Rose Rock Midstream, L.P. (Details 3) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Summarized Balance Sheet Information
Other current assets	$ 13,392	$ 18,516
Property, plant and equipment, net	817,141	814,724
Equity method investment	423,507	387,802
Other noncurrent assets, net	30,969	8,181
Total assets	1,809,208	1,748,179
Current liabilities	380,282	374,344
Long-term debt	176,056	206,062
Partners' capital attributable to SemGroup	988,228	892,394
Partners' capital attributable to noncontrolling interests	98,166	129,134
Total liabilities and owners' equity	1,809,208	1,748,179
Rose Rock Midstream, L.P. [Member]
Summarized Balance Sheet Information
Cash	2,369	108
Other current assets	257,415	250,509
Property, plant and equipment, net	295,384	291,530
Equity method investment	54,459	0
Other noncurrent assets, net	3,992	2,579
Total assets	613,619	544,726
Current liabilities	234,266	231,843
Long-term debt	152,556	4,562
Partners' capital attributable to SemGroup	128,631	179,187
Partners' capital attributable to noncontrolling interests	98,166	129,134
Total liabilities and owners' equity	$ 613,619	$ 544,726