v2.4.0.6

Impairment of Proved and Unproved Properties	9 Months Ended
	Sep. 30, 2012
Impairment of Proved and Unproved Properties [Abstract]
Asset Impairment Charges [Text Block]	Note 13 - Impairment of Proved and Unproved Properties Proved Properties     For the nine months ended September 30, 2012, the Company recorded $38.5 million of proved property impairments on the Company's Haynesville shale assets, due to a decline in natural gas prices during the second quarter of 2012. For the nine months ended September 30, 2011, the Company recorded $48.5 million of proved property impairments on the Company's James Lime assets, due primarily to low natural gas prices. Unproved Properties For the nine months ended September 30, 2012, the Company recorded $11.3 million of abandonment and impairment of unproved properties related to acreage that the Company no longer intends to develop within its Rocky Mountain region. For the nine months ended September 30, 2011, the Company recorded $4.3 million of abandonment and impairment of unproved properties associated with lease expirations in its Mid-Continent region.

X

- Details

Name:	sm_ImpairmentOfProvedAndUnprovedPropertiesAbstract
Namespace Prefix:	sm_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

X

- Definition

The entire disclosure for the details of the charge against earnings resulting from the aggregate write down of all assets from their carrying value to their fair value. Disclosure may also include a description of the impaired asset and facts and circumstances leading to the impairment, amount of the impairment loss and where the loss is located in the income statement, method(s) for determining fair value, and the segment in which the impaired asset is reported.

+ References

No definition available.

+ Details

Name:	us-gaap_AssetImpairmentChargesTextBlock
Namespace Prefix:	us-gaap_
Data Type:	nonnum:textBlockItemType
Balance Type:	na
Period Type:	duration