Rose Rock Midstream, L.P. - Summarized balance sheet information (Details) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Summarized Balance Sheet Information
Other current assets	$ 18,754	$ 19,387
Property, plant and equipment, net	1,629,751	1,566,821
Equity method investments	503,914	551,078
Goodwill	35,008	48,032
Other noncurrent assets, net	24,561	45,374
Total assets	2,801,832	2,853,909
Current liabilities	316,726	377,027
Long-term debt, net	1,122,588	1,057,816
Total liabilities and owners’ equity	2,801,832	2,853,909
Rose Rock Midstream, L.P. [Member]
Summarized Balance Sheet Information
Cash	10,672	9,059
Other current assets	279,802	310,555
Property, plant and equipment, net	443,415	441,596
Equity method investments	433,572	438,291
Goodwill	26,628	26,628
Other noncurrent assets, net	18,748	19,461
Total assets	1,212,837	1,245,590
Current liabilities	229,164	283,029
Long-term debt, net	756,921	732,356
Partners’ capital attributable to SemGroup	147,218	149,376
Partners’ capital attributable to noncontrolling interests	79,534	80,829
Total liabilities and owners’ equity	$ 1,212,837	$ 1,245,590