Document and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2017	Jan. 31, 2018	Jun. 30, 2017
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2017
Document Fiscal Period Focus	FY
Document Fiscal Year Focus	2017
Entity Registrant Name	SemGroup Corporation
Entity Central Index Key	0001489136
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Well-known Seasoned Issuer	Yes
Entity Public Float			$ 1,774,066,887
Entity Current Reporting Status	No
Entity Voluntary Filers	No
Class A [Member]
Entity Common Stock, Shares Outstanding		78,672,995
Class B
Entity Common Stock, Shares Outstanding		0