Document and Entity Information Document	9 Months Ended
	Sep. 30, 2014	Oct. 22, 2014
Entity Information [Line Items]
Entity Registrant Name	SM Energy Co
Entity Central Index Key	0000893538
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Document Type	10-Q
Document Period End Date	Sep. 30, 2014
Document Fiscal Year Focus	2014
Document Fiscal Period Focus	Q3
Amendment Flag	false
Entity Common Stock, Shares Outstanding		67,405,401
Entity Current Reporting Status	Yes