Document and Entity Information Document (USD $)	12 Months Ended
	Dec. 31, 2013	Feb. 12, 2014	Jun. 28, 2013
Document and Entity Information [Abstract]
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-K
Document Period End Date	Dec. 31, 2013
Document Fiscal Year Focus	2013
Document Fiscal Period Focus	FY
Amendment Flag	false
Common Stock, Shares, Outstanding		67,056,441
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Public Float			$ 3,929,174,218.54