Rose Rock Midstream, L.P. - Summarized balance sheet information (Details) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Summarized Balance Sheet Information
Other current assets	$ 25,445	$ 19,387
Property, plant and equipment, net	1,648,962	1,566,821
Equity method investments	446,938	551,078
Goodwill	34,698	48,032
Other noncurrent assets, net	44,156	45,374
Total assets	3,096,974	2,853,909
Current liabilities	443,963	377,027
Long-term debt, net	1,070,363	1,057,816
Total liabilities and owners’ equity	3,096,974	2,853,909
Rose Rock Midstream, L.P. [Member]
Summarized Balance Sheet Information
Cash	7,909	9,059
Other current assets	413,625	310,555
Property, plant and equipment, net	443,327	441,596
Equity method investments	427,961	438,291
Goodwill	26,628	26,628
Other noncurrent assets, net	17,978	19,461
Total assets	1,337,428	1,245,590
Current liabilities	356,248	283,029
Long-term debt, net	774,488	732,356
Partners’ capital attributable to SemGroup	135,609	149,376
Partners’ capital attributable to noncontrolling interests	71,083	80,829
Total liabilities and owners’ equity	$ 1,337,428	$ 1,245,590