmount / us-gaap_DebtInstrumentAxis = sm_A5SeniorNotesDue2024Member / sm_EarlyDebtRedemptionYearAxis = sm_A2020Member / us-gaap_LongtermDebtTypeAxis = us-gaap_SeniorNotesMember |  |  |  |  |  |  |  |
Senior Notes [Member] | 2020 and Thereafter [Member] | 6.125% Senior Notes Due 2022 [Member] |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |
Early Debt Redemption, Redemption Price as a Percent of Face Amount | 100.00%sm_EarlyDebtRedemptionRedemptionPriceAsPercentOfFaceAmount / us-gaap_DebtInstrumentAxis = sm_A6.125SeniorNotesDue2022Member / sm_EarlyDebtRedemptionYearAxis = sm_A2020andThereafterMember / us-gaap_LongtermDebtTypeAxis = us-gaap_SeniorNotesMember |  |  |  |  |  |  |  |
Senior Notes [Member] | 2020 and Thereafter [Member] | 6.50% Senior Notes Due 2023 [Member] |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |
Early Debt Redemption, Redemption Price as a Percent of Face Amount | 100.00%sm_EarlyDebtRedemptionRedemptionPriceAsPercentOfFaceAmount / us-gaap_DebtInstrumentAxis = sm_A650SeniorNotesDue2023Member / sm_EarlyDebtRedemptionYearAxis = sm_A2020andThereafterMember / us-gaap_LongtermDebtTypeAxis = us-gaap_SeniorNotesMember |  |  |  |  |  |  |  |
Senior Notes [Member] | 2019 and Thereafter [Member] | 6.50% Senior Notes Due 2021 [Member] |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |
Early Debt Redemption, Redemption Price as a Percent of Face Amount | 100.00%sm_EarlyDebtRedemptionRedemptionPriceAsPercentOfFaceAmount / us-gaap_DebtInstrumentAxis = sm_A650SeniorNotesDue2021Member / sm_EarlyDebtRedemptionYearAxis = sm_A2019AndThereafterMember / us-gaap_LongtermDebtTypeAxis = us-gaap_SeniorNotesMember |  |  |  |  |  |  |  |
Senior Notes [Member] | 2017 and Thereafter [Member] | 6.625% Senior Notes Due 2019 [Member] |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |
Early Debt Redemption, Redemption Price as a Percent of Face Amount | 100.00%sm_EarlyDebtRedemptionRedemptionPriceAsPercentOfFaceAmount / us-gaap_DebtInstrumentAxis = sm_A6625SeniorNotesDue2019Member / sm_EarlyDebtRedemptionYearAxis = sm_A2017AndThereafterMember / us-gaap_LongtermDebtTypeAxis = us-gaap_SeniorNotesMember |  |  |  |  |  |  |  |
Senior Notes [Member] | 2021 and Thereafter [Member] | 5% Senior Notes Due 2024 [Member] |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |
Early Debt Redemption, Redemption Price as a Percent of Face Amount | 100.00%sm_EarlyDebtRedemptionRedemptionPriceAsPercentOfFaceAmount / us-gaap_DebtInstrumentAxis = sm_A5SeniorNotesDue2024Member / sm_EarlyDebtRedemptionYearAxis = sm_A2021AndThereafterMember / us-gaap_LongtermDebtTypeAxis = us-gaap_SeniorNotesMember |  |  |  |  |  |  |  |
Convertible Debt [Member] | 3.50% Senior Convertible Notes |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |
Debt Instrument, Interest Rate, Stated Percentage |  |  | 3.50%us-gaap_DebtInstrumentInterestRateStatedPercentage / us-gaap_DebtInstrumentAxis = us-gaap_ConvertibleDebtMember / us-gaap_LongtermDebtTypeAxis = us-gaap_ConvertibleDebtMember |  |  |  |  |  |
Conversion of 3.50% Senior Convertible Notes to common stock, including income tax benefit of conversion (shares) |  |  | 864,106 us-gaap_StockIssuedDuringPeriodSharesConversionOfConvertibleSecurities / us-gaap_DebtInstrumentAxis = us-gaap_ConvertibleDebtMember / us-gaap_LongtermDebtTypeAxis = us-gaap_ConvertibleDebtMember |  |  |  |  |  |
Debt Conversion, Converted Instrument, Amount |  |  | 281,300,000 us-gaap_StockIssuedDuringPeriodValueConversionOfConvertibleSecurities / us-gaap_DebtInstrumentAxis = us-gaap_ConvertibleDebtMember / us-gaap_LongtermDebtTypeAxis = us-gaap_ConvertibleDebtMember |  |  |  |  |  |
Repayments of Convertible Debt |  |  | $ 6,200,000 us-gaap_RepaymentsOfConvertibleDebt / us-gaap_DebtInstrumentAxis = us-gaap_ConvertibleDebtMember / us-gaap_LongtermDebtTypeAxis = us-gaap_ConvertibleDebtMember |  |  |  |  |  |

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- Definition 5% Senior Notes, Due 2024 + References No definition available. + Details
Name: | sm_A5SeniorNotesDue2024FaceValue
Namespace Prefix: | sm_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

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- Definition 6.125% Senior Notes, Due 2022 + References No definition available. + Details
Name: | sm_A6.125SeniorNotesDue2022
Namespace Prefix: | sm_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

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- Definition Carrying value as of the balance sheet date of 6.50% Notes due 2021 with the highest claim on the assets of the issuer in case of bankruptcy or liquidation (with maturities initially due after one year or beyond the operating cycle if longer), excluding current portion. Senior note holders are paid off in full before any payments are made to junior note holders. + References No definition available. + Details
Name: | sm_A6.50SeniorNotesDue2021FaceValue
Namespace Prefix: | sm_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

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- Definition Carrying value as of the balance sheet date of 6.50% Notes due 2021 with the highest claim on the assets of the issuer in case of bankruptcy or liquidation (with maturities initially due after one year or beyond the operating cycle if longer), excluding current portion. Senior note holders are paid off in full before any payments are made to junior note holders. + References No definition available. + Details
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- Definition Carrying value as of the balance sheet date of 6.625% Notes with the highest claim on the assets of the issuer in case of bankruptcy or liquidation (with maturities initially due after one year or beyond the operating cycle if longer), excluding current portion. Senior note holders are paid off in full before any payments are made to junior note holders. + References No definition available. + Details
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- Definition Description of a feature that permits the issuer of the debt to repay or convert it before the stated maturity date (early retirement date). The description may include such items as the call price, the period that the issuer can call the debt, including the earliest call date, and other significant terms of the call feature, which may include the debt holders' ability to convert the debt to equity if the call option is exercised and contingent events that trigger the issuer's ability to call the debt. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 22 -Article 5 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 470 -Section 50 -Paragraph 3 -Subparagraph (e) -URI http://asc.fasb.org/extlink&oid=6479336&loc=d3e64711-112823 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.22(a)(5)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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- Definition Contractual interest rate for funds borrowed, under the debt agreement. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 22 -Article 5 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.22(a)(1)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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- Definition For an unclassified balance sheet, the amount as of the balance sheet date of capitalized costs associated with the issuance of debt instruments (for example, legal, accounting, underwriting, printing, and registration costs) that will be charged against earnings over the life of the debt instruments to which such costs pertain. Such amount is before the consideration of accumulated amortization. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 835 -SubTopic 30 -Section 45 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=6451184&loc=d3e28555-108399 + Details
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