Document and Entity Information Document - shares	9 Months Ended
	Sep. 30, 2016	Oct. 26, 2016
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, 2016
Document Fiscal Year Focus	2016
Document Fiscal Period Focus	Q3
Amendment Flag	false
Entity Common Stock, Shares Outstanding		86,869,269
Entity Current Reporting Status	Yes