Rose Rock Midstream, L.P. (Details 3) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Summarized Balance Sheet Information
Other current assets	$ 17,998	$ 28,396
Property, plant and equipment, net	800,231	733,925
Other noncurrent assets, net	17,744	21,875
Total assets	1,711,065	1,491,181
Current liabilities	366,539	296,511
Long-term debt	189,569	83,277
Partners' capital attributable to SemGroup	871,442	851,096
Partners' capital attributable to noncontrolling interests	129,910	127,569
Total liabilities and owners' equity	1,711,065	1,491,181
Rose Rock Midstream, L.P. [Member]
Summarized Balance Sheet Information
Cash	13,498	9,709
Other current assets	236,144	156,873
Property, plant and equipment, net	285,244	276,246
Other noncurrent assets, net	2,665	2,666
Total assets	537,551	445,494
Current liabilities	227,131	140,553
Long-term debt	69	87
Partners' capital attributable to SemGroup	180,441	177,323
Partners' capital attributable to noncontrolling interests	129,910	127,531
Total liabilities and owners' equity	$ 537,551	$ 445,494